Waterproofing & Thermal Insulation Glossary
Abrasion Resistance: the ability of a material to resist being worn away by
Contact with another moving, abrasive surface, such as foot traffic, mechanical
Equipment, wind-blown particles, etc.

Absorption: the ability of a material to accept within its body quantities of gases
Or liquid, such as moisture.

AAMA: American Architectural Manufacturers Association.

Abrasion Resistance: the ability of a material to resist being worn away by
Contact with another moving, abrasive surface, such as foot traffic, mechanical
Equipment, wind-blown particles, etc.

Absorption: the ability of a material to accept within its body quantities of gases
Or liquid, such as moisture.

Accelerated Weathering: the process in which materials are exposed to a
Controlled environment where various exposures such as heat, water,
Condensation, or light are altered to magnify their effects, thereby accelerating
The weathering process. The material's physical properties are measured after
This process and compared to the original properties of the unexposed material,
Or to the properties of the material that has been exposed to natural weathering.

ACI: American Concrete Institute.
Acid Etch: in waterproofing, use of a strong acid to cut away and remove the Surface of concrete to expose the aggregate.

ACIL: American Council of Independent Laboratories.
Acrylic Coating: a coating system based on an acrylic resin. Generally, latex
Based Coating system which cures by air drying.
Acrylic Resin: polymers of acrylic or methacrylic monomers. Often used as a
Latex base for coating systems.
Active: will corrode in the presence of moisture or a "noble" metal.
Adhere: to cause two surfaces to be held together by adhesion, typically with
Asphalt or roofing cements in built-up roofing and with contact cements in some
Single-ply membranes.
Adhesion: the state in which two surfaces are held together by interracial forces
Which may consist of molecular forces or interlocking action, or both.
AFA: American Fiberboard Association.
AGO: Associated General Contractors of America.
Aggregate: rock, stone, crushed stone, crushed slag, water-worn gravel or
Marble chips used for surfacing and/or ballasting a roof system.
Aging: the effect on materials that are exposed to an environment for an interval
Of time.

AHA: American Hardboard Association.
AIA: American Institute of Architects.
Air Leakage: (as it relates to passive ventilation) negative condition where air
Leaks into the roof cavity (designed for use as a passive ventilation system)
Through cracks or openings in the structure in lieu of through the intended intake
Vents.
Alligatoring: the cracking of the surfacing bitumen on a built-up roof, producing
A pattern of cracks similar to an alligator's hide; the cracks may or may not
Extend through the surfacing bitumen.
Aluminized Steel: sheet steel with a thin aluminum coating bonded to the
Surface to enhance weathering characteristics.
Aluminum: a non-rusting metal sometimes used for metal roofing and flashing.
Ambient Temperature: the temperature of the air; air temperature.
Anodic: when two metals are connected in an electrolyte, they will form a
Galvanic cell, with the higher metal in the galvanic series being the anode. The
Anodic oxidizes and produces an electrical current to protect the cathode from
Corrosion.

ANSI: American National Standards Institute.
APA: American Plywood Association.
APP: see Atactic Polypropylene.
Application Rate: the quantity (mass, volume, or thickness) of material applied
per unit area.
Apron Flashing: a term used for a flashing located at the juncture of the top of
The sloped roof and a vertical wall or steeper-sloped roof.
Architectural Panel: a metal roof panel, typically a double standing seam or
Batten seam; usually requires solid decking underneath and relies on slope to
Shed water.
Architectural Shingle: shingle that provides a dimensional appearance.
Area Divider: a raised, flashed assembly (typically a single- or double-wood
Member attached to a wood base plate) that is anchored to the roof deck. It is
Used to relieve thermal stresses in a roof system where an expansion joint is not
Required, or to separate large roof areas (sometimes between expansion joints),
And may be used to facilitate installation of tapered insulation. (See NRCA
Construction Details.)
ARMA: Asphalt Roofing Manufacturers Association.
ASA: American Subcontractors Association.
Asbestos: a group of natural, fibrous, impure silicate materials used to reinforce
Some roofing products.
ASC: Associated Specialty Contractors.
ASHI: American Society of Home Inspectors.
ASHRAE: American Society of Heating, Refrigerating & Air-Conditioning
Engineers, Inc.
Asphalt: a dark brown or black substance found in a natural state or, more
Commonly, left as a residue after evaporating or otherwise processing crude oil
Or petroleum. Asphalt may be further refined to conform to various roofing grade
Specifications:
Dead-Level Asphalt: roofing asphalt conforming to the requirements of ASTM
Specification D 312, Type I.
Flat Asphalt: roofing asphalt conforming to the requirements of ASTM
Specification D 312, Type II.
Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM
Specification D 312, Type lilt.
Special Steep Asphalt: roofing asphalt conforming to the requirements of ASTM
Specification D 312, Type IV.
Asphalt, Air Blown: produced by blowing air through molten asphalt held at an
Elevated temperature, to raise the asphalt's softening point and modify other
Properties.
Asphalt Emulsion: a mixture of asphalt particles and an emulsifying agent such
As bentonite clay and water. These components are combined by using a
chemical or a clay emulsifying agent and mixing or blending machinery.
Asphalt Felt: an asphalt-saturated and/or an asphalt-coated felt. (See Felt.).
Asphalt Primer: see Primer.
Asphalt Roof Cement: a trowelable mixture of solvent-based bitumen, mineral
stabilizers, other fibers and/or fillers. Classified by ASTM Standard D 2822-91
Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos-Free,
Types I and 11. Type I is generally referred to as "plastic cement," and is made
from asphalt characterized as self-sealing, adhesive and ductile, and conforming
to ASTM Specification D 312, Type l; Specification D 449,
Types I or Il; or Specification D 946. (See Plastic Cement and Flashing Cement.)
Type II is generally referred to as "vertical-grade flashing cement," and is
made from asphalt characterized by a high softening point and relatively
low ductility, and conforming to the requirement of ASTM Specification D
312, Types II or lil; or Specification D 449, Type lilt (See Plastic Cement
and Flashing Cement.).
Asphaltene: a high molecular weight hydrocarbon fraction precipitated from
asphalt by a designated solvent (paraffinic naphtha) at a specified temperature
and solvent-asphalt ratio.
ASTM: American Society for Testing and Materials.
Aggregate: The standard term for any granular mineral material used for
surfacing a built-up roof – crushed stone, crushed slag or water worn gravel.
Asphalt:A brownish-black solid or semisolid mixture of bitumens obtained from
native deposits or as a petroleum byproduct, used in paving, roofing and
waterproofing. Often applied to various papers, felts, and sealant products for
waterproofing.
Back-Nailing: (also referred to as Blind-Nailing) the practice of nailing the back
portion of a roofing ply, steep roofing unit, or other components in a manner so
that the fasteners are covered by the next sequential ply, or course, and are not
exposed to the weather in the finished roof system.
Back-Surfacing: fine mineral matter applied to the back side of asphalt shingles
and roll roofing to keep them from sticking together while packaged.
Ballast: an anchoring material, such as aggregate, or precast concrete pavers,
which employ the force of gravity to hold (or assist in holding) single-ply roof
membranes in place.
Bar Joist: see Steel Joist.
Barrel Vault: a building profile featuring a rounded profile to the roof on the short
axis, but with no angle change on a cut along the long axis.
Base Flashing (membrane base flashing): plies or strips of roof membrane
material used to close-off and/or seal a roof at the roof-to-vertical intersections,
such as at a roof-to-wall juncture. Membrane base flashing covers the edge of
the field membrane. (Also see Flashing.).
Base Ply: the lowermost ply of roofing in a roof membrane or roof system.
Base Sheet: an impregnated, saturated, or coated felt placed as the first ply in
some multi-ply built-up and modified bitumen roof membranes.
Batten: (1) cap or cover; (2) in a metal roof: a metal closure set over, or covering
the joint between, adjacent metal panels; (3) wood: a strip of wood usually set in
or over the structural deck, used to elevate and/or attach a primary roof covering
such as tile; (4) in a membrane roof system: a narrow plastic, wood, or metal bar
which is used to fasten or hold the roof membrane and/or base flashing in place.
Batten Seam: a metal panel profile attached to and formed around a beveled
wood or metal batten.
Bitumen: (1) a class of amorphous, black or dark colored, (solid, semi-solid, or
viscous) cementitious substances, natural or manufactured, composed principally
of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in
petroleum asphalts, coal tars and pitches, wood tars and asphalts; (2) a generic
term used to denote any material composed principally of bitumen, typically
asphalt or coal tar.
Bitumen-Stop: see Envelope and Bleed Sheet.
Bituminous Emulsion: a suspension of minute particles of bituminous material
in water or other aqueous solution. (See Asphalt Emulsion.)
Blackberry (sometimes referred to as Blueberry or Tar-Boil): a small bubble
or blister in the flood coating of an aggregate-surfaced built-up roof membrane.
Blanket (Bats) Insulation: fiberglass or other compressible fibrous insulation,
generally available in roll form.
Bleed-Sheet: a sheet material used to prevent the migration of bitumen.
Bleeder Strip: see Rake-Starter.
Blind-Nailing: the use of nails that are not exposed to the weather in the finished
roofing system.
Blister: an enclosed pocket of air, which may be mixed with water or solvent
vapor, trapped between impermeable layers of felt or membrane, or between the
membrane and substrate.
Blocking: sections of wood (which may be preservative treated) built into a roof
assembly, usually attached above the deck and below the membrane or flashing,
used to stiffen the deck around an opening, act as a stop for insulation, support a
curb, or to serve as a nailer for attachment of the membrane and/or flashing.
Blowing Agent: an expanding agent used to produce a gas by chemical or
thermal action, or both, in manufacture of hollow or cellular materials.
BOCA: Building Officials and Code Administrators, International, Inc. (author of
the BOCA National Building Code).
BOMA: Building Owners & Managers Association, International.
Bond: the adhesive and/or cohesive forces holding two components in positive
contact.
Bond, Chemical: adhesion between surfaces, usually of similar materials,
resulting from a chemical reaction or cross-linking of polymer chains.


Bond, Mechanical: adhesion between surfaces resulting from interracial forces
or a physical interlocking.
Bonding Agent: a chemical substance applied to a suitable substrate to create
bond between it and a succeeding layer.
Boot: (1) a covering made of flexible material, which may be preformed to a
particular shape, used to exclude dust, dirt, moisture, etc. from around a
penetration; (2) a flexible material used to form a closure, sometimes installed at
inside and outside corners.
Brake: hand- or power-activated machinery used to form metal.
Bridging: (1) when the membrane is unsupported at a juncture; (2) bridging in
steep-slope roofing is a method of reroofing over standard-sized asphalt shingles
with metric-sized asphalt shingles.
British Thermal Unit (BTU): the heat energy required to raise the temperature of
one pound of water one degree Fahrenheit (joule).
Brooming: an action carried out to facilitate embedment of a ply of roofing
material into hot bitumen by using a broom, squeegee, or special implement to
smooth out the ply and ensure contact with the bitumen or adhesive under the
ply.
Buckle: an upward, elongated tenting displacement of a roof membrane
frequently occurring over insulation or deck joints. A buckle may be an indication
of movement within the roof assembly.
Building Code: published regulations and ordinances established by a
recognized agency prescribing design loads, procedures, and construction
details for structures. Usually applying to designated jurisdictions (city, county,
state, etc.). Building codes control design, construction, and quality of materials,
use and occupancy, location and maintenance of buildings and structures within
the area for which the code has been adopted.
Built-Up Roof Membrane (BUR): a continuous, semi-flexible multi-ply roof
membrane, consisting of plies or layers of saturated felts, coated felts, fabrics, or
mats between which alternate layers of bitumen are applied. Generally, built-up
roof membranes are surfaced with mineral aggregate and bitumen, a
liquidapplied coating, or a granule-surfaced cap sheet.
Bundle: an individual package of shakes or shingles.
Bush Hammer: a hammer, originally a hand tool but now usually power driven,
having a serrated face containing many pyramid-shaped points; used to provide
a roughened surface on concrete.
Butt Joint: a joint formed by adjacent, separate sections of material, such as
where two neighboring pieces of insulation abut.
Button Punch: a process of indenting two or more thicknesses of metal that are
pressed against each other to prevent slippage between the metal.
Butyl: rubber-like material produced by copolymerizing isobutylene with a small
amount of isoprene. Butyl may be manufactured in sheets, or blended with other
elastomeric materials to make sealants and adhesives.
Butyl Coating: an elastomeric coating system derived from polymerized
isobutylene. Butyl coatings are characterized by low water vapor permeability.


Butyl Rubber: a synthetic elastomeric based on isobutylene and a minor amount
of isoprene. It is vulcanizable and features low permeability to gases and water
vapor.
Butyl Tape: a sealant tape sometimes used between metal roof panel seams
and end laps; also used to seal other types of sheet metal joints, and in various
sealant applications.
Bitumen: Any of various flammable mixtures of hydrocarbons and other
substances, occurring naturally or obtained by distillation from coal or petroleum,
which are a component of asphalt and tar and are used for waterproofing. Found
in petroleum asphalts, coal tars and pitches, wood tars and asphalts.
Built-up Roof Membrane (BUR): A continuous, semi-flexible, multi-ply roof
membrane, consisting of layers of felt, fabrics or mats.
Cant: a beveling of foam at a right angle joint for strength and water run off.
Cant Strip: a beveled or triangular-shaped strip of wood, wood fiber, perlite, or
other material designed to serve as a gradual transitional plane between the
horizontal surface of a roof deck or rigid insulation and a vertical surface.
Cap Flashing: usually composed of metal, used to cover or shield the upper
edges of the membrane base flashing, wall flashing, or primary flashing. (See
Flashing and Coping.)
Cap Sheet: a granule-surface coated sheet used as the top ply of some built-up
or modified bitumen roof membranes and/or flashing.
Capacitance Meter: a device used to locate moisture or wet materials within a
roof system by measuring the ratio of the change to the potential difference
between two conducting elements separated by a nonconductor.
Capillary Action: the action that causes movement of liquids by surface tension
when in contact with two adjacent surfaces such as panel side laps.
Catalyst: an ingredient in a coating of SPF which initiates a chemical reaction or
increases the rate of a chemical reaction.
Cathodic: with regard to metal and galvanic response, Cathodic metals are
lower in the galvanic series. (May be protected by the more anodic metals.).
Caulk: a material (usually a composition of vehicle and pigment) used for
filling/sealing joints or junctures, where no elastomeric properties are required.
(See Sealant.).
Caulking: (1) the physical process of sealing a joint or juncture; (2) sealing and
making weather-tight the joints, seams, or voids between adjacent units by filling
with a sealant.
Cavitation: the vaporization of a liquid under the suction force of a pump, usually
due to inadequate flow to a pump. The vaporization can create voids within the
pump supply line. In SPF spray pumps, cavitation will result in off-ration foam.
Cavity Wall: a wall built or arranged to provide an air space within the wall (with
or without insulating material), in which the inner and outer materials are tied
together by structural framing.
CCF: 100 cubic feet.
C-Channel: a structural framing member.
Cementitious Waterproofing: heavy cement-based compounds and various
additives that are mixed and packaged for use in a dry form; the packaged
mixture is then mixed with water and liquid bonding agents to a workable
concrete-like consistency.
Centipoise: a unit of measure of absolute viscosity. (Note: The viscosity of water
is one centipoise. The lower the number, the less the viscosity.).
Centistoke: a unit of viscosity—the ratio of a liquid's absolute viscosity to the
density of that liquid.
CERL: Construction Engineering Research Laboratory.
Chalk: a powdery residue on the surface of a material.
Chalk Line: a line made on the roof by snapping a taut string or cord dusted with
colored chalk. Used for alignment purposes.
Chalking: the degradation or migration of an ingredient, in paints, coatings, or
other materials.
Channel Flashing: For steep-slope roof construction) a type of flashing used at
roof-to-wall junctures and other roof-to-vertical plane intersections where an
internal gutter is needed to handle runoff. Commonly used with profile tile.
Chemical Resistance: the ability to withstand contact with specified chemicals
without a significant change in properties.
Chevron: a style of metal panel seaming/design.
Chimney: stone, masonry, prefabricated metal, or a wood framed structure,
containing one or more flues, projecting through and above the roof.
Chlorinated Polyethylene (CPE): a thermoplastic material, used for single-ply
roof membranes, composed of high molecular weight polyethylene which has
been chlorinated—a process that yields a flexible rubber-like material.
Chlorosulfonated Polyethylene (CSPE or CSM): (probably best known by the
DuPont trade name Hypalon™) a synthetic, rubber-like thermoses material,
based on high molecular weight polyethylene with suphonyl chloride, usually
formulated to produce a self-vulcanizing membrane. Classified by ASTM
Standard D 501 9-89.
Cladding: a material used as the exterior wall enclosure of a building.
Cleat: a metal strip, plate or metal angle piece, either continuous or individual
("clip"), used to secure two or more components together.
Clerestory: an upward extension of enclosed space created by carrying a
setback vertical, wall (typically glazed) up and through the roof slope. Two
intersecting shed roofs on different planes. (See Figure 1.).
Clip: an individual (discrete) cleat. (See Cleat.).
Clipped Glable: a gable cutback at the peak in a hip-roof form. (See Figure 2.).
Closed-Cut Valley: a method of valley application in which shingles from one
side of the valley extend across the valley while shingles from the other side are
trimmed back approximately 2 inches (51 mm) from the valley centerline.
Closure Strip: a metal or resilient strip, such as neoprene foam, used to close
openings created by joining metal panels or sheets and flashings.
Coal Tar: a dark brown to black colored, semi-solid hydrocarbon obtained as
residue from the partial evaporation or distillation of coal tars. Coal tar pitch is
further refined to conform to the following roofing grade specifications:
Coal Tar Bitumen: a proprietary trade name for Type lil coal tar used as
the dampproofing or waterproofing agent in dead-level or low-slope builtup
roof membranes, conforming to ASTM D 450, Type lilt.
Coal Tar Pitch: a coal tar used as the waterproofing agent in dead-level
or low-slope built-up roof membranes, conforming to ASTM Specification
D 450, Type I or Type lilt.
Coal Tar Waterproofing Pitch: a coal tar used as the dampproofing or
waterproofing agent in belowgrade structures, conforming to ASTM
Specification D 450, Type II.
Coal Tar Felt: a felt that has been saturated with refined coal tar.
Coal Tar Roof Cement: a trowelable mixture of processed coal tar base,
solvents, mineral fillers and/or fibers. Classified by ASTM Standard D 4022 Coal
Tar Roof Cement.
Coarse Orange Peel Surface Texture: a surface showing a texture where
nodules and valleys are approximately the same size and shape. This surface is
acceptable for receiving a protective coating because of the roundness of the
nodules and valleys. The theoretical covering rate cannot be used without adding
a minimum of 25% additional material.
Coated Base Sheet: a felt that has previously been saturated Hilled or
impregnated) with asphalt and later coated with harder, more viscous asphalt,
which greatly increases its impermeability to moisture.
Coated Fabric: fabrics that have been impregnated and/or coated with a
Plasticlike material in the form of a solution, dispersion hot-melt, or powder. The
term also applies to materials resulting from the application of a preformed film to
a fabric by means of calendering.
Coated Felt (Sheet): (1) an asphalt-saturated felt that has also been coated on
both sides with harder, more viscous "coating" asphalt; (2) a glass fiber felt that
has been simultaneously impregnated and coated with asphalt on both sides.
Coating: a layer of material spread over a surface for protection or decoration.
Coatings for SPF are generally liquids, semi-liquids, or mastics; spray, roller, or
brush applied; and cured to an elastomeric consistency.
Cobwebbing: a phenomenon observed during spray application characterized
by the formation of web-like threads along with the usual droplets leaving the
spray gun nozzle.
Coefficient of Thermal Expansion: a mathematical formulation used to predict
the change in dimension (typically length) of a material as a function of
temperature change.
Cohesion: the degree of internal bonding of one substance to itself.
Coil Coating: the application of a finish to a coil of metal using a continuous
mechanical coating process.
Cold Flow: relatively slow deformation of a material at or below room
temperature. (See Creep).
Cold Forming: the process of using press brakes, roll farmers, etc., to shape
metal into desired profiles at ambient room temperature.
Cold Process Built-Up Roof: a continuous, semi-flexible roof membrane,
consisting of a ply or plies of felts, mats or other reinforcement fabrics that are
laminated together with alternate layers of liquid-applied (usually asphalt-solvent
based) roof cements or adhesives installed at ambient or a slightly elevated
temperature.
Cold Rolled: the process of forming steel into sheets, panels, or shapes on a
series of rollers at ambient room temperatures.
Collector Box: see Conductor Head.
Color Stability: the ability of a material to retain its original color.
Column: a primary structural member used in a vertical position in a building to
transfer loads from horizontal structural members (e.g., main roof beams,
trusses, or rafters) to the foundation/footing.
Combing Ridge: a term used to describe an installation of finishing slate at the
ridge of a roof whereby the slates on one side project beyond to the apex of the
ridge.
Combustible: capable of burning.
Compatible Materials: two or more substances that can be mixed, blended, or
attached without separating, reacting, or affecting the materials adversely.
Composition Shingle: a unit of asphalt shingle roofing.
Compounded Thermoplastics: a category of roofing membranes made by
blending thermoplastic resins with plasticizers, various modifiers, stabilizers,
flame retardants, UV absorbers, fungicides, and other proprietary substances,
alloyed with proprietary organic polymers. Some of the membranes listed in this
generic category are CPA, EIP, NBP, and TPA.
Compressive Strength: the ability of materials and components to resist
deformation or other damage caused by the weight of compression of either live
or dead loads.
Concealed-Nail Method: a method of asphalt roll roofing application in which all
nails are driven into the underlying course of roofing and covered by an adhered,
overlapping course.
Condensate: the liquid resulting from the condensation of a gas or vapor.
Condensation: the conversion of water vapor or other gas to liquid state as the
temperature drops or atmospheric pressure rises. (Also see Dew Point.).
Conditioning: the exposure of a material to the influence of a prescribed
atmosphere for a stipulated period of time or until a stipulated relation is reached
between material and atmosphere.
Conductance, Thermal: the thermal transmission in unit time through unit area
of a particular body or assembly having defined surfaces, when unit average
temperature difference is established between the surfaces. C=Btu/h~ft2~°F.
Conductor Head: a transition component between a through-wall scupper and
downspout to collect and direct run-off water.
Construction Joint: a formed or assembled joint at a predetermined location
where two successive placements of concrete meet.
Contact Cements: adhesives used to adhere or bond various roofing
components. These adhesives adhere mated components immediately on
contact of surfaces to which the adhesive has been applied.
Contamination: the process of making a material or surface unclean or unsuited
for its intended purpose, usually by the addition or attachment of undesirable
foreign substances.
Coping: the covering piece on top of a wall which is exposed to the weather,
usually made of metal, masonry, or stone. It is preferably sloped to shed water
back onto the roof.
Copolymer: the product of polymerization of two or more substances at the
same time; a "mixed" polymer.
Copolymerization: a chemical reaction that results in the bonding of two or
more dissimilar monomers to produce large, long-chain molecules which are
copolymers.
Copper: a natural weathering metal used in metal roofing; typically used in 16 or
20 ounce per square foot thickness (4.87 or 6.10 kg/sq m).
Cornice: the decorative horizontal molding or projected roof overhang.
Counter Batten: vertical wood strips installed on sloped roofs over which
horizontal battens are secured. The primary roof covering is attached or secured
to these horizontal battens.
Counterflashing: formed metal sheeting secured on or into a wall, curb, pipe,
rooftop unit, or other surface, to cover and protect the upper edge of the
membrane base flashing or underlying metal flashing and associated fasteners
from exposure to the weather.
Course: (1) the term used for each row of shingles of roofing material that forms
the roofing, waterproofing, or flashing system; (2) one layer of a series of
materials applied to a surface (e.g., a five-course wall flashing is composed of
three applications of roof cement with one ply of felt or fabric sandwiched
between each layer of roof cement.).
Cove: see Fillet.
Cover Plate: a metal strip sometimes installed over the joint between formed
metal pieces.
Coverage: the surface area covered by a specific quantity of a particular
material.
CPA: Copolymer Alloy.
CPE: Chlorinated Polyethylene.
Crack: a non-linear separation or fracture occurring in a material. May be
generally caused by induced stress, dimensional instability, or substrate
movement. Some cracks may be more of a linear separation or fracture. (See
Split.).
Cream Time: time in seconds (at a given temperature) when the A and B
components will begin to expand after being mixed.
Creep: the permanent deformation of a roofing material or roof system caused by
movement of the roof membrane, or compression of a roof insulation board at
fastener positions, that results from continuous load or thermal stress or loading.
Creep at roof temperature is sometimes called "cold flow."
Cricket: an elevated roof substrate or structure, constructed to divert water
around a chimney, curb, away from a wall, expansion joint, or other
projection/penetration. (See Saddle.).
Cross-Linking: the formation of chemical bonds between polymeric chains to
yield an insoluble, three dimensional polymeric structure. Cross-linking of rubber
is referred to as vulcanization or "curing."
Cross Ventilation: the effect that is provided when air moves through a roof
cavity between the vents.
CRREL: Cold Regions Research and Engineering Laboratory.
Crystalline Waterproofing: a compound of cement, quartz or silica sand, and
other active chemicals that are mixed and packaged for use in a dry powder
form; the packaged mixture is then mixed with water and applied to a concrete
surface where it penetrates into the pores of concrete.
CSI: Construction Specifications Institute.
CSM: ASTM designation for chlorosulfonated polyethylene. (See CSPE.).
CSPE: chlorosulfonated polyethylene.
Cupola: a relatively small roofed structure, generally set on the ridge or peak of
a main roof area. (See Figure 3.)
Curb: (1) a raised member used to support roof penetrations, such as skylights,
mechanical equipment, hatches, etc. above the level of the roof surface; (2) a
raised roof perimeter relatively low in height.
Cure: a process whereby a material is caused to form permanent molecular
linkages by exposure to chemicals, heat, pressure, and/or weathering.
Cure Time: the time required to effect curing. The time required for a material to
reach its desirable long-term physical characteristics.
Cured Concrete: concrete that has attained its intended design performance
properties.
Curing Agent: an additive in a coating or adhesive that results in increased
chemical activity between the components with an increase or decrease in rate of
cure.
Curing Compound: a liquid that is sprayed or otherwise applied to newly placed
concrete which retards the loss of water during curing.
Cutback: solvent-thinned bitumen used in cold-applied ("process") roofing
adhesives, roof cements, and roof coatings.
Cutoff: Permanent details designed to seal and prevent lateral water movement
in an insulation system, and used to isolate sections of a roofing system. (Note: A
cutoff is different from a tie-off, which may be a temporary or permanent seal.)
(See Tie-Off.).
Cutout: the open portions of a strip shingle between the tabs. (See Figure 4.).
Catalyst: A substance, usually used in small amounts relative to the reactants,
that modifies and increases the rate of a reaction without being consumed in the
process.
Contract: The written form of an agreement, enforceable by law, between two or
more people.
Contractor :A trained professional who agrees to furnish materials or perform
services at a specified price. *Only hire contractors who carry contractors’
licenses.
Cure :To prepare, preserve or finish (a substance) by a chemical or physical
process, including heat, pressure and weathering.
Dampproofing: treatment of a surface or structure to resist the passage of water
in the absence of hydrostatic pressure.


Dead Level: essentially horizontal or flat, as in a roof deck or rooftop with no
intentional slope to the roof drains. Also referred to as zero (0) slope. (See
Slope.).
Dead-Level Asphalt: see Asphalt.
Dead Loads: permanent non-moving loads that result from the weight of a
building's structural and architectural components, mechanical and electrical
equipment, and the roof assembly itself. Essentially the same as "dead weight"
or "dead weight loads."
Deck: a structural component of the roof of a building. The deck must be capable
of safely supporting the design dead and live loads, including the weight of the
roof systems, and the additional live loads required by the governing building
codes. Decks are either non-combustible (e.g., corrugated metal, concrete, or
gypsum) or combustible (e.g., wood plank or plywood), and provide the substrate
to which the roofing or waterproofing system is applied.
Deflection (Bowing, Sagging): the downward displacement of a structural
member or system under load.
Degradation: a deleterious change in the chemical structure, physical
properties, or appearance of a material due to natural or artificial exposure (e.g.,
exposure to radiation, moisture, heat, freezing, wind, ozone, oxygen, etc.).
Degree Days: the difference between a reference temperature (usually 65°F [1
8.3°C]) and the mean temperature for the day, times 24 hours, times the number
of days in the period. Degree days are used to compare the severity of cold or
heat during the heating or cooling season.
Delamination: separation of the laminated layers of a component or system.
Design Loads: those loads specified in building codes or standards published by
federal, state, county, or city agencies, or in owners' specifications to be used in
the design of a building.
Dew Point Temperature: the temperature at which water vapor condenses in
cooling air at the existing atmospheric pressure and vapor content. Cooling at or
below the dew point will cause condensation.
Diaphragm: see Roof Diaphragm.
Diffusion: the movement of water vapor from regions of high concentration (high
water vapor pressure) toward regions of lower.
Dimensional Shingle: a shingle that is textured, overlayed, or laminated and
designed to produce a three-dimensional effect. (Also see Laminated Shingles
and Architectural Shingles).
Dimensional Stability: the ability of a material to resist change in length, width,
and/or thickness that results from exposure to elevated or freezing temperatures,
and moisture, over time.
DOE: Department of Energy.
Dome: a roof that is shaped like a half-circle, or a variation of one.
Domer: a framed projection through the slopping plane of a roof. (See figure 5).
Double Coverage: application of asphalt, slate, or wood roofing such that the
lapped portion is at least 2 inches (51mm) wider than the exposed portion,
resulting in two layers of roofing material over the deck.


Double Graveling: the process of applying two layers or flood coats of bitumen
and aggregate to a built-up roof. Loose aggregate should be swept from the first
application prior to the second coating of bitumen and aggregate. Approximately
50% of the second aggregate application will remain adhered in the bitumen
flood coat unless physically removed.
Double Lock Standing Seam: a standing seam that utilizes a double,
overlapping interlock between two seam panels. (See Standing Seam.).
Downspout: a conduit used to carry runoff water from a scupper, conductor
head, or gutter of a building to a lower roof level, or to the ground or storm water
runoff system.
Drain: an outlet or other device used to collect and direct the flow of runoff water
from a roof area.
Drip Edge: a metal flashing, or other overchanging component, with an outward
projecting lower edge, intended to control the direction of dripping water and help
protect underlying building components. A drip edge also can be used to break
the continuity of contact between the roof perimeter and wall components to help
prevent capillary action.
Dry: (1) to change the physical state of a material by the loss of components
through evaporation, absorption, oxidation, or a combination of these effects; (2)
the absence of water or moisture.
Dry Bulb Temperature: the temperature of air as measured by an ordinary
thermometer. Units are F (C).
Dry Film Thickness: the thickness, expressed in mils, of an applied and cured
coating or mastic. For comparison, seeWet Film Thickness.
Dry-In or Dry-In Felt: usually the underlayment or the process of applying the
underlayment for steep roofing.
Drying Time: the time required for the loss of volatile components so that the
material will no longer be adversely affected by weather conditions such as dew,
rain, or freezing.
Dual Level Drain: in waterproofing, an outlet or other device with provisions for
drainage at both the wearing surface level and the waterproofing membrane level
used to collect and direct the flow of runoff water from a horizontal slip. (See
NRCA Waterproofing Detail WP-9.).
Durability: the ability to withstand physical, chemical, or environmental abuse.
Dust Free: a surface is considered dust free when a finger can be lightly run
over the surface without picking up any dirt, dust, or chalk on the finger.
Dynamic Load: any load which is nonstatic, such as a wind load or a moving live
load.
Dry Rot :A fungous disease that causes timber to become brittle and crumble
into powder.
Elastomeric Top Coat:A high-performance 100% acrylic foam roof coating that
eliminates UV attack. The coating must be applied within 72 hours after
application of the foam roofing insulation .
Eave: a projecting edge of a roof that extends beyond the supporting wall. (See
Figure 6.).
Eave Height: the vertical dimension from finished grade to the cave.


Eaves-Trough: see Gutter.
ECH: polyepichlorohydrin, commonly referred to as epichlorohydrin. (See
Epichlorohydrin.).
Edge Stripping: membrane flashing strips cut to specific widths used to
seal/flash perimeter edge metal and the roof membrane.
Edge Venting: the practice of providing regularly spaced or continuously
protected (e.g., louvered) openings along a roof edge or perimeter, used as part
of a ventilation system to dissipate heat and moisture vapor.
Efflorescence: the formulation of crystalline deposits, generally whitish in color,
on the surface of stone, brick, concrete, or other masonry surface when moisture
moves through and evaporates on the masonry. May also be caused by free
alkalies leached from mortar, grout, or adjacent concrete.
EIP: Ethylene Interpolymer.
Elasticity: the property of matter by virtue of which it tends to return to its original
size and shape after removal of a stress or force which caused a deformation.
Elastomer: natural or synthetic material which, at room temperature, can be
stretched under low stress and, upon immediate release of the stress or force,
will return quickly to its approximate original dimensions.
Elastomeric: the elastic, rubber-like properties of a material that will stretch
when pulled and will return relatively quickly to its original shape when released.
Elastomeric Coating: a coating system which, when fully cured, is capable of
being stretched at least twice its original length (100% elongation) and recovering
to its original dimensions.
Electrolyte: a liquid, most often a solution, that will conduct current.
Elongation: the ability of a material (e.g., roofing membrane) to be stretched by
the application of a force.
Embedment: (1) the process of installing or pressing-in a reinforcement felt,
fabric, mat or panel uniformly into bitumen or adhesive; (2) the process of
pressing granules into coating during the manufacture of factory-prepared
roofing; (3) the process whereby ply sheet, aggregate, or other roofing
components settle into hot- or cold-applied bitumen via the force of gravity.
Embrittlement: the loss of flexibility or elasticity of a material. The transition of a
flexible material to a brittle state.
Emulsion: a dispersion of fine particles or globules in a liquid. (See Asphalt
Emulsion and Bitumen Emulsion.)
End Lap: the distance of overlap where one ply, panel, or piece extends beyond
the end of the immediately adjacent underlying ply, panel, or piece.
Envelope (Bitumen-Stop): a continuous edge seal formed at the perimeter and
at penetrations by extending the base sheet or one ply of felt beyond the edge of
the membrane field plies. After all overlying field plies or insulation are in place,
the extended ply is turned back onto the membrane and adhered. The envelope
is intended to prevent bitumen seepage from the edge of the membrane.
EPDM: Ethylene Propylene Diene Monomer (See also Ethylene Propylene Diene
Terpolymer.)
Epichlorohydrin (ECH): a synthetic rubber including two epichlorohydrin based
elastomers. It is similar to and compatible with EPDM. ECH is typically used in
lieu of EPDM when enhanced resistance to animal fat or other oils is needed.
Epoxy: a class of synthetic, thermosetting resins that produce tough, hard,
chemical-resistant coatings and adhesives.
Equilibrium Moisture Content (EMC): (1) the moisture content of a material
stabilized at a given temperature and relative humidity, expressed as percent
moisture by weight; (2) the typical moisture content of a material in any given
geographical area.
Equiviscous Temperature (EVT): the temperature at which a bitumen attains
the proper viscosity for built-up membrane application.
Equiviscous Temperature (EVT) Application Range: the recommended
bitumen application temperature range. The range is approximately 25°F (1 4°C)
above or below the EVT, thus giving a range of approximately 50°F (28°C). The
EVT Range Temperature is measured in the mop car t or mechanical spreader
just prior to application of the bitumen to the substrate.
Equiviscous Temperature (EVT) for Asphalt: the recommended EVT for
roofing asphalt (ASTM D312, Type I, 11, 111, or IV) is as follows:
Mop Application: the temperature at which the asphalt's apparent viscosity
is 125 centipoise (0.125 Pass).
Mechanical Spreader Application: the temperature at which the asphalt's
apparent viscosity is 75 centipoise (0.075 Pans).
Note: If there are simultaneous mop and mechanical spreader applications, in
order to avoid the use of two kettles, the EVE for mechanical spreader
application may be used for both application techniques.
Equiviscous Temperature (EVA) for Coal Tar: the recommended EVT for
roofing coal tar (ASTM D 450, Type I or lil) is the temperature at which the coal
tar's apparent viscosity is 25 centipoise (0.025 Pans).
Ethylene Interpolymers (EIP): a group of thermoplastic compounds generally
based on PVC polymers from which certain single-ply roofing membranes can be
formulated.
Ethylene Propylene Diene Terpolymer (EPDM): designated nomenclature of
ASTM for a terpolymer of ethylene, propylene, and a diene. EPDM material is a
thermosetting synthetic elastomer.
EVT: Equiviscous Temperature.
Exhaust Ventilation: air that is typically vented or exhausted from the roof
cavity, typically through vents installed on the upslope portion of the roof. For
example, with most steep-slope roof assemblies exhaust vents are typically
located at or near the ridge.
Exotherm: heat generated by a chemical reaction.
Expansion Cleat: a cleat designed to handle thermal movement of the metal
roof panels.
Expansion Joint: a structural separation between two building elements that
allows free movement between the elements without damage to the roofing or
waterproofing system.
Exposed-Nail Method: a method of asphalt roll roofing application in which all
nails are driven into the adhered, overlapping course of roofing. Nails are
exposed to the weather.
Exposure: (1) the traverse dimension of a roofing element or component not
overlapped by an adjacent element or component in a roof covering. For
example, the exposure of any ply in a built-up roof membrane may be computed
by dividing the felt width minus 2 inches (51 mm) by the number of shingled plies;
thus, the exposure of 36 inch (91 4mm) wide felt in a shingled, four-ply
membrane should be approximately 84/~ inches (21 6mm) (See Figure 8); (2) the
dimension of sidewall or roofing covering that is not covered or overlapped by the
upslope course of component. The typical exposure for a standard-size, 3-tab
shingle is 5 inches (127mm), depending upon manufacturer specifications. (See
Figure 9.)
Extrusion: a manufacturing process which consists of forcing batched and
formulated material (which may be molten) through an orifice called a "die." The
shape and dimensions of the orifice determine the shape and dimensions of the
finished product. Extrusion is one method by which some single-ply roofing
membranes are manufactured.
Eyebrow: a dormer, usually of small size, whose roof line over the upright face is
typically an arched curve, turning into a reverse curve to meet the horizontal at
either end. Also, a small shed roof projecting from the gable end of the larger,
main roof area.
Fabric: a woven cloth or material of organic or inorganic filaments, threads, or
yarns used for reinforcement in certain membranes and flashings.
Factory Mutual Research Corporation (FMRC): (commonly referred to as
"FM") a research and testing organization that classifies roofing components and
assemblies for their fire, traffic, impact (hail), weathering, and wind-uplift
resistance for four major insurance companies in the United States.
Factory Seam: a splice/seam made by the manufacturer during the assembly of
sections of materials into large sheets.
Fading: any lightening of initial color.
Fallback: a reduction in the softening point temperature of asphalt that occurs
when asphalt is heated for prolonged periods at elevated temperature. (See
Softening Point Drift.)
Fascia: a vertical or steeply sloped roof or trim located at the perimeter of a
building. Typically, it is a border for the low-slope roof system that waterproofs
the interior portions of the building.
Fasteners: any of a wide variety of mechanical securement devices and
assemblies, including nails, screws, cleats, clips, and bolts, which may be used
to secure various components of a roof assembly.
Feathering Strips: tapered wood filler strips placed along the butt ends of old
wood shingles to create a relatively smooth surface when reroofing over existing
wood shingle roofs. Referred to in some regions of the country as "horse
feathers" or leveling strips.
Felt: a flexible sheet manufactured by the interlocking of fibers through a
combination of mechanical work, moisture, and heat. Roofing felts may be
manufactured principally from wood pulp and vegetable fibers (organic felts),
asbestos fibers (asbestos felts), glass fibers Fiberglass felts or ply sheet), or
polyester fibers.
Felt Machine (Felt Layer): a mechanical device used for applying bitumen and
roofing felt or ply sheet simultaneously.
Ferrule: a small metal sleeve placed inside a gutter at the top. A spike is nailed
through the gutter into the fascia board to hold the gutter in place. The ferrule
acts as a spacer in the gutter to maintain its original shape.
Fiberglass Insulation: blanket or rigid board insulation, composed of glass
fibers bound together with a binder, faced or unfaced, used to insulate roofs and
walls. Rigid boards usually have an asphalt and kraft paper facer.
Field of the Roof: the central or main portion of a roof, excluding the perimeter
and flashing.
Field Seam: a splice or seam made in the field (not factory) where overlapping
sheets are joined together using an adhesive, splicing tape, or heat- or
solventwelding.
Filler: a relatively inert ingredient added to modify physical characteristics.
Fillet: a heavy bead of waterproofing compound or sealant material generally
installed at the point where vertical and horizontal surfaces meet; the desired
effect to take out the 90° angle at the base of a vertical flashing.
Film: a membrane or sheeting having nominal thickness not greater than 10
mils.
Film Thickness: the thickness of a membrane or coating.Wet film thickness is
the thickness of a coating as applied; dry film thickness is the thickness after
curing. Film thickness is usually expressed in mils (thousandths of an inch).
Fin: a term used to describe a deck surface condition. A sharp raised edge
(generally in concrete) capable of damaging a roof membrane or vapor retarder.
Fine Mineral-Surfacing: water-insoluble, inorganic material, more than 50
percent of which passes through a No. 35 sieve. Used on the surface of various
roofing materials and membranes to prevent sticking.
Fire Resistance: the ability of a building component to act as a barrier to the
spread of fire and confine it to the area of origin.
Fishmouth: (also referred to as an EdgeWrinkle) (1) a half-cylindrical or
halfconical
shaped opening or void in a lapped edge or seam, usually caused by
wrinkling or shifting of ply sheets during installation; (2) in shingles, a half-conical
opening formed at a cut edge.
Flaking: detachment of a uniform layer of a coating or surface material, usually
related to internal movement, lack of adhesion, or passage of moisture.
Flame Retardant: a substance which is added to a polymer formulation to
reduce or retard its tendency to burn.
Flame Spread: Per ASTM E 84, a measure of relative combustibility. The flame
spread of a tested material is rated relative to asbestos cement board Flame
spread = 0) and red oak flooring Flame spread = 100).
Flammability: the characteristics of a material to burn or support combustion.
Flange: the projecting edge of a rigid or semi-rigid component, such as a metal
edge flashing flange, skylight flange, flashing boot, structural member, etc.


Flash Point: the lowest temperature of a liquid at which it gives off vapors
sufficient to form an ignitable mixture with air near its surface.
Flashing: components used to weatherproof or seal the roof system edges at
perimeters, penetrations, walls, expansion joints, valley, drains, and other places
where the roof covering is interrupted or terminated. For example, membrane
base flashing covers the edge of the field membrane, and cap flashings or
counterflashings shield the upper edges of the base flashing.
Flashing Cement: as used by the roofing industry, an ASTM D 2822 Type II roof
cement that is a trowelable mixture of solvent-based bitumen and mineral
stabilizers that may include asbestos or other inorganic or organic fibers.
Generally, flashing cement is characterized as vertical-grade, which indicates it is
intended for use on vertical surfaces. (See Asphalt Roof Cement and Plastic
Cement.)
Flashing Collar: (sometimes referred to as a Roof Jack or Flashing Boot) an
accessory flashing used to cover and/or seal soil pipe vents and other
penetrations through the roof.
Flat Lock: a method of interlocking metal panels in which one panel edge is
folded back on top of itself and the other panel is folded under, after which the
two panels are hooked together.
Fleece: mats or felts composed of fibers (usually non-woven polyester fibers),
often used as a membrane backer.
Flood (Pour) Coat: the surfacing layer of bitumen into which surfacing
aggregate is embedded on an aggregate-surfaced built-up roof. A flood coat is
generally thicker and heavier than a glaze coat, and is applied at approximately
45-60 pounds per square (2-3 kilograms per meter).
Flood Test: the procedure where a controlled amount of water is temporarily
retained over a horizontal surface to determine the effectiveness of the
waterproofing.
Fluid-Applied Elastomer: a liquid elastomeric material that cures after
application to form a continuous waterproofing membrane.
FM: see Factory Mutual Research Corporation.
Foam Stop: the roof edge treatment upon which SPF is terminated.
Force: an action that changes or tends to change the state of rest or motion.
FPL: Forest Products Laboratory
Framed Opening: an opening in a wall or roof of a building, surrounded by
structural framing, usually for field installed accessories such as skylights or
ventilators.
Froth Pack: a term used to describe small, disposable aerosol cans that contain
SPF components. Two component packs are available to do small repairs for
sprayed polyurethane foam-based roofs.
Flashing :A self-adhesive, protective system designed for foam roofing systems
to seal edges at walls, expansion joints, drains, gravel stops and other places
where the roofing material is interrupted or terminated.
G-90: a typical coating weight for galvanized metal sheet. Equates to 0.90
ounces (26 g) of zinc per sq. ft., measured on both sides.
Gable: a triangular portion of the endwall of a building directly under the sloping
roof and above the eave line. (See Figure 10.)
Gable-Shaped Roof: a single-ridge roof that terminates at gable end(s). (See
Figure 11.)
Galvalume~: trade name for a coating, used over metal, that is composed of
aluminum zinc for corrosion protection.
Galvanic Action: an electroylic reaction between dissimilar metals in the
presence of an electrolyte.
Galvanize: to coat with zinc.
Galvanized Steel: steel coated with zinc for corrosion resistance.
Gambrel: a roof that has two pitches on each side. (See Figure 12.)
Gauge: a measurement of rating metal thickness.
Geocomposite: a prefabricated drainage material used to relieve hydrostatic
pressure against waterproofing and to promote drainage.
Geodesic Dome: a rounded structure made of short, straight, triangular sections
that form polygons. (See Figure 13.)
Geotextile: a tightly woven fabric used to restrict the flow of fine soil particles
and other contaminants while allowing water to pass freely through; used for
protection of drainage systems from clogging.
Girt: a horizontal beam that supports wall cladding between columns.
Glass Felt: a sheet composed of bonded glass fibers, suitable for impregnation
and coating in the manufacture of bituminous roofing and waterproofing
materials, and shingles.
Glass Mat: a thin mat composed of glass fibers, woven or non-woven, with or
without a binder. This mat may serve as reinforcement for certain roof materials
and membranes.
Glaze Coat: (1) the top layer of asphalt on a smooth-surfaced built-up roof
membrane; (2) a thin protective coating of bitumen applied to the lower plies or
top ply of a built- up roof membrane when application of additional felts or the
flood coat and aggregate surfacing are delayed. (Also see Flood Coat.)
Gloss: the shine, sheen, or luster of a dried film.
Grain: a unit used to measure the mass of moisture.
Granule: (also referred to as Mineral or Ceramic Granule) opaque, natural, or
synthetically colored aggregate commonly used to surface cap sheets, shingles,
and other granule-surfaced roof coverings.
Gravel: aggregate resulting from the natural erosion of rock.
Gravel Stop: a low profile upward-projecting metal edge flashing with a flange
along the roof side, usually formed from sheet or extruded metal. Installed along
the perimeter of a roof to provide a continuous finished edge for roofing material.
Acts as a bitumen-stop during mop application of hot bitumen along a perimeter
edge.
Groundwater Level: at a particular site, the level below which the subsoil and
rock masses of the earth are fully saturated with water.
Grout: a mixture of cement, sand, and water used to fill cracks and cavities in
masonry.
Grout (Non-Shrink): a cementitious material used to fill pitch-pans/pockets, prior
to the application of a pourable sealer.
Gutter: a channeled component installed along the downslope perimeter of a
roof to convey runoff water from the roof to the drain leaders or downspouts.
Granule: This opaque, natural or synthetically colored aggregate is used for
foam roofing systems as a final protective coating.
Gravel : A natural material applied to tar and gravel roofs. This coarse, granular
aggregate contains small pieces approximately 5/8 inch to 1/2 inch in size.
Heat Aging: controlled exposure of materials to elevated temperatures over
time.
Heat Seaming: the process of joining thermoplastic films, membranes, or sheets
by heating and then applying pressure to bring both materials in contact with
each other. (See HeatWelding.)
Heat Transfer: the transmission of thermal energy from a location of higher
temperature to a location of lower temperature. This can occur by conduction,
convection, or radiation.
Heat Welding: method of melting and fusing together the overlapping edges of
separate sheets or sections of polymer modified bitumen, thermoplastics or some
uncured thermoses roofing membranes by the application of heat (in the form of
hot air or open flame) and pressure. (See Heat Seaming.)
Hem: the edge created by folding metal back on itself.
Hip: the inclined external angle formed by the intersection of two sloping roof
planes. (See Figure 16.)
Hip Roof: a roof that rises by inclined planes to form one or more hips. (See
Figure 17.)
Hoist: a mechanical lifting device.
Holiday: an area where a liquid-applied material is missing or absent.
Honeycomb: voids left in concrete owing to failure of the mortar to fill effectively
the spaces among coarse aggregate particles.
"Hot" or "Hot Stuff": the roofer's term for hot bitumen.
Humidity: the amount of moisture contained in the atmosphere. Generally
expressed as percent relative humidity (the ratio of the amount of moisture [water
vapor] actually present in the air, compared to the maximum amount that the air
could contain at the same temperature.)
HVAC: heating, ventilating, and air conditioning equipment.
Hydration: the chemical reaction by which a substance (such as Portland
cement) combines with water, giving off heat to form a crystalline structure in its
setting and hardening.
Hydrocarbon: an organic chemical compound primarily containing the elements
carbon and hydrogen
Hydrostatic Pressure: the pressure equivalent to that exerted on a surface by a
column of water of a given height.
Hydrostatic Pressure Relief System: a system of perimeter and/or under slab
drains used to regulate the hydrostatic pressure in the earth surrounding a
below-grade structure.

Hygroscopic: the property of a material to attract, absorb, and retain
atmospheric moisture.


Hypalon~: a registered trademark of E.l. duPont de Nemours, Inc., for
"chlorosulfonated polyethylene" (CSPE). (See Chlorosulfonated Polyethylene.)
ICBO: International Conference of Building Officials. Author of The Uniform
Building Code.
Ice Dam: a mass of ice formed at the transition from a warm to a cold roof
surface, frequently formed by refreezing meltwater at the overhang of a steep
roof, causing ice and water to back up under roofing materials.
Ignition Temperature: the minimum temperature to which a solid, liquid, or gas
must be heated in order to initiate or cause self-sustained combustion
independent of the heating element.
Impact Resistance: the ability of a roofing material to resist damage (e.g.,
puncturing) from falling objects, application equipment, foot traffic, etc. The
impact resistance of the roofing assembly is a function of all of its components,
not just the membrane itself.
Impregnate: to coat, saturate, and/or surround the fibers of a reinforcing mat or
fabric with an enveloping liquid material, (e.g., bitumen, elastomeric compound,
etc.).
Incline: the slope of a roof expressed either in percent or in the number of
vertical units of rise per horizontal units of run. (See Slope.)
Infrared Thermography: a practice of roof system analysis where an infrared
camera is used to measure the temperature differential of a roof surface to locate
areas of underlying wet or moist insulation. (See Thermal Image.)
Inorganic: any chemical or compound that is derived from minerals, does not
contain carbon, and is not classified as organic; being or composed of materials
other than hydrocarbons and their derivatives; not of plant or animal origin.
Insect Screen: wire mesh used to prevent insects from entering the building
through ventilators, louvers, or other openings.
Insulation: any of a variety of materials designed to reduce the flow of heat,
either from or into a building. (See also Thermal Insulation.)
Intake Ventilation: the fresh air that is drawn into a passive ventilation system
through vents typically installed in the soffit or eave of a roof.
Interlayment: a felt, metal, or membrane sheet material used between courses
of steep-slope roofing to improve the weather- and water-shedding
characteristics of the primary roof covering during times of winddriven rain and
snow. Typically used with wood shakes.
Interlocking Shingles: individual shingles that mechanically attach to each other
to provide wind resistance.
Internal Pressure: pressure inside a building that is a function of ventilating
equipment, wind velocity, and the number and location of openings and air leaks.
Inverted Roof Membrane Assembly (IRMA`): a patented, proprietary variation
of the "Protected Membrane Roof Assembly" in which Styrofoam Brand
Insulation and ballast are placed over the roof membrane. IRMA™ and
Styrofoam are registered trademarks of the Dow Chemical Company.
IRWC: Institute of Roofing andWaterproofing Consultants
ISANTA: International Staple, Nail & Tool Association
Isocyanate: a highly reactive organic chemical containing one or more
isocyanate (-N=C=O) groups. A basic component in SPF based systems and
some polyurethane coating systems
Insulation :The material or substance used to insulate against heat, cold, sound,
etc.
Joist: any of the small timbers, metal or wood beams arranged parallel from wall
to wall to support a floor, ceiling, or roof of a building.
k-Factor: thermal conductivity for a unit thickness of material. Expressed at
Btu~ln/Hr.Ft2~°F. R-value is equal to the thickness of the thermal material
divided by the k-factor (R=x/k where x = thickness).
Kesternich Test: simulates acid rain conditions by subjecting test specimens to
a sulfur dioxide atmosphere as well as condensing moisture for the purpose of
evaluating rust/corrosion characteristics.
Knee Cap: a metal cover trim that fits over a panel rib after it has been cut and
bent.
Laitance: a layer of weak nondurable material containing cement and fines from
aggregates, brought by bleeding water to the top of overwet concrete. Laitance
may be detected by scraping the concrete surface with a putty knife; if a quantity
of loose powdery material is observed or easily removed, excessive laitance may
be considered to be present.
Laminate: to bond two or more layers of a material together to make a finished
product.
Laminated Shingles: see Dimensional Shingles or Architectural Shingles.
Lap: that part of a roofing, waterproofing, or flashing component that overlaps or
covers any portion of the same or another type of adjacent component.
Lap Cement: an asphalt-based roof cement formulated to adhere overlapping
plies or asphalt roll roofing.
Lap Seam: occurs where overlapping materials are seamed, sealed, or
otherwise bonded.
Latex: a colloidal dispersion of a polymer or elastomer in water which coagulates
into a film upon evaporation of the water.
Lead: a soft workable metal used for miscellaneous flashings.
Leader Head: see Conductor Head.
Leeward: the opposite direction from which the wind is blowing. The side
sheltered from the wind.
Life Cycling Costing: a method of economic analysis that takes into account
expected costs over the useful life of an asset.
Lift: the sprayed polyurethane foam that results from a pass. It usually is
associated with a certain pass thickness and has a bottom layer, center mass,
and top skin in its makeup.
Light Reflectance: the percentage of light that is not absorbed by the surface of
a material.
Live Loads: temporary loads that the roof structure must be designed to support,
as required by governing building codes. Live loads are generally moving and/or
dynamic or environmental, (e.g., people, installation equipment, wind, snow, ice
or rain, etc.).
Load Deflection: see Deflection.
Loose-laid Membranes: membranes that are not attached to the substrate
except at the perimeter of the roof and at penetrations. Typically, loose-laid
membranes are held in place with ballast, such as water-worn stone, gravel,
pavers, etc.
Low Temperature Flexibility: the ability of a membrane or other material to
remain flexible (resist cracking when flexed), after it has been cooled to a low
temperature.
Mansard: a decorative steep-sloped roof on the perimeter of a building.
Mansard Roof: a steeper roof that terminates into a flat roof at its high point.
(See Figure 18.)
Masonry: anything constructed of such materials as bricks, stone, concrete
blocks, ceramic blocks, or concrete.
Mastic: see Asphalt Roof Cement.
Mat: a thin layer of woven, non-woven, or knitted fiber that serves as
reinforcement to the material or membrane.
Mat Slab: a concrete slab designed with reinforcement to resist the uplift forces
created by hydrostatic pressure.
Material Safety Data Sheets (MSDS): a written description of the chemicals in a
product, and pertinent other data including such things as safe handling and
emergency procedures. In accordance with OSHA regulations, it is the
manufacturer's responsibility to produce an MSDS and the employer's
responsibility to communicate its contents to employees.
MBDA: formerly Metal Builders Dealers Association, now Systems Builders
Association.
MBMA: Metal Building Manufacturers Association
MCA: Metal Construction Association
Mechanically-Fastened Membranes: generally used to describe membranes
that have been attached at defined intervals to the substrate. Mechanical
fastening may be performed with various fasteners and/or other mechanical
devices, such as plates or battens.
Membrane: a flexible or semi-flexible material, which functions as the
waterproofing component in a roofing or waterproofing assembly, and whose
primary function is the exclusion of water.
Metal Film: a layer of foil made from a single metallic substance, or from an
alloy,
that is laminated to a membrane during manufacture. The metal foil serves as the
weathering surface of the membrane or flashing material.
Metal Flashing: accessory components fabricated from sheet metal and used to
weatherproof terminating roof covering edges. Frequently used as through-wall
flashing, cap flashing (coping), counterflashing, stepflashing, etc. (See Flashing.)
Metallic Waterproofing: a compound modified through the inclusion of one or
more polymers (e.g. atactic polypropylene, styrene butadiene sytrene, etc.); (2)
composite sheets consisting of a polymer modified bitumen often reinforced and
sometimes surfaced with various types of mats, films, foils, and mineral granules.
Meter: unit of length measurement in the metric system, equal to 39.37 inches.
Mica Dust: crystallized complex silicate minerals that are pulverized into dust
form for use as a release agent. (See Talc.)
Microbiological Resistance: the ability of a material to resist attack and
degradation by various air- and soilborne micro-organisms.
Migration: the absorption of oil or vehicle from a compound into an adjacent
porous surface.
Mill: a unit of measure, one mil is equal to 0.001 inches or 25.400 microns, often
used to indicate the thickness of a roofing membrane.
Mildew: a superficial coating or discoloring of an organic material due to fungal
growth, especially under damp conditions.
Millimeter: a unit of measure equal to one thousandth (0.001) of a meter, or
0.03937 inches.
MIMA: Mineral Insulation Manufacturers Association
Mineral Fiber: inorganic fibers of glass, asbestos, or rock (mineral wool).
Mineral Granules: see Granules.
Mineral Stabilizer: a fine, water-insoluble inorganic material, used in a mixture
with solid or semi-solid hit'~minous materials.
Mineral-Surfaced Roofing: roofing materials whose surface or top layer
consists of mineral granules.
Mineral-Surfaced Sheet: a roofing sheet that is coated on one or both sides with
asphalt and surfaced with mineral granules.
Miter: the joint produced by joining two diagonally cut pieces.
Model Codes: a compilation of standards or codes established to provide
uniformity in regulations pertaining to building construction. Examples: ICBO -
International Conference of Building Officials; BOCA - Building Officials and
Code Administrators; SBC - Standard Building Code.
Modified Bitumen: (1) a bitumen modified through the inclusion of one or more
polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2)
composite sheets consisting of a polymer modified bitumen often reinforced and
sometimes surfaced with various types of mats, films, foils, and mineral granules.
Moisture Contour Map: a map used to graphically define the location of
moisture within a roof assembly after a moisture scan has been performed.
Moisture Relief Vent: a venting device installed through the roofing membrane
to relieve moisture vapor pressure from within the roofing system.
Moisture Scan: the use of a mechanical device (capitance, infrared, or nuclear)
to detect the presence of moisture within a roof assembly. (See Non-Destructive
Testing.)
Mole Run: a meandering buckle or ridging in a roof membrane not associated
with insulation or deck joints.
Monolithic: formed from or composed of a single material; seamless.
Monomer: a simple molecule that is capable of combining with a number of like
or unlike molecules to form a polymer.
Mop-and-Flop: an application procedure in which roofing elements (insulation
boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to
their ultimate locations, are coated with adhesive or bitumen, and are then turned
over and applied to the substrate.
Mopping: the application of hot bitumen, with a roofer's hand mop or mechanical
applicator, to the substrate or to the felts of a bituminous membrane.
Solid Mopping: a continuous mopping of a surface.
Spot Mopping: a mopping pattern in which hot bitumen is applied
in roughly circular areas, leaving a grid of unmapped, perpendicular
bands on the roof.
Sprinkle Mopping: a random mopping pattern in which heated
bitumen beads are strewn onto the substrate with a brush or mop.
Strip Mopping: a mopping pattern in which hot bitumen is applied
in parallel bands.
Mud Cracking: surface cracking of a material whereby the degraded material
appears similar to dried, cracked earthen mud.
Mud Slab: a layer of concrete, typically 2 to 6 inches (51 to 1 52mm)thick, used
as the substrate for membrane waterproofing.
Multiple Coat: two or more layers of coating applied to a substrate.
Moisture Vapor Transmission :The rate of movement of moisture vapor in unit
time through a unit area of a membrane.
NAHB: National Association of Home Builders
Nailer: (commonly referred to as Blocking) a piece or pieces of dimensional
lumber and/or plywood secured to the structural deck or walls, which provide a
receiving medium for the fasteners used to attach membrane or flashing.
Generally, it is recommended that nailers be the same thickness as the adjacent
insulation, and may be treated with a non-oil-borne preservative, and be of
sufficient width to fully support the horizontal flashing flange of a metal flashing
(where used).
Nailing: the application of nails. May be: (1) exposed nailing of roofing wherein
nail heads are exposed to the weather; (2) concealed nailing of roofing wherein
nail heads are concealed from the weather by an overlapping material.
NBP: acrylonitrile butadiene polymer blend. One proprietary NBP membrane is
commonly referred to as nitrile butadiene copolymer.
Needle Punched Fabric: a fabric where barbed needles (in multiple punches)
achieve mechanical bonding/locking or carding of fibers.
Negative Side Waterproofing: an application wherein the waterproofing system
and the source of hydrostatic pressure are on opposite sides of the structural
element.
Neoprene: a synthetic rubber (polychloroprene) used in liquid-applied and
sheetapplied
elastomeric roof membranes or flashings.
Nesting: a method of reroofing with new asphalt shingles over existing shingles
in which the top edge of the new shingle is butted against the bottom edge of the
existing shingle.
Net Free Vent Area: the area, measured in square inches, open to unrestricted
air flow and commonly used as a yardstick to measure relative vent performance.
Newton (N): Sl unit of measure for force.
NICA: National Insulation Contractors Association
Night Seal (or Night Tie-Of0: a material and/or method used to temporarily seal
a membrane edge during construction to protect the roofing assembly in place
from water penetration. Usually removed when roofing application is resumed.
Nineteen-lach Selvage (Double-Coverage or Split-Sheet): a prepared roofing
sheet with a 17 inch (430mm) granule surfaced exposure and a non-granule
surfaced 19 inch (485mm) selvage edge. This material is sometimes referred to
as SIS, double-coverage, or according to ASTM Standard D 371-89, Standard
Specification for Asphalt Roll Roofing (Organic Felt) Surfaced with Mineral
Granules,Wide Selvage.
Ninety-Pound: a prepared organic felt roll roofing with a granule surfacing that
has a mass of approximately 90 pounds per 100 square feet, (4400 g/m2).
NIST: National Institute of Standards and Technology
Nitrile Alloy: an elastomeric material of synthetic non-vulcanizing polymers.
Nitrile Rubber: a membrane whose predominant resinous ingredient is a
synthetic rubber made by the polymerization of acrylonitrile with butadiene.
Noble: in reference to metal, inert; opposite of active.
No-Cutout Shingles: shingles consisting of a single solid strip with no cutouts.
Non-Breathing Membrane: a membrane that does not allow significant amounts
of water vapor or air to pass through; which has a perm rating 1.0 or less per
ASTM E 96, Procedure E.
Non-Destructive Testing (NOT): a method to evaluate the disposition, strength,
or composition of materials without damaging the object under test. Typically
used to evaluate moisture content in roofing assemblies, the three common test
methods are electrical capacitance, infrared thermography, and nuclear
backscatter.
Non-Flammable: liquid having no measurable flash point.
Non-Friable: a material that, when dry, cannot be crumbled, pulverized or
reduced to powder by hand pressure.
Non-Oxidizing: a material which resists oxidation in exterior exposures or
accelerated weathering.
Non-Traffic Bearing: for waterproofing purposes, a membrane system requiring
some form of protection barrier and wearing surface.
Non-Volatile Content: that portion of a material that does not evaporate under
normal ambient conditions.
Non-Vulcanized Membrane: a membrane manufactured from thermoplastic
compounds that retains its thermoplastic properties throughout the service life of
the membrane.
Nonwoven: a term used to describe the random arrangement of reinforcing
fibers (glass, polyester, etc.) in a mat or scrim.
NRCA: National Roofing Contractors Association
NTRMA: National Tile Roofing Manufacturers Association
Nuclear Testing (Nuclear Back-Scatter): a device that contains a radioactive
source to emit high velocity neutrons into a roof system. Reflecting neutrons are
measured by a gauge that is used to detect moisture.
Nylon: generic name for a family of polyamide polymers, used as a scrim in
some fabric-reinforced sheeting.
Off-Ratio Foam: SPF which has excess isocyanate or resin. Off-ratio will not
exhibit the full physical properties of normal SPF.
Open Time: the period of time after an adhesive has been applied and allowed
to dry, during which an effective bond can be achieved by joining the two
surfaces.
Open Valley: a method of valley construction in which the steep-slope roofing on
both sides are trimmed along each side of the valley, exposing the valley
flashing.
Orange Peel Surface Texture: the surface shows a fine texture and is
compared to the exterior skin of an orange. This surface is considered
acceptable for receiving a protective coating. The theoretical coverage rate
cannot be used without adding a minimum 10% additional material to adequately
cover the orange peel texture.
Organic: being or composed of hydrocarbons or their derivatives originating from
plant or animal matter.
Organic Felt: an asphalt roofing base material manufactured from cellulose
fibers.
Organic Shingle: an asphalt shingle reinforced with material manufactured from
cellulose fibers.
ORNL: Oak Ridge National Laboratory
Osmosis: the diffusion of fluids through a semi-permeable membrane or porous
partition.
Overspray: undesirable depositions of airborne spray loss.
Overspray Surface Texture: the surface shows a linear coarse textured pattern
and/or a pebbled surface. This surface is generally downwind of the sprayed
polyurethane path and is unacceptable for proper coating coverage and
protection, if severe. The minimum percentage of additional material to be added
will vary from 25% to 50% depending upon the type of surface texture.
Ozone Resistance: the ability of a material to resist the deteriorating effects of
ozone exposure.
Pan: the bottom flat part of a roofing panel which is between the ribs of the panel.
Pan Former: power roll-forming equipment that produces a metal roofing panel
from a flat sheet.
Parapet Wall: that part of a perimeter wall immediately adjacent to the roof
which extends above the roof.
Parge: in masonry construction, a coat of cement mortar on the face of rough
masonry, the earth side of foundation and basement walls, or the like.
Partially-Attached: a roofing assembly in which the membrane has been "spot
affixed" to a substrate, usually with an adhesive or a mechanical device.
Pascal (N/m2): Sl unit of measure for force per unit area.
Pass: 1) a layer of material, usually applied by the spray method, that is allowed
to reach cure before another layer (pass) is applied; 2) a term used to explain a
spray motion of the foam gun in the application of the spray polyurethane foam
(SPF) material. The speed of the "pass" controls the thickness of the SPF.
Pass Line: the junction of two passes of SPF. A distinct line is formed by the top
skin of the bottom pass and the next pass adhering to this skin.
Peel Strength: the average force (or force per unit width) required to peel a
membrane or other material from the substrate to which it has been bonded.
Penetration: (1) any object passing through the roof; (2) the consistency
(hardness) of a bituminous material expressed as the distance, in tenths of a
millimeter (0.1 mm), that a standard needle penetrates vertically into a sample of
material under specified conditions of loading, time, and temperature.
Percent Elongation: in tensile testing, the increase in the gauge length of a
specimen measured at or after fracture of the specimen within the gauge length.
Usually expressed as a percentage of the original gauge length.
Perlite: an aggregate used in lightweight insulating concrete and in preformed
perlitic insulation boards, formed by heating and expanding siliceous volcanic
glass.
Perm: a unit of water vapor transmission defined as 1 grain of water vapor per
square foot per hour per inch of mercury pressure difference (1 inch of mercury =
0.49 psi). The formula for perm is: P = Grains of Water Vapor/Square
Foot.Hour~lnch Mercury (P = grain~in/ft2.h~in Hg [P = ng/(Pa~s~m)]).
Permeability: (1) the capacity of a porous material to conduct or transmit fluids;
(2) the amount of a fluid moving through a barrier in a unit time, unit area, and
unit pressure gradient not normalized for, but directly related to, thickness.
Permeance: the rate of water vapor transmission per unit area at a steady state
through a material, membrane or assembly, expressed in Grain/Square
Foot.Hour~lnch Mercury (grain/ft2.h~in Hg [ng/Pa~a~m2]).
pH: a measure of acidity/alkalinity of aqueous mixtures. A measure of pH 7 is
neutral, lower is more acidic.
Phased Application: the installation of separate roof system or waterproofing
system component(s) during two or more separate time intervals. Application of
surfacings at different time intervals are typically not considered phased
application. (See Surfacing.).
Picture Framing: a square or rectangular pattern of buckles or ridges in a roof
covering generally coinciding with insulation or deck joints; generally, a function
of movement of the substrate.
Pigment: fine solid particles, which are insoluble in the vehicle, used to impart
color in a coating.
PIMA: Polyisocyanurate Insulation Manufacturers Association.
Pinhole: a tiny hole in a coating, film, foil, membrane, or laminate.
Pipe Boot: prefabricated flashing piece used to flash around circular pipe
penetrations.
Pitch: see Coal Tar, Incline, and Roof Slope.
Pitch-Pocket (Pitch-Pan): a flanged, open bottomed enclosure made of sheet
metal or other material, placed around a penetration through the roof, filled with
grout and bituminous or polymeric sealants to seal the area around the
penetration.
Pittsburgh Lock Seam: a method of interlocking metal, usually at a slope
change.
Plastic Cement: a roofing industry generic term used to describe Type I asphalt
roof cement that is a trowelable mixture of solvent-based bitumen, mineral
stabilizers, other fibers and/or fillers. Generally, intended for use on relatively low
slopes—not vertical surfaces. (Also see Asphalt Roof Cement and Flashing
Cement.).
Plastic Film: a flexible sheet made by the extrusion of thermoplastic resins.
Plasticizer: a material, frequently solvent-like, incorporated in a plastic or a
rubber to increase its ease of workability, flexibility, or extensibility.
Plastomeric: a plastic-like polymer consisting of any of various complex organic
compounds produced by polymerization, and capable of being molded, extruded,
or cast into various shapes or films.
Pliability: the material property of being flexible or moldable.
Ply: a layer of felt, ply sheet, or reinforcement in a roof membrane or roof
system.
PMR: Protected Membrane Roof.
Polychloroprene: see Neoprene.
Polyester: a polymeric resin which is generally cross-linked or cured and made
into a variety of plastic materials and products. Polyester fibers are widely used
as the reinforcing medium in reinforced membranes. (See Polyester Fiber.)
Polyester Fiber: a synthetic fiber usually formed by extrusion. Scrims made of
polyester fiber are used for fabric reinforcement.
Polyisobutylene (PIB): a product formed by the polymerization of isobutylene.
May be compounded for use as a roof membrane material.
Polymer: a natural or synthetic chemical compound of high molecular weight, or
a mixture of such compounds, formed when monomers (small individual
molecules) are combined to form large long-chain molecules.
Polymer Modified Bitumen: See Modified Bitumen.
Polymeric Methylene Diphenyl Diisocyanate (PMDI): component A in SPF. An
organic chemical compound having two reactive isocyanate (-N=C=O) groups. It
is mixed with the B component to form polyurethane.
Polymerization: the process whereby monomers are combined to form large,
chainlike molecules.
Polypropylene: a tough, lightweight plastic made by the polymerization of
Highpurity propylene gas.
Polyvinyl Chloride (PVC): a synthetic thermoplastic polymer prepared from
vinylchloride. PVC can be compounded into flexible and rigid forms through the
use of plasticizers, stabilizers, fillers, and other modifiers; rigid forms are used in
pipes; flexible forms are used in the manufacture of sheeting and roof membrane
materials.
Ponding: the excessive accumulation of water at low-lying areas on a roof.
Pop Rivet: a relatively small headed pin with an expandable head for joining
relatively light gauge metal.
Popcorn Surface Texture: the surface shows a coarse texture where valleys
form sharp angles. This surface is unacceptable for proper coating andprotection.
Positive Drainage: the drainage condition in which consideration has been
made during design for all loading deflections of the deck, and additional roof
slope has been provided to ensure drainage of the roof area within 48 hours of
rainfall, during ambient drying conditions.
Positive Side Waterproofing: an application where the waterproofing systems
and the source of the hydrostatic pressure are on the same side of the structural
element.
Pot Life: the period of time during which a multi-component or catalytically cured
material remains suitable for application after being mixed.
Pourable Sealer: a type of sealant often supplied in two parts, and used at
difficult-to-flash penetrations, typically in conjunction with pitch-pockets to form a
seal.
Polyurethane Spray Foam : Polyurethane foam is a rigid closed cell plastic
created by a combination of two liquid components which react in seconds and
can be walked on in a matter of minutes. Polyurethane foam stops leaks and
ponding water and insulates – creating a lightweight, seamless, waterproof
“blanket” over the structure.
Ponding :The term used to describe a pool of water at least 1/2" deep that
remains in an area at least 100 square feet for one full day (24 hours) after a
rain.
Pre-Tinning: coating a metal with solder or tin alloy, prior to soldering or brazing
it.
Press Brake: a machine used in cold-forming sheet metal or strips of metal into
desired profiles.
Prestressed Concrete: concrete in which the reinforcing cables, wires, or rods
in the concrete are tensioned before there is load on the member, holding the
concrete in compression for greater strength.
Primer: (1) a thin, liquid-applied solvent-based bitumen that may be applied to a
surface to improve the adhesion of subsequent applications of bitumen; (2) a
material which is sometimes used in the process of seaming single-ply
membranes to prepare the surfaces and increase the strength (in shear and
peel) of the field splice.
Proportioner: the basic pumping unit for SPF or two component coating
systems. Consists of two positive displacement pumps designed to dispense two
components at a precisely controlled ratio.
Protected Membrane Roof (PMR): an insulated and ballasted roofing assembly,
in which the insulation and ballast are applied on top of the membrane
(sometimes referred to as an "inverted roof assembly").
Psychrometer: a device for measuring ambient humidity by employing a dry
bulb thermometer and a wet bulb thermometer.
Psychrometric Chart: a diagram relating the properties of humid air with
temperature.
Puncture Resistance: extent to which a material is able to withstand the action
of a sharp object without perforation.
Purlin: horizontal secondary structural member that transfers loads from the
primary structural framing.
PVC: Polyvinyl Chloride.
Ply :The term used to describe a layer of felt in a foam roofing (built-up roof
membrane) system. For example, a four-ply membrane system has four plies
felt.
Plywood :A structural material made of layers of wood glued together, usually
with the grains of adjoining layers at right angles to each other.
pH: a measure of acidity/alkalinity of aqueous mixtures. A measure of pH 7 is
neutral, lower is more acidic.
Phased Application: the installation of separate roof system or waterproofing
system component(s) during two or more separate time intervals. Application of
surfacings at different time intervals are typically not considered phased
application. (See Surfacing.)
Picture Framing: a square or rectangular pattern of buckles or ridges in a roof
covering generally coinciding with insulation or deck joints; generally, a function
of movement of the substrate.
Pigment: fine solid particles, which are insoluble in the vehicle, used to impart
color in a coating.
PIMA: Polyisocyanurate Insulation Manufacturers Association
Pinhole: a tiny hole in a coating, film, foil, membrane, or laminate.
Pipe Boot: prefabricated flashing piece used to flash around circular pipe
penetrations.
Pitch: see Coal Tar, Incline, and Roof Slope.
Pitch-Pocket (Pitch-Pan): a flanged, open bottomed enclosure made of sheet
metal or other material, placed around a penetration through the roof, filled with
grout and bituminous or polymeric sealants to seal the area around the
penetration.
Pittsburgh Lock Seam: a method of interlocking metal, usually at a slope
change.
Plastic Cement: a roofing industry generic term used to describe Type I asphalt
roof cement that is a trowelable mixture of solvent-based bitumen, mineral
stabilizers, other fibers and/or fillers. Generally, intended for use on relatively low
slopes—not vertical surfaces. (Also see Asphalt Roof Cement and Flashing
Cement.)
Plastic Film: a flexible sheet made by the extrusion of thermoplastic resins.
Plasticizer: a material, frequently solvent-like, incorporated in a plastic or a
rubber to increase its ease of workability, flexibility, or extensibility.
Plastomeric: a plastic-like polymer consisting of any of various complex organic
compounds produced by polymerization, and capable of being molded, extruded,
or cast into various shapes or films.
Pliability: the material property of being flexible or moldable.
Ply: a layer of felt, ply sheet, or reinforcement in a roof membrane or roof
system.
PMR: Protected Membrane Roof.
Polychloroprene: see Neoprene.
Polyester: a polymeric resin which is generally cross-linked or cured and made
into a variety of plastic materials and products. Polyester fibers are widely used
as the reinforcing medium in reinforced membranes. (See Polyester Fiber.)

Polyester Fiber: a synthetic fiber usually formed by extrusion. Scrims made of
polyester fiber are used for fabric reinforcement.
Polyisobutylene (PIB): a product formed by the polymerization of isobutylene.
May be compounded for use as a roof membrane material.
Polymer: a natural or synthetic chemical compound of high molecular weight, or
a mixture of such compounds, formed when monomers (small individual
molecules) are combined to form large long-chain molecules.
Polymer Modified Bitumen: See Modified Bitumen.
Polymeric Methylene Diphenyl Diisocyanate (PMDI): component A in SPF. An
organic chemical compound having two reactive isocyanate (-N=C=O) groups. It
is mixed with the B component to form polyurethane.
Polymerization: the process whereby monomers are combined to form large,
chainlike molecules.
Polypropylene: a tough, lightweight plastic made by the polymerization of
Highpurity propylene gas.
Polyvinyl Chloride (PVC): a synthetic thermoplastic polymer prepared from
vinylchloride. PVC can be compounded into flexible and rigid forms through the
use of plasticizers, stabilizers, fillers, and other modifiers; rigid forms are used in

pipes; flexible forms are used in the manufacture of sheeting and roof membrane
materials.
Ponding: the excessive accumulation of water at low-lying areas on a roof.
Pop Rivet: a relatively small headed pin with an expandable head for joining
relatively light gauge metal.
Popcorn Surface Texture: the surface shows a coarse texture where valleys
form sharp angles. This surface is unacceptable for proper coating and
protection.
Positive Drainage: the drainage condition in which consideration has been
made during design for all loading deflections of the deck, and additional roof
slope has been provided to ensure drainage of the roof area within 48 hours of
rainfall, during ambient drying conditions.
Positive Side Waterproofing: an application where the waterproofing systems
and the source of the hydrostatic pressure are on the same side of the structural
element.
Pot Life: the period of time during which a multi-component or catalytically cured
material remains suitable for application after being mixed.
Pourable Sealer: a type of sealant often supplied in two parts, and used at
difficult-to-flash penetrations, typically in conjunction with pitch-pockets to form a
seal.
Pre-Tinning: coating a metal with solder or tin alloy, prior to soldering or brazing
it.
Press Brake: a machine used in cold-forming sheet metal or strips of metal into
desired profiles.
Prestressed Concrete: concrete in which the reinforcing cables, wires, or rods
in the concrete are tensioned before there is load on the member, holding the
concrete in compression for greater strength.
Primer: (1) a thin, liquid-applied solvent-based bitumen that may be applied to a
surface to improve the adhesion of subsequent applications of bitumen; (2) a
material which is sometimes used in the process of seaming single-ply
membranes to prepare the surfaces and increase the strength (in shear and
peel) of the field splice.
Proportioner: the basic pumping unit for SPF or two component coating
systems. Consists of two positive displacement pumps designed to dispense two
components at a precisely controlled ratio.
Protected Membrane Roof (PMR): an insulated and ballasted roofing assembly,
in which the insulation and ballast are applied on top of the membrane
(sometimes referred to as an "inverted roof assembly").
Psychrometer: a device for measuring ambient humidity by employing a dry
bulb thermometer and a wet bulb thermometer.
Psychrometric Chart: a diagram relating the properties of humid air with
temperature.
Puncture Resistance: extent to which a material is able to withstand the action
of a sharp object without perforation.
Purlin: horizontal secondary structural member that transfers loads from the
primary structural framing.
PVC: Polyvinyl Chloride.
“R” Factor :The formula for determining thermal resistance. Each roof or wall
material has a pre-calculated resistance value which, when added together,
represents the composite system’s total resistance to heat flow.
Seal: (1) a generic term for a function that prevents or controls the passage of
water; (2) to secure a roof or structure from the entry of moisture.
Sealant: a single- or multi-component polymeric or bituminous-based material
used to weatherproof many types of construction joints where moderate
movement is expected. The material comes in various grades: pourable,
selfleveling,
non-sag, gun grade, and cured or uncured tapes.
Sealer: a coating designed to prevent absorption of finish coats into porous
surfaces; a coating designed to prevent bleeding.
Sealing Washer: a rubber or neoprene washer, sometimes metal-backed,
typically assembled on a fastener to prevent water from migrating into and
through the fastener hole.
Seam: a joint formed by mating two separate sections of material. Seams may
be made or sealed in a variety of ways, including adhesive bonding, hot-air
welding, solvent welding, using adhesive tape, sealant, etc.
Seamless :Polyurethane foam is applied as a liquid, creating a single monolithic
membrane that covers the entire roof. There are no seams or joints – the source
of the majority of leaks in traditional roofs.
Self-Adhering Membrane: a membrane that can adhere to a substrate and to
itself at overlaps without the use of an additional adhesive. The undersurface of a
self-adhering membrane is protected by a release paper or film, which prevents
the membrane from bonding to itself during shipping and handling.
Service Temperature Limits: the minimum or maximum temperature at which a
coating, SPF, or other material will perform satisfactorily.
Side Lap: the continuous longitudinal overlap of neighboring like materials. (See
Figures 23 and 24.)
Slope :This is the angle of the roof that is often called the “fall area.” Most roofs
built in the 1960's, 70's and 80's were built with 4/12 to 6/12 roof slopes.
Single-Ply Membranes: roofing membranes that are field applied using just one
layer of membrane material (either homogeneous or composite) rather than
multiple layers.
Single-Ply Roofing: a roofing system in which the principal roof covering is a
single layer flexible membrane, often of thermoses, thermoplastic, or polymer
modified bituminous compounds.
Single-Ply System: generally, there are six types of single-ply roofing systems:
1) Fully-adhered
2) Loose-laid
3) Mechanically-fastened
4) Partially-adhered
5) Protected membrane roof
6) Self-adhering
Slope – Low :Indicates a roof slop of 1/2 inch per foot to 1/2 inch per foot.
SPF :An acronym for “Sprayed Polyurethane Foam” – This sophisticated, rigid,
leak and weather resistant material is used for foam roofing systems and as an
excellent insulation .
Softening Point: the temperature at which bitumen becomes soft enough to
flow, as determined by a closely defined method (ASTM Standard test method D
36 or D 3461).
Solids Content: the percentage of non-volatile matter in a coating or mastic
formulation; may be expressed as a volume or weight percent.
Solvent: liquid used to dissolve or disperse film-forming constituents, and which
evaporates during drying and does not become a part of the dried film.
Specification: a statement of requirements for a given job or project. Usually
describes products, materials, and processes to be used. A specification may
also contain terms of the contract.
SPF: sprayed polyurethane foam.
SPF Compound: a term used to describe the raw materials (isocyanate and
resin) used to make polyurethane foam.
Spread Coating: a manufacturing process in which membranes are formed
using a liquid compound, prepared in mixers and then fed to individual coalers.
The mixture is spread onto a supporting reinforcement base layer. After coating,
the material passes through a channel causing it to change from a paste to a
solid membrane, in sheet form.
SPRI: Single Ply Roofing Institute
Spunbond: a type of nonwoven fabric formed from continuous fiber filaments
that are laid down and bonded continuously, without an intermediate step.
Square: 100 square feet (9.29 m2) of roof area.
Styrene Butadiene Rubber: high molecular weight polymers having rubber-like
properties, formed by the random copolymerization of styrene and butadiene
monomers.
Styrene Butadiene Styrene Copolymer (SBS): high molecular weight polymers
that have both thermoses and thermoplastic properties, formed by the block
copolymerization of styrene and butadiene monomers. These polymers are used
as the modifying compound in SBS polymer modified asphalt roofing membranes
to impart rubber-like qualities to the asphalt.
Substrate: the surface upon which the roofing or waterproofing membrane is
applied (e.g., in roofing, the structural deck or insulation).
Sump: an intentional depression around a roof drain or scupper that serves to
promote drainage.
Surface Conductance: a unit of heat flow or heat exchange between a material
and the air around it. Ventilation over a surface will decrease the thickness of the
air film and reduce the thermal effect (increase the heat flow).
Surface Cure: curing or vulcanization that occurs in a thin layer on the surface of
a manufactured polymeric sheet or other items.
Surface Dryness: surface dryness can be evaluated qualitatively by taping an
18 inch by 18 inch (0.46 m by 0.46 m) clear 4 mil polyethylene sheet to a
concrete surface, and observing the moisture that may collect on the underside
of the polyethylene sheet. Additional details of this procedure may be found in
ASTM D 4263.
Surface Texture: the resulting surface from the final pass of SPF. The following
terms are used to describe the types of SPF surfaces: smooth surface texture,
orange peel surface texture, coarse orange peel surface texture, verge of
popcorn texture, popcorn surface texture, treebark surface texture, and
oversprayed surface texture.
Surfacing: the top layer or layers of a roof covering, specified or designed to
protect the underlying roofing from direct exposure to the weather.
Surfactant: short for "surface active agent." Used to alter the surface tension of
liquids. An ingredient in SPF formulations to aid in mixing and controlling cell
size.
Substrate :The material or surface (wood, metal, concrete, etc.) to which the
roofing or waterproofing membrane is applied.
Tar :A heavy, dark, oily, viscous material, consisting mainly of hydrocarbons,
produced by the destructive distillation of organic substances such as wood, coal
or peat. No insulation value.
Tab: the exposed portion of strip shingles defined by cutouts. (See Figure 25.)
Talc: whitish powder applied at the factory to the surface of some roofing
materials (e.g., vulcanized EPDM membranes), used as a release agent to
prevent adhesion of the membrane to itself.
Tapered Edge Strip: a tapered insulation strip used to (1) elevate and slope the
roof at the perimeter and at curbs, and (2) provide a gradual transition from one
layer of insulation to another.
Taping: (1) the technique of connecting joints between insulation boards or deck
panels with tape; (2) the technique of using self-adhering tape-like materials to
seam or splice single-ply membranes.
Tar: a brown or black bituminous material, liquid or semi-solid in consistency, in
which the predominating constituents are bitumens obtained as condensates in
the processing of coal, petroleum, oil-shale, wood, or other organic materials.
Tar Boils: bubbles of moisture vapor encased in a thin film of bitumen, also
known as "blackberries."
Tarred Felt: see Coal Tar Felt.
Tear-Off and Reroof: the removal of all roof system components down to the
structural deck, followed by installation of a completely new roof system.
Tear Resistance: the load required to tear a material, when the stress is
concentrated on a small area of the material by the introduction of a prescribed
flaw or notch. Expressed in psi (pounds force) per inch width or kN/m (kilonewton
per meter width).
Tear Strength: the maximum force required to tear a specimen.
Tensile Fatigue Resistance: the ability of a given membrane material to resist
"fatigue" and/or other damage (such as loss of elasticity) caused by the alternate
stretching and relaxing of the material over a period of time.
Tensile Strength: the maximum force (longitudinal pulling stress) a material can
bear without tearing or breaking apart.
Tensile Test: a test in which a specimen is subjected to increasing longitudinal
pulling stress until fracture occurs.
Termination: the treatment or method of anchoring and/or sealing the free edges
of the membrane in a roofing or waterproofing system.
Terne: an alloy of lead and tin, used to coat sheets of carbon steel or stainless
steel for use as metal roofing sheet.
Terra Cotta: low-fired clay, either glazed or unglazed.
Test Cut: a sample of the roof, which may contain all components or just the
membrane, usually used to diagnose the condition of the existing membrane,
evaluate the type and number of plies or number of membranes, or rates of
application such as determine the weight of the average interply bitumen
mappings.
Thatch Roof: the covering of a roof usually made of straw, reed, or natural
foliage (palms) bound together to shed water.
Therm: a unit of heat equivalent to 100,000 BTUs (105.6-106). Commonly used
by utilities in quoting prices or costs.
Thermal Barrier: a material applied over polyurethane foam designed to slow
the temperature rise of the foam during a fire and delay its involvement in the fire.
Thermal barriers for use with SPF must have a time rating of not less than 15
minutes.
Thermal Block: a compression-resistant insulation block installed between the
structural steel and the panel to maintain insulation value.
Thermal Conductance (C): a unit of heat flow that is used for specific
thicknesses of material or for materials of combination or composite construction,
such as laminated insulation. The formula for thermal conductance is:
Thermal Conductivity (k): the heat energy that will be transmitted by conduction
through 1 square foot of 1 inch thick homogeneous material in one hour when
there is a difference of 1 degree Fahrenheit perpendicularly across the two
surfaces of the material. The formula for thermal conductivity is: k = Btu/Square
FooVlnch /Hour/Degree Fahrenheit
Thermal Image: a visual representation of temperature distribution over a
surface area. The image is displayed on a screen, presenting the response to
infrared light waves.
Thermal Insulation: a material applied to reduce the flow of heat.
Thermal Movement: changes in dimension of a material as a result of
temperature changes.
Thermal Resistance (R): an index of a material's resistance to heat flow; it is the
reciprocal of thermal conductivity (k) or thermal conductance (C). The formula for
thermal resistance is:
Thermal Shock: the stress-producing phenomenon resulting from sudden
temperature changes in a roof membrane when, for example, a cold rain shower
follows brilliant hot sunshine, which may result in sudden cooling or rapid
contraction of the membrane.
Thermal Stress: stress introduced by uniform or non-uniform temperature
change in a structure or material that is contained against expansion or
contraction.
Thermogram: a visible light record of the display of an infrared camera system
via a Polaroid print, 35mm film, video tape, or computer generated image.
Thermography: a technique for producing heat "pictures" from the radiant
energy emitted from stationary or moving objects without in any way influencing
the temperatures of the objects under view. The electronic generation and
display of a visible image of an infrared spectrum.
Thermoplastic: materials that soften when heated and harden when cooled.
This process can be repeated provided that the material is not heated above the
point at which decomposition occurs.
Thermoplastic Olefin Membrane (TPO): a blend of polypropylene and
ethylene-propylene polymers. Colorant, flame retardants, UV absorbers, and
other proprietary substances which may be blended with the TPO to achieve the
desired physical properties. The membrane may or may not be reinforced.
Thermoset: a material that solidifies or "sets" irreversibly when heated. This
property is usually associated with cross-linking of the molecules induced by heat
or radiation.
Thinner: a liquid used to reduce the viscosity of coatings or mastic. Thinners
evaporate during the curing process. Thinners may be used as solvents for
clean-up of equipment.
Thixotropic: having the property of decreasing viscosity with increasing shear
stress. A coating is thixotropic if it thins with stirring or pumping but thickens
when movement ceases.
Thread Count: the number of threads per inch in each direction, with the warp
mentioned first, and the fill second, (e.g., a thread count of 20 x 10 means 20
threads per inch [25.4mm] in the warp and 10 threads per inch [25.4mm] in the fill
direction).
Through-Wall Flashing: a water-resistant material, which may be metal or
membrane, extending through a wall and its cavities, positioned to direct water
entering the top of the wall or cavity to the exterior, usually through weep holes.
Tie-Off: (in roofing and waterproofing) the transitional seal used to terminate a
roofing or waterproofing application at the top or bottom of flashings, or by
forming a watertight seal with the substrate, membrane or adjacent roofing or
waterproofing system.
TIMA: Thermal Insulation Manufacturers Association
Toggle Bolt: a two-piece assembly consisting of a threaded bolt and an
expanding clip that can fit through a drilled hole. The clip can spring outward to
provide anchorage from the blind side.
Tongue and Groove Planks: one of the oldest types of dimensional structural
wood used as roof decking. The sides are cut with convex and concave grooves
so adjacent planks may join in alignment with each other to form a uniform roof
deck.
TPA: Tri-Polymer Alloy.
TPO: Thermoplastic Olefin.
Traffic Bearing: in waterproofing, a membrane formulated to withstand a
predetermined amount of pedestrian or vehicular use with separate protection
and a wear course.
Transverse Seam: the joint between the top of one metal roof panel and the
bottom of the next panel, which runs perpendicular to the roof slope.
Treebark Surface Texture: the surface shows a coarse texture where valleys
from sharp angles. This surface is unacceptable for proper coating and
protection.
Tuckpointing: the process of removing deteriorated mortar from an existing
masonry joint and troweling new mortar or other filler into the joint.
Two-Part System: a coating of SPF formed by the mixing and (usually) the
reaction of two different materials.
Thermal Conductance (C) :A specific unit of heat flow that is used to determine
the specific thickness of material or for materials of combination construction,
such as laminated insulation .
Thermal Conductivity (k) :A unit for comparing or calculating quantities of heat.
Thermal Conductivity is the amount of heat necessary to raise the temperature of
one gram or one pound of water from zero to one degree Centigrade.
Thermal Resistance (R) :The index of a material's resistance to heat flow; it is
the reciprocal of thermal conductivity (k) or thermal conductance (C).
Thermal Shock :Represents severe stress on and/or changes in a roof
membrane resulting from sudden fluctuations in temperature (i.e.: a pelting rain
storm followed by intense sunshine.)
Thermoplastic Olefin Membrane (TPO) :A proprietary blend of polypropylene
and ethylene-propylene polymers.
Tongue & Groove :Interlocking wooden boards with a groove on one side and a
ridge or tongue on the other.
Traffic Bearing Membrane: A membrane tested and formulated to withstand a
predetermined amount of use.
-Value: overall thermal conductance. U-value is equal to the inverse of the sum
of the R-value in a system (U = 1/R total). Units are Btu/Ft2.Hr.°F.
UBC: Uniform Building Code.
UL: Underwriters Laboratories, Inc.
UL Label: an identification label or seal affixed to a roofing product or package
with the authorization of Underwriters Laboratories, Inc. The presence of the
label indicates that the product has met certain performance criteria.
Ultimate Elongation: the amount a material stretches during tensile testing
before it ruptures. Usually expressed as a percentage of the original length.
Ultraviolet (UV): (1) situated beyond the visible spectrum, just beyond the violet
end, having wavelengths shorter than wavelengths of visible light and longer than
those of X-rays; (2) relating to, producing, or employing ultraviolet radiation.
Underlayment: an asphalt-saturated felt or other sheet material (may be
selfadhering)
installed between the roof deck and the roof system, usually used in a
steep-slope roof construction. Underlayment is primarily used to separate the
roof covering from the roof deck, to shed water, and to provide secondary
weather protection for the roof area of the building.
Underwriters Laboratories, Inc. (UL): an organization that tests, rates and
classifies roof assemblies for their resistance to: fire, impact, leakage, corrosion
of metal components, and wind uplift.
Uplift: seeWind Uplift.
Valley: the internal angle formed by the intersection of two sloping roof planes.
(See Figure 26)
Vapor Migration: the movement of water vapor from a region of high vapor
pressure to a region of lower vapor pressure.
Vapor Pressure: the pressure at any given temperature exerted by a vapor that
is in equilibrium with its liquid or solid form.
Vapor Retarder: material installed to impede or restrict the passage of water
vapor through a roof assembly.
Veneer: (1) a single wythe of masonry for facing purposes, may not be
structurally connected; (2) any of the thin layers of wood glued together to form
plywood.
Vent: an opening designed to convey air, heat, water vapor or other gas from
inside a building or a building component to the atmosphere.
Ventilation Short Circuit: (as it relates to a passive ventilation system where
the system is designed for air flow between intake and exhaust vents) a
ventilation short circuit occurs when air is introduced into the ventilation system
from an area higher than the intake vent thereby minimizing or defeating the
effectiveness of the intake vent. One example can be a gable vent in a
soffittoridge
ventilation system. Air intake from the gable vent can short circuit the stackeffect
draw of air through the soffit vents, and interrupt the thorough venting of
the roof cavity.
Ventilator: an accessory that is designed to allow for the passage of air.
Verge of Popcorn Texture: the verge of popcorn surface texture is the roughest
texture suitable for receiving the protective coating on a sprayed polyurethane
foam roof. The surface shows a texture where nodules are larger than valleys,
with the valleys relatively cured. This surface is acceptable for receiving a
protective coating only because of the relatively cured valleys. However, the
surface is considered undesirable because of the additional amount of coating
material required to protect the surface properly. The theoretical coverage rate
cannot be used without adding a minimum of 50% additional material.
Vermiculite: an aggregate used in lightweight insulating concrete, formed by the
heating and consequent expansion of a micaceous material.
Viscosity: the resistance of a material to flow under stress. For bitumen,
measured in centipoise. (See Viscous.)
Viscous: resistant to flow under stress. Viscous materials are usually cohesive,
and have a sticky consistency.
Void: an open space or break in consistency.
Volatile: descriptive of a substance which passes off easily as a gas or vapor,
evaporating quickly.
Volatile Organic Compounds (VOC): organic materials which evaporate at
normal temperatures and pressures; organic materials which have vapor
pressures greater than 0.1 mm Hg at one atmosphere.
Vulcanization: any of various processes by which natural or synthetic rubber or
other polymeric materials may be cured or otherwise treated (i.e., exposed to
chemicals, heat, or pressure) to render them non-thermoplastic, and which
improve their elastic and physical properties
UBC :An acronym for “Uniform Building Code.” The Uniform Building Code is the
most widely adopted building code in the world and is a proven document
meeting the needs of government units charged with enforcement of building
regulation. The UBC provides complete regulations covering all major aspects of
building design and construction relating to fire, life and structural safety.
Ultraviolet Rays (UV) :Invisible radiation wavelengths, or light rays, just beyond
the violet in the visible spectrum – wavelengths shorter than those of visible light
and longer than those of X-rays. These rays are potentially very damaging and
can contribute significantly to roof membrane degradation.
Waterproofing :Treatment or coating of a surface or structure to prevent the
penetration by water under hydrostatic pressure.
Water Absorption: the amount of water absorbed by a material after immersion
for a prescribed period of time. May be expressed as a percentage of the original
weight of the material.
Water Cure: a method of curing a material, such as concrete, by applying a fine
mist of water over the surface to control the rate of moisture evaporation from the
material.
Water Cutoff: see Cutoff.
Water Stop: a diaphragm used across a joint as a sealant, usually to prevent the
passage of water.
Water Table: the level within the ground below which the soil is saturated with
water.
Water Vapor Transmission: a measure of the rate of transmission of water
vapor through a material under controlled laboratory conditions of temperature
and humidity. Customary units are grains/h~ft2. (See ASTM Standard E 96.)
Waterproof: the quality of a membrane, membrane material, or other component
to prevent water entry.
Waterproofing: treatment of a surface or structure to prevent the passage of
water under hydrostatic pressure.
Wear Course: the top layer of surfacing that carries pedestrian or vehicular
traffic. Sometimes referred to as wearing surface.
Wear Surface: see Wear Course.
Weather Infiltration: the negative condition where rain or snow penetrate the
roof. The condition is typically wind-driven.
Weatherometer: an instrument used to subject material specimens to
accelerated weathering conditions.
Weep Holes: small openings whose purpose is to permit drainage of water that
accumulates inside a building component (e.g., a brick wall, skylight frame, etc.).
Weld: to join pieces of metal together by heat fusion.
Wet: a condition where free water is present in a substance.
Wet Bulb Temperature: the temperature of air as registered by a thermometer
whose bulb is covered by a water wetted wick. Units are °F.
Wet Film Thickness: the thickness, expressed in mils, of a coating or mastic as
applied but not cured. For comparison, see Dry Film Thickness.
Wicking: the process of moisture movement by capillary action, as contrasted to
movement of water vapor.
Wind Clip: a steep-slope roofing attachment device that fits over the butt end of
tile, slate, and stone to help secure individual roofing units from wind-uplift.
Wind Load: force exerted by the wind on a structure or part of a structure.
Wind Uplift: the force caused by the deflection of wind at roof edges, roof peaks
or obstructions, causing a drop in air pressure immediately above the roof
surface. This force is then transmitted to the roof surface. Uplift may also occur
because of the introduction of air pressure underneath the membrane and roof
edges, where it can cause the membrane to balloon and pull away from the deck.
Windward: being in or facing the direction toward which the wind is blowing. The
side exposed to the prevailing wind.
Wire Tie System: a scheme of attachment for steep-slope roofing units (e.g.,
tile, slate, and stone) utilizing fasteners (nails and/or screws) in conjunction with
wire to make up a concealed fastening system.
Work Slab: see Mud Slab.
Woven Valley: a method of valley construction in which shingles or roofing from
both sides of the valley extend across the valley and are woven together by
overlapping alternate courses as they are applied.
Wythe: a masonry wall, one masonry unit, a minimum of two inches thick.
Z section: a member formed from coiled steel stock in the shape of a "Z."
Zinc: a metal that has application considerations including high
Expansioncontraction rates and low-temperature restrictions