Glossary

abrasion resistance: The ability of a material to endure wear caused by friction or movement from
contact with people, machinery, or particles.

absorption: The property of a substance that allows it to take in liquids or gases, such as moisture,
into its body.

accelerated weathering: A test method that speeds up weathering effects on a specimen by exposing it to
controlled environmental conditions for a shorter time period.

acrylic coating: A water-based or solvent-based liquid finish made with acrylic binders and pigments
that dries into a protective film.

acrylic resin: A polymer made from acrylic or methacrylic compounds, often used as a base in coating or
latex formulations.

active metal (anodic): A type of metal that easily loses electrons to a noble metal when moisture is
present, making it prone to corrosion.

A-component (A-side): The isocyanate side of a two-part polyurethane system used in foams and
coatings.

adhere: To cause two materials to stick together by means of chemical bonding or mechanical
interlocking.

adhesion: The strength of the attachment between two surfaces joined together by chemical or mechanical
forces, often tested by shear or peel methods.

adhesive: A bonding material that securely joins two surfaces or materials together.

adhesive bond break: A release layer that prevents two surfaces from sticking together, allowing
movement between them.

AFA: Abbreviation for American Fiberboard Association.

AGC: Abbreviation for Associated General Contractors of America.

aged R-value: The thermal resistance of insulation determined after a period of aging or conditioning
to simulate long-term performance.

aggregate: Crushed stone, gravel, or similar mineral material used for surfacing or as a component in
concrete or roofing systems.

aggregate, lightweight (LWA): Low-density mineral materials such as pumice, perlite, or expanded shale
used to make lightweight concrete and products.

aging: The natural or accelerated process by which materials change in properties over time due to
environmental exposure.

AIA: Abbreviation for American Institute of Architects.

air barrier: See “air retarder.”

air barrier accessory: See “air retarder accessory.”

air barrier system: See “air retarder system.”

air infiltration: Unintended entry of outside air into a building driven by pressure
differences.

air leakage: The movement of air through the building enclosure, caused by pressure differences, either
inward (infiltration) or outward (exfiltration).

air leakage rate: The measured amount of air that moves through a building surface area under a set
pressure and time period.

air retarder: A material or assembly installed to reduce the passage of air through walls or
roofs.

air retarder accessory: A connecting piece that ensures continuity within an air-retarder
system.

air retarder system: The coordinated set of materials forming a continuous air-sealing barrier in a
building envelope.

air space: A gap or cavity between two elements in a wall, ceiling, or roof section.

air-impermeable insulation: An insulation classified as nearly airtight, with very low air permeance
per ASTM tests.

aliphatic polyurethane: A polyurethane made from straight or branched carbon chains, valued for its
color stability and resistance to sunlight.

aliphatic polyurethane coating: A topcoat that uses aliphatic isocyanates for weather-resistant
finishes usually applied outdoors.

alkalinity: The measure of a liquid’s ability to neutralize acids, primarily due to carbonate,
bicarbonate, and hydroxide content.

alligatoring: A surface cracking pattern that looks like alligator skin, occurring as coatings or
asphalt age and lose flexibility.

aluminized steel: Sheet steel protected by a bonded aluminum coating for corrosion and weather
resistance.

aluminum: A malleable, non-rusting metal commonly used for roofing and flashing components.

ambient temperature: The surrounding air temperature in a given environment.

analysis: The evaluation or determination of material composition or properties, frequently involving
sampling and testing.

anodic: A metal that readily donates electrons when paired with another metal in an electrolyte,
thereby undergoing corrosion to protect the cathodic material.

ANSI: Abbreviation for American National Standards Institute.

APA: The Engineered Wood Association (formerly American Plywood Association).

APC: The Plastics Division of the American Chemistry Council, formerly the American Plastics
Council.

APP: See “atactic polypropylene.”

application rate: The amount of coating, adhesive, or material applied per unit area during
installation.

application temperature: The temperature at which a product, such as hot asphalt, is placed during
installation.

apron flashing: Metal flashing used where a sloped roof meets a vertical wall or a steeper slope, to
deflect water away.

APC/SPFA: Former collaborative name for American Plastics Council and Spray Polyurethane Foam
Alliance.

architect: A licensed design professional responsible for designing and administering building
projects.

architectural panel: A type of metal roof panel fixed over a substrate and designed to shed water
efficiently.

architectural shingle: See “dimensional shingle.”

area divider: A raised, flashed structure used to separate roof sections or transition between
incompatible materials.

ARMA: Asphalt Roofing Manufacturers Association.

aromatic polyurethane: A polymer that contains aromatic rings, providing toughness but less UV
stability than aliphatic versions.

asbestos: A naturally occurring fibrous mineral once used for its strength and heat resistance.

ASC: Associated Specialty Contractors.

ASCE: American Society of Civil Engineers.

ASHI: American Society of Home Inspectors.

ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

asphalt: A dark, bituminous material derived from petroleum or natural deposits, used as a waterproof
binder in roofing.

asphalt, dead-level: Type I asphalt per ASTM D312, used on flat roofs.

asphalt, flat: Type II asphalt per ASTM D312, suitable for moderate-slope applications.

asphalt, steep: Type III asphalt per ASTM D312, designed for use on steeper roof slopes.

asphalt, special steep: Type IV asphalt per ASTM D312, engineered for higher temperatures and very
steep slopes.

asphalt, waterproofing: Asphalt that meets ASTM D449 standards and is used specifically for
waterproofing systems.

asphalt, air-blown: Asphalt whose properties are modified by blowing air through it while hot,
increasing its hardness and softening point.

asphalt emulsion: A mix of asphalt, water, and an emulsifying agent forming a stable suspension for use
in coatings or adhesives.

asphalt felt: A flexible sheet made by saturating or coating a felt base with asphalt, used in roofing
layers.

asphalt primer: A liquid asphalt material applied to improve adhesion between substrates and subsequent
roof layers.

asphalt roof cement: A dense, trowel-applied asphalt mix containing fillers and fibers used to bond or
repair roofing materials.

asphalt shingle: A shingle with a reinforced mat coated in asphalt and surfaced with mineral granules
for weather resistance.

ASTM International: A global organization that develops and publishes voluntary technical standards for
materials and products.

atactic polypropylene: A randomly structured polypropylene polymer used as a modifier in bitumen
roofing sheets.

attic: The open space or cavity between a roof deck and the ceiling below it.

AWPA: American Wood Protection Association (formerly American Wood Preservers Association).

backnailing: Concealed nailing beneath an overlapping roof layer to prevent slippage and protect
fasteners from weather exposure.

backrolling: Rolling over a freshly sprayed coating to improve adhesion and coverage.

backup plate: A rigid support plate placed under an overlap to ensure even compression at the
joint.

ballast: Heavy stone, pavers, or other materials that hold a roof membrane in place by their own
weight.

bar joist: See “steel joist.”

base coat: The first or foundational layer of a multi-layer coating system applied to a
surface.

base flashing (membrane base flashing): Strips of roof membrane material installed at points where a
roof meets a vertical surface, sealing the edge of the field membrane and extending up the wall.

base ply: The first layer in a built-up or modified bitumen roofing system to which additional layers
will be added.

base sheet: A saturated, coated, or impregnated felt that serves as the first ply in some low-slope
roofing systems.

basic wind speed: The three-second maximum wind gust measured 33 feet above the ground in Exposure C,
as defined in the ASCE 7 design standard.

batten: A thin strip of wood or metal used to fasten, support, or cover joints between roofing panels
or materials.

batten seam: A standing-seam roofing profile in which adjoining panels are secured and capped with a
batten or cover strip.

B-component (B-side): The resin or polyol component in a two-part polyurethane system used with an
isocyanate component to produce foam or coatings.

beam: A structural element, usually horizontal, designed to support loads by resisting bending
forces.

bearing plate: A plate placed beneath a structural member or fastener to distribute loads over a larger
surface area.

Bermuda seam: A metal roof panel configuration that has step-down ridges perpendicular to the roof
slope, creating a layered, shingled look.

bitumen: A group of dark, viscous materials—such as asphalt or coal tar—composed mainly of hydrocarbons
and used for roofing and waterproofing.

bituminous: Describes a material containing or treated with bitumen, such as bituminous felts or
pavements.

bituminous emulsion: A suspension of tiny bitumen droplets in water (or vice versa), stabilized with an
emulsifying agent for ease of application.

blanket insulation: Soft, fibrous insulation—often fiberglass—supplied in rolls or batts for walls and
roofs.

blast furnace slag: A nonmetallic by-product from the iron-making process, composed mainly of
silicates, used as aggregate or in cementitious materials.

blister: A raised area caused by trapped air, vapor, or moisture between roofing layers or between the
roof membrane and substrate.

blocking: Wood pieces integrated into roof assemblies, usually above the deck, providing fastening or
edge support for membranes, curbs, or insulation.

blowing agent: A substance that creates gas during heating or reaction, forming the cellular structure
of foam insulation materials.

bond: The adhesive connection between two materials; may also refer to a legal guarantee ensuring
performance or payment.

bonding agent: A coating or chemical applied to improve adhesion between a surface and the material
applied over it.

boot: A molded or flexible cover used around roof penetrations such as pipes to keep out water and
debris.

bracing: Supporting members, such as cables, frames, or rods, that stabilize structural components
against movement.

bridging: Occurs when roofing materials span unsupported gaps or fail to nest properly, resulting in
voids or uneven surfaces.

British thermal unit (Btu): The amount of heat required to raise the temperature of one pound of water
by one degree Fahrenheit.

broadcast: To distribute particles—such as granules or aggregates—uniformly over a surface.

brooming: The act of pressing a membrane or felt into adhesive using a broom or squeegee to ensure full
contact.

Btu: See “British thermal unit.”

buck: Refers to the reverse flow of runoff, where water runs upslope against a joint or seam instead of
down.

buckle: An elevated linear ridge or displacement in a roof membrane caused by movement, stress, or
moisture expansion beneath it.

building code: Official regulations establishing minimum standards for design, materials, and
construction of buildings for health and safety.

built-up roof (BUR): A multi-ply roofing system made of alternating layers of bitumen and reinforcement
sheets, topped with aggregate or coating for protection.

butt edge: The lower, visible edge of a shingle, tile, or shake when installed on a roof.

butt joint: The junction where two materials meet end-to-end without overlapping.

button punch: The process of pressing metal sheets together to create a dimple, securing them and
reducing slippage.

butyl rubber: A synthetic rubber formed from isobutylene and a small amount of isoprene, known for low
gas permeability and flexibility.

butyl tape: A flexible, adhesive strip made from butyl rubber, used to seal seams in metal roofing and
other joints.

calendering: A manufacturing process where molten material is passed between heated rollers to create
smooth, consistent sheets.

camber: A slight upward curvature in a structural member, deck, or surface to improve load performance
or drainage.

cant strip: A beveled strip set at the intersection of a horizontal and vertical surface to create a
smooth transition for membrane application.

cap flashing: A metal cover installed at the top edges of walls or base flashings to prevent moisture
intrusion.

cap sheet: The topmost ply in some built-up or modified-bitumen roofs, often surfaced with granules for
weather protection.

capillary action: The movement of liquid along narrow spaces or pores due to adhesive and cohesive
molecular forces, often against gravity.

catalyst: A chemical that triggers or accelerates a reaction without being consumed by it.

cathodic: The metal or component that accepts electrons (and resists corrosion) in a galvanic reaction,
as opposed to the anodic part.

caulking: The act of sealing joints and seams with a sealant to make them watertight and
airtight.

cavitation: The formation of vapor-filled cavities or bubbles in a liquid, usually due to rapid
pressure changes.

c-channel: A structural framing piece shaped like the letter “C,” used to support wall and roof
systems.

cellular concrete: A lightweight cementitious product made by combining Portland cement, water, and
foam to form an aerated mixture.

cellular glass insulation: A solid, closed-cell insulation product made by foaming glass powder; highly
resistant to moisture and fire.

cementitious wood fiber deck: A rigid panel made from wood fibers bonded with cement to create a
strong, sound-absorbing structural material.

centimeter (cm): A metric unit equal to 0.01 meters or approximately 0.393 inches.

centipoise (cP or cPs): A measure of dynamic viscosity; one centipoise equals 0.01 poise. Water at 70°F
has a viscosity of 1 cP.

centistokes (cSt): A unit of kinematic viscosity equal to one-hundredth of a stoke, measuring how
easily a liquid flows relative to its density.

chalk: A light, powdery residue that forms on weathered coatings or painted surfaces as the binder
degrades.

chalking: The breakdown of a coating’s binder, producing a powdery film on the surface under exposure
to sunlight and weathering.

channel flashing: A recessed flashing used where a roof meets a wall to direct runoff along an internal
trough or gutter.

checking: Small surface cracks or fine breaks in a coating that don’t extend through to underlying
layers.

chemical resistance: The ability of a material to maintain its integrity and properties when it comes
into contact with chemicals.

chimney: A vertical structure—made from masonry, stone, or metal—that houses flues to vent gases or
smoke from fires or heating systems.

chlorosulfonated polyethylene (CSPE or CSM): A synthetic rubber-like thermoset material, known
commercially as Hypalon®, commonly used for roofing membranes.

chord: A main structural element of a truss that spans from end to end and resists tension or
compression; also the straight line between two points on a curve.

cladding: The outermost layer or covering used on a building’s walls to protect from weather and
enhance appearance.

cleat: A metal strip or angled piece used to secure and anchor sheet-metal flashings or roof
panels.

clerestory: A raised section of a building wall—often with windows—that extends above the roofline to
admit additional light to the interior.

clip: A small metal fastening component used to connect panels or attach them to a substrate.

closed-cut valley: A roofing method where shingles from one slope cover the valley, and the
opposite-side shingles are trimmed back for water flow.

coal tar: A dark, heavy liquid derived from coal carbonization, used as a waterproofing or protective
roofing material.

coal-tar pitch: The waterproofing agent obtained from coal tar distillation, used in built-up roofs and
conforming to ASTM D450.

coal-tar roof cement: A thick, trowel-applied compound made from coal-tar base, fillers, and fibers for
waterproofing and repairs.

coarse orange-peel surface texture: A rough but rounded foam texture with evenly sized nodules and
valleys, acceptable for coating applications.

coated base sheet: A roofing sheet impregnated and coated with asphalt on both sides, designed to serve
as a base ply.

coated felt (sheet): A fiberglass or asphalt felt fully saturated and coated with asphalt for added
strength and weatherproofing.

coating: A liquid-applied protective layer that forms a continuous film to shield the roof or substrate
from weathering.

code: A compilation of laws or rules adopted by an authority to regulate building design, materials,
and construction practices.

coefficient of thermal expansion: The rate at which a material changes in dimension for each degree of
temperature change.

coil coating: A finishing process in which paint or coatings are applied to coiled metal in a
continuous production line before fabrication.

cold-applied: Refers to roofing or waterproofing products that can be applied without heating,
typically containing liquid carriers to achieve fluidity.

cold forming: The shaping of metal into a desired profile or cross section without using heat.

cold rolled: Steel that has been rolled into sheet form at or near room temperature to improve strength
and finish.

collar: A protective metal or flexible flashing used to seal around a vent pipe or similar roof
penetration.

color retention: The ability of a coating or finish to maintain its original color for a prolonged
period despite exposure to weather and sunlight.

color stability: The resistance of a material to fading or color changes caused by environmental
exposure.

column: A vertical structural member designed to support compression loads.

combing ridge: A decorative method of finishing the top ridge of a roof with slate or wood shingles
that extend slightly beyond the ridge line.

combustible: Capable of igniting and burning when exposed to sufficient heat.

combustion: The process of burning, characterized by rapid oxidation and the release of heat and
light.

compatible materials: Substances that can be mixed, joined, or used together without undesirable
chemical reactions or adverse effects.

composite board roof insulation: A multi-layer insulation panel combining materials such as wood fiber,
perlite, or OSB with foam insulation panels.

compound: A blended material made from a base polymer and added components such as fillers,
stabilizers, or colorants to achieve desired properties.

compression: The force that acts to shorten or squeeze a material; often measured by how much an object
is reduced in length under load.

compressive strength: The measure of a material’s capacity to resist compressive or crushing
forces.

concealed plate: See “splice plate.”

condensate: The liquid formed when vapor, such as water vapor, cools and returns to liquid
form.

condensation: The process by which vapor changes into liquid when temperature decreases or pressure
increases.

condense: To change from a gaseous state into a liquid or denser form.

conditioning: The act of storing or exposing a material specimen to particular temperature and humidity
levels prior to testing.

conductance, thermal (C): The rate of steady-state heat flow through a given thickness of material
under a temperature difference of 1°F.

conductivity (electrical): The ability of a material to allow the passage of electrical current; the
opposite of electrical resistance.

conductivity, thermal (k): The measure of the ability of a material to transmit heat through a 1-inch
thickness per 1°F temperature difference.

conductor: See “downspout.”

conductor head: A funnel-like component at the top of a downspout used to collect and direct water from
a gutter or scupper.

contamination: The presence of unwanted materials or substances that impair the performance or
cleanliness of a surface or product.

control joint: A groove or separation intentionally placed in concrete or masonry to localize cracking
caused by dimensional movement.

cool roof: A roofing surface designed with reflective and emissive materials that reduce heat
absorption and operating temperature.

coping: The cap or covering on top of a wall, parapet, or column to shed water and protect underlying
materials.

copper: A soft, corrosion-resistant metal that naturally forms a protective patina and is often used in
roofing and flashing.

core cut (core sample): A small section extracted from a roof system to identify composition, number of
layers, and condition of components.

cornice: The projecting decorative molding or trim at the top edge of a wall or under a roof
overhang.

counter-battens: Vertical wood or metal strips over which horizontal battens are mounted on steep-slope
roofs for attaching shingles or tiles.

counterflashing: A protective flashing installed over the top edge of base flashing to shield it from
exposure and water entry.

course: A single horizontal row or layer of roofing or flashing materials applied across a
surface.

coverage: The amount of surface area that a specific quantity of a material will cover under
recommended application conditions.

cover board: A rigid board installed over insulation to create a consistent surface for membrane
application or to protect underlying materials from heat.

cover plate: A flat metal strip used to cover or reinforce a joint between adjacent sheets or flashing
elements.

CPA: Copolymer alloy, a thermoplastic material used in some single-ply roof membranes.

crack: A discontinuous fracture or separation line appearing in a material due to stress or
environmental effects.

cracking: Breaks that extend through a coating or material to expose previous layers or the
substrate.

crazing: A network of fine, superficial cracks that may form on coatings, membranes, or films.

cream time: The interval after mixing polyurethane components when the material begins to expand and
change color, indicating reaction start.

creep: A slow, time-dependent deformation of a material under constant load or stress.

cricket: A small, sloped structure built into a roof to divert water away from obstructions like
chimneys or curbs.

CRREL: Acronym for Cold Regions Research and Engineering Laboratory.

crushed stone: Rock fragments mechanically broken down so that most surfaces are fractured, often used
as aggregate or ballast.

CSI: Construction Specifications Institute, an organization that develops standard construction
specifications.

CSPE: See “chlorosulfonated polyethylene.”

curb: A raised frame or structure on a roof deck used to support skylights, vents, or mechanical units
above the roof surface.

cure: The process by which a material undergoes chemical or physical change to reach its final hardened
state.

cure time: The length of time required for a material to fully reach its intended mechanical or
chemical properties.

cured concrete: Concrete that has reached its designed strength and durability after sufficient
hydration and time.

curing agent: A chemical additive used in coatings or adhesives to promote or speed up curing
reactions.

cutback: Bitumen diluted with solvent to reduce its viscosity for use as a cold-applied adhesive,
cement, or coating.

cutoff: A permanent roof system detail designed to stop lateral moisture movement within insulation
layers or membrane sections.

cutout: The slot or space between the tabs of a strip shingle, providing relief and definition.

dead level: A surface that is completely flat with no measurable slope.

dead-level asphalt: See “asphalt, dead-level.”

dead load: The weight of the permanent structural and installed building materials, excluding live
loads such as people or snow.

deck: The structural platform of a roof that provides the base surface for roofing material application
and must support expected loads.

deflection (bowing, sagging): The displacement or bending of a structural element from its original
shape when subjected to loads.

deformation: Any change in shape or dimension of a material or structure under applied stress or
force.

degradation: The reduction in physical or chemical properties of a material resulting from aging,
weathering, or other environmental exposure.

delamination: The separation or detachment of bonded layers within a laminated material or roofing
system.

dew point temperature: The temperature at which air becomes saturated and moisture begins to condense
from water vapor to liquid.

DFT: Abbreviation for dry film thickness.

diaphragm: A roof, wall, or floor element with sufficient in-plane rigidity to transfer horizontal
loads to structural supports.

differential movement: Relative displacement between connected materials caused by differences in
expansion, contraction, or loading.

diffusion: The natural movement of molecules, gases, or liquids from areas of higher concentration to
areas of lower concentration.

dimensional stability: The ability of a material to maintain its shape and size when subjected to heat
or humidity changes.

DOE: Abbreviation for U.S. Department of Energy.

dormer: A structure that projects from a sloping roof and contains a window or ventilation
opening.

double coverage: Roofing layout where each new layer overlaps the previous one enough to create two
layers of material protection.

double-lock standing seam: A metal panel seam featuring two interlocking folds that enhance water
tightness.

double tees: Precast concrete structural members with twin-stemmed cross sections used for roof or
floor systems.

downspout: A vertical pipe that carries rainwater from a gutter or scupper to the ground or lower-level
drainage system.

drag load: The lateral force applied to roofing components by heavy external loads such as snow or ice
slipping downslope.

drain: A roof component designed to collect and channel water from the surface to the drainage
system.

drainage mat: A patterned or composite material that allows water to move freely while filtering out
soil or debris in green or protected roofs.

drainage course: A material layer built into a roof system to relieve hydrostatic pressure and allow
lateral moisture flow.

drip edge: A flashing with a projecting lower lip used at roof edges to direct water away from
underlying structures.

dry: Describes a state free from moisture or the process of removing water from a material.

dry bulb temperature: The air temperature measured by a standard thermometer without any humidity
correction.

dry film thickness: The final cured thickness of a coating after all solvents or carriers have
evaporated.

dry-in (or dry-in felt): Temporary or permanent underlayment installed to make a roof watertight until
the full roofing system is complete.

drying time: The period required for solvent or water within a material to evaporate sufficiently so
that it will resist rain or dew exposure.

durability: The ability of a material or system to withstand wear, weathering, or deterioration over
time.

dynamic load: A non-static or changing load, such as wind or moving equipment, that varies with time or
force direction.

eave: The lower edge of a sloped roof that typically extends beyond the wall line.

edge venting: The inclusion of openings along a roof’s edge to permit airflow and reduce heat or
moisture buildup within the system.

efflorescence: The white, powdery deposit of soluble salts on masonry or concrete surfaces caused by
water migration and evaporation.

EIFS: Acronym for Exterior Insulation and Finish System, a nonstructural wall cladding consisting of
insulation, reinforcement, and finish coating.

EIP: Abbreviation for ethylene interpolymers, a group of thermoplastic materials used in roofing
membranes.

elasticity: The ability of a material to return to its original form after being deformed by
stress.

elastomer: A flexible polymer that can stretch significantly and recover to nearly its initial shape
when the stress is released.

elastomeric coating: A coating that can elongate substantially—often 100 percent or more—and return to
its original dimensions.

electro-galvanized: Steel coated with zinc through an electroplating process to improve corrosion
resistance.

elongation: The extent to which a material can stretch before it breaks, typically expressed as a
percentage of its original length.

embedment: The act of pressing reinforcement, plies, or granules firmly into adhesive or bitumen to
ensure full contact.

embrittlement: The loss of flexibility or elasticity in a material, often as a result of aging, extreme
cold, or UV exposure.

emissivity: The efficiency of a material’s surface in emitting absorbed heat energy as infrared
radiation.

emulsion: A stable blend of two immiscible liquids (often water and bitumen) stabilized with an
emulsifying agent for easy application.

end lap: The overlap distance created where one sheet or roll extends beyond the end of the preceding
one.

envelope (bitumen-stop): A continuous folded edge of roofing membrane sealed to prevent molten bitumen
from leaking out along the perimeter or penetrations.

EPDM: Ethylene propylene diene monomer synthetic rubber, a durable thermoset material used in
single-ply roofing membranes.

epoxy: A class of thermosetting resins that produce exceptionally hard, chemical-resistant coatings and
adhesives.

EPS: Expanded polystyrene, a lightweight closed-cell plastic foam insulation produced by molding
expanded beads.

equilibrium moisture content (EMC): The moisture level at which a material neither gains nor loses
water under stable temperature and humidity conditions.

equiviscous temperature (EVT): The temperature at which bitumen reaches the ideal viscosity for
application during roof installation.

erosion: The wearing away or gradual removal of material by mechanical or environmental forces such as
wind or water.

ethylene interpolymers (EIPs): A family of thermoplastic compounds formulated from PVC-based copolymers
for single-ply membranes.

ethylene propylene diene terpolymer (EPDM): A synthetic rubber made from ethylene, propylene, and a
diene monomer providing flexibility, weather resistance, and durability.

EVT: Abbreviation for equiviscous temperature.

expanded polystyrene (EPS): A rigid foam insulation produced by molding expanded polystyrene beads into
blocks or boards with a closed-cell structure.

expansion: The increase in size or volume of a material due to heat, moisture, or environmental
change.

expansion joint: A flexible separation between structural parts that allows movement without cracking
or damage to connected materials.

exposure: The visible or uncovered portion of a roofing component that is not overlapped by adjacent
materials.

exterior insulation and finish system (EIFS): A multi-layer wall system combining insulation,
reinforced coating, and decorative finish for exterior use.

extruded polystyrene (XPS): A rigid closed-cell foam insulation produced by continuous extrusion,
yielding smooth, dense surfaces.

extrusion: The manufacturing process where heated material is forced through a die to form continuous
shapes like sheets or tubes.

fabric: A woven or nonwoven textile used as reinforcement in membranes and flashings.

facer: A surface sheet bonded to one or both sides of insulation boards, typically made of paper, glass
mat, or metallic foil to improve strength and compatibility.

fading: The lightening or loss of intensity in a material’s color because of sunlight or weather
exposure.

fallback: A lowering of asphalt softening point or grade caused by overheating or excessive recycling
during production.

fascia: A vertical finishing board or panel located at the edge of a roof, often supporting gutters or
serving as decorative trim.

fastener: A device—such as a screw, nail, or clip—used to mechanically attach roofing or structural
materials together.

felt: A flexible sheet of interlocked fibers created with or without a binder, used as a reinforcement
or underlayment in roofing systems.

fiberboard: An insulation board made primarily from compressed cellulose fibers derived from wood or
paper.

fiberglass base sheet: A roofing base sheet reinforced with glass fibers and asphalt coating to provide
strength and stability.

fiberglass insulation: Thermal insulation composed of glass fibers, supplied as blanket or rigid board
forms.

fiberglass mat: A nonwoven web of glass fibers used to reinforce roofing membranes or shingles.

filler: An inert substance added to modify certain physical properties of compounds such as density or
flexibility.

fillet: A bead of sealant or compound installed at the corner between horizontal and vertical surfaces
to create a smooth transition.

film: A thin sheet not exceeding 10 mils in thickness, often made from plastics or coatings.

film thickness: The vertical measurement of a coating layer, expressed as wet film (as applied) or dry
film (after curing).

filter fabric: A synthetic textile that allows water flow but prevents fine materials from clogging
drainage layers.

fin: A raised, sharp ridge on a surface (often concrete) that may need removal to avoid damaging
overlying materials.

fine mineral surfacing: Inorganic granules that pass through a No. 35 sieve, used on roofing materials
to reduce stickiness and UV exposure.

fireproofing: Materials or treatments applied to structures to restrict or slow the spread of
fire.

fire rating: A classification indicating how well a material resists fire under specified testing
conditions.

fire resistance: The ability of materials or assemblies to withstand or contain fire and heat within a
defined time period.

fire-retardant-treated (FRT) plywood: Plywood infused with fire-suppressing chemicals that release
nonflammable gases when exposed to heat.

fishmouth: A half-conical opening or void formed in a lapped edge during installation, often due to
improper alignment or wrinkling.

flame spread: The rate or extent at which fire advances across a surface material.

flammable: Easily ignitable and capable of sustaining combustion rapidly.

flammability: A measure of how easily a material ignites and supports burning.

flange: The projecting edge or rim of a component, such as on flashings or fittings, used for secure
attachment or load distribution.

flash point: The lowest temperature at which vapors from a substance ignite momentarily when near an
ignition source.

flashing: Roofing accessories or materials used to prevent water penetration at joints, edges, and
rooftop transitions.

flashing cement: A heavy, trowel-applied bituminous compound formulated primarily for vertical sealing
applications.

flat lock: A method of interlocking metal roofing panels by folding adjacent sheet edges in opposing
directions and hooking them together.

fleece: A layer of fibrous matting used beneath membranes to improve bonding or provide
cushioning.

flood (pour) coat: The top layer of bitumen onto which surfacing material or gravel is embedded for
protection.

flood test: A watertightness test that temporarily holds water on a waterproofed surface for at least
24 hours to check for leaks.

flow properties: The ability of a liquid material to level naturally, forming smooth, uniform films
without defects.

fluorocarbon films: Films made from fluorine-based polymers offering exceptional chemical resistance,
color retention, and weatherability.

flute: The recessed channel between ribs in metal decking.

flux: A softening or blending material used to adjust bitumen viscosity or aid in bonding during
processing.

FM Approvals: A testing organization under FM Global that evaluates roofing materials for performance
against fire, weather, and wind uplift.

foam stop: Roof edge detail or termination used to contain spray polyurethane foam and define its
limits.

force: A physical influence that causes motion, deformation, or change within a body; measured as mass
times acceleration.

FPL: Forest Products Laboratory.

freeze-thaw cycle: The repeated freezing and melting of moisture within or on a material’s
surface.

freeze-thaw resistance: The ability of a material to withstand damage caused by repeated freezing and
thawing cycles.

friability: The tendency of a material to crumble or break apart when handled.

G-60 and G-90: Designations for galvanized sheet steel indicating zinc coating weights of 0.60 and 0.90
ounces per square foot respectively (both sides combined).

gable: The triangular upper portion of a wall that encloses the end of a pitched roof.

Galvalume®: A trade name for a corrosion-resistant alloy coating containing approximately 55% aluminum,
43.4% zinc, and 1.6% silicon applied to steel sheet.

galvanic action: The electrochemical process that occurs when two different metals come into contact in
the presence of an electrolyte, causing one to corrode.

galvanic series: A list of metals arranged according to their relative electrochemical potential in a
specific environment, used to predict corrosion behavior.

galvanized steel: Steel coated with a layer of zinc to protect it from corrosion and rusting.

gambrel: A roof design with two slopes on each side, where the lower slope is steeper than the upper,
often used in barns or traditional architecture.

gauge: A numerical designation for the thickness of sheet metal; lower numbers indicate thicker
material.

geocomposite: A prefabricated product combining fabrics or drainage materials to manage water flow and
reduce hydrostatic pressure against waterproofing systems.

geotextile: A permeable fabric used to separate, filter, reinforce, or protect materials and to allow
water passage without clogging systems.

girt: A horizontal support member that runs between wall columns to hold or support cladding
panels.

glass felt: A sheet made of glass fibers bonded with resin, commonly used for impregnation with asphalt
in roofing and waterproofing applications.

glaze coat: A final or temporary asphalt coating applied to a built-up roof membrane to seal or protect
it from weather until surfacing is added.

gloss: The measure of the shininess or reflective quality of a finished surface.

grade: Either the ground level surrounding a structure or the quality classification of a material or
product.

gradient: The rate of change in a measurable variable such as temperature or pressure per unit
distance.

graduated slate roof: A slate roof system in which slate pieces increase in thickness or length from
top to bottom to create an even appearance.

grain: A unit of weight in the imperial system equal to 1/7000th of a pound; also used to describe
natural texture in wood or other materials.

granules: Small pieces of mineral aggregate—natural or colored—used to protect and add color to asphalt
shingles and cap sheets.

gravel: Coarse rock fragments formed naturally by erosion, used in surfacing or drainage layers for
roofs and pavements.

gravel stop: A flanged edge metal used to contain loose aggregate on a roof and create a finished
perimeter appearance.

grout: A flowable mixture of cement, water, and sand used to fill gaps, joints, or cavities in masonry
construction.

gusset: A flat metal plate or series of plates placed at structural joints for reinforcement or at roof
valleys to prevent debris buildup.

gutter: A channel installed along roof edges to collect and direct rainwater to downspouts or
drains.

gypsum board panels: Flat cementitious boards composed primarily of gypsum, used as cover boards or
thermal barriers within roof assemblies.

gypsum deck: A roof deck formed by pouring a mixture of gypsum, water, and aggregate that sets into a
rigid, fire-resistant structure.

hand-tabbing: The process of manually applying asphalt adhesive to the underside of shingles to enhance
wind resistance and securement.

hardboard: A dense asphalt-impregnated protection board used in waterproofing systems, often made from
cellulosic or glass-fiber materials.

head lap: The vertical overlap distance between adjacent courses of roofing materials such as shingles
or felts.

heat flow: The transfer of thermal energy through a material or structure over time.

heat flux: The rate of heat energy flow through a surface area per unit time.

heat-fused: A method of membrane installation where the underside is melted with a torch or heater to
bond it to the substrate.

heat transfer: The process of thermal energy moving from regions of higher temperature to lower
temperature by conduction, convection, or radiation.

heat welding: The fusing together of overlapping thermoplastic sheets or materials by applying heat and
pressure to form a continuous seam.

hem: A folded edge of sheet metal that reinforces and smooths a panel or flashing.

hip: The diagonal intersection line where two roof slopes meet externally.

hip roof: A roof with slopes on all four sides meeting at a ridge or a common point, forming external
angles known as hips.

hood: A protective cover, typically metal, installed over rooftop equipment or vents to shield against
weather.

humidity: The level of moisture vapor present in the air, often expressed as relative humidity.

HVAC: Abbreviation for Heating, Ventilating, and Air Conditioning systems.

hydration: The chemical reaction in which a material like Portland cement combines with water to harden
and gain strength.

hydrocarbon: An organic compound made of hydrogen and carbon atoms, forming the basis of fuels, oils,
and bitumens.

hydrostatic pressure: The pressure exerted by a stationary fluid, such as water, at any given
depth.

hygroscopic: Describes a material’s tendency to absorb and retain moisture from the surrounding
air.

Hypalon®: A DuPont trademark for chlorosulfonated polyethylene (CSPE), a synthetic rubber material used
for durable roofing membranes.

IBC: International Building Code, a model building code that defines minimum safety requirements for
most building types.

IBHS: Insurance Institute for Business and Home Safety, an organization promoting building practices
that reduce property losses.

ICC: International Code Council, the organization that develops and maintains unified model building
codes (I-Codes®).

ice dam: A ridge of ice that forms near the edge of a cold roof when melted snow refreezes, causing
water to back up under roofing materials.

impact resistance: The capacity of a material to withstand sudden force or shock without cracking or
breaking.

impregnate: To saturate fibers or porous material with bitumen or another compound during manufacture
to increase strength and waterproofing.

incline: The slope or angle of a surface relative to the horizontal plane, often expressed as rise over
run.

inorganic: Composed of non-carbon-based materials, generally derived from minerals rather than living
organisms.

in-service R-value: The measured thermal resistance of insulation while in actual use within a building
assembly over time.

insulation: A material designed to reduce the transfer of heat between surfaces or environments,
improving energy efficiency.

interlayment: A sheet inserted between layers of roofing material (such as between wood shakes) to
improve moisture protection.

interlocking shingles: Shingles designed to fasten or lock together mechanically, improving resistance
to wind uplift without relying on seal strips.

IRC: Abbreviation for International Residential Code, governing construction of one- and two-family
dwellings and townhouses.

ISANTA: International Staple, Nail & Tool Association.

isocyanate: A reactive organic compound used as the A-component in polyurethane foams and coatings,
reacting with polyols to produce rigid or flexible polymers.

joist: A horizontal framing member—made of wood, steel, or concrete—used in rows to support floors,
ceilings, or roofs.

joule: The SI unit of work or energy equal to the work done by one newton acting through one meter of
distance.

k or k-value: See “thermal conductivity (k).”

kick-out: A short downspout or diverter added at the end of a gutter or roof-to-wall transition to
direct runoff away from the wall.

kick-out flashing (diverter): A custom metal flashing installed at the eave side of a roof-to-wall
intersection to steer water clear of the cladding.

laitance: A weak, dusty layer of fine cement and aggregate that forms on the surface of concrete due to
overworking or excess water during finishing.

laminate: To bond multiple layers of materials together, or the resulting layered product.

laminated shingles: Also called dimensional or architectural shingles, these are multiple-layered
asphalt shingles designed for enhanced strength and appearance.

lap: The overlapping portion between two adjacent roofing or waterproofing materials to ensure
watertight coverage.

lap cement: Asphalt roofing adhesive formulated to bond overlapping plies or roofing sheets.

lap seam: A seam created where one piece of material overlaps and is sealed to another of the same
type.

leaching: The process by which soluble materials are washed out of a substance, often due to water
infiltration through roofing materials.

lead: A soft, flexible metal that resists corrosion and is used in flashing, roofing, and specialty
metalwork.

leeward: The side of a building or object sheltered from the direct wind; opposite of windward.

life-cycle assessment (LCA): A method of analyzing the total environmental impact of a product or
system from creation to disposal—including material extraction, manufacturing, installation, use, and recycling.

life-cycle cost analysis: The process of evaluating all costs of a system during its life span,
including installation, maintenance, operation, and replacement expenses.

lift: A single layer or pass of spray polyurethane foam applied in one operation to achieve desired
thickness.

lightweight aggregate: See “aggregate, lightweight.”

lightweight insulating concrete fill (LWIC): A concrete mix with added air cells or lightweight
aggregates to reduce density and increase insulation value.

liquid-applied: Materials such as coatings or membranes that are applied in liquid form—by roller,
brush, or spray—and cure to form a solid waterproof layer.

liquid-applied built-up roof: A waterproofing system made from multiple alternating layers of
reinforcing fabrics and liquid adhesives, then topped with a protective coating.

live loads: Temporary or movable loads—such as people, snow, or maintenance equipment—that a roof
structure must safely support.

lot: A batch of materials grouped by production or delivery for quality control purposes; may refer to
a manufacturing or shipment batch.

low-slope roofs: Roof systems with slopes of 3:12 or less, relying on continuous waterproofing
membranes rather than shingled coverings.

low-temperature flexibility: The ability of a material to resist cracking or breaking when bent at low
temperatures.

mansard: A decorative steeply sloped roof section, often surrounding the perimeter of a building below
a flatter upper roof.

marine-grade plywood: High-quality, exterior-grade plywood made from durable veneers and waterproof
adhesives for use in moisture-prone environments.

masonry: Construction that uses units such as brick, stone, or concrete block set with mortar to create
structural or decorative walls.

mastic: A thick adhesive compound used to bond or seal roofing or waterproofing membranes.

mat: A thin layer of intertwined fibers, either woven or nonwoven, used to reinforce membranes or
provide separation between materials.

material safety data sheet (MSDS): A manufacturer-provided document outlining the chemical composition,
hazards, and safe-handling guidelines for a material.

mechanical damage: Physical harm to a roofing system caused by external impact, abrasion, or misuse
rather than normal wear and aging.

mechanically fastened membrane: A roofing membrane secured using mechanical fasteners—such as screws or
plates—through the insulation or deck.

membrane: A flexible or semi-flexible sheet material that serves as the principal waterproofing layer
in roofing or below-grade systems.

memory: The property of some materials to return to their original shape or configuration after
deformation.

metal: A generally lustrous, ductile, and conductive material used extensively for structural and
roofing applications.

metal flashing: A sheet-metal component used to seal and protect joints or transitions on roofs and
walls from water penetration.

metal rain collar: A metal counterflashing fitted around a pipe or vent penetration to prevent water
seepage into the base flashing.

metal roof panel: A large sheet of metal (typically covering at least 3 square feet) used as a roofing
surface to shed water.

meter: A metric length unit equal to 39.37 inches or 100 centimeters.

methylene diphenyl diisocyanate (MDI): The isocyanate component (A-side) used in polyurethane foam
systems to react with resin components and create polymer structures.

mil: A unit of measurement equal to one-thousandth of an inch (0.001 inch), commonly used for film
thicknesses.

mildew: A form of fungus that grows on damp organic surfaces, causing discoloration and
degradation.

mineral fiber: Insulation produced from inorganic fibers such as glass or rock wool, offering fire
resistance and sound absorption.

mineral granules: See “granules.”

mineral-surfaced roofing: Roofing materials that use mineral granules as the top protective surface
layer.

modified bitumen: See “polymer-modified bitumen.”

mold: A fungus that grows on damp or decaying organic material and can appear as staining or surface
growth.

monomer: A small molecule capable of bonding to others to form long-chain polymers.

mop and flop: A technique in bituminous roofing where roofing sheets are first coated with hot bitumen
on their underside, then flipped and pressed into place.

mopping: The method of applying hot bitumen using a mop or machine to adhere felt layers or plies in
built-up roofing.

mopping, solid: The continuous coverage of bitumen across a surface.

mopping, spot: Intermittent circular spots of bitumen applied, leaving grid-like uncoated areas between
applications.

MSDS: See “material safety data sheet.”

NAHB: National Association of Home Builders.

nailer: A wood component (sometimes called blocking) attached to a roof deck or wall to provide
anchorage for membranes, flashings, or trim.

nailing strips: Wood strips or members installed over non-nailable surfaces to allow positive
attachment of roof materials.

NBP: Acrylonitrile butadiene polymer blend used in certain proprietary roofing membranes for enhanced
flexibility and toughness.

neoprene: A synthetic rubber (polychloroprene) used in liquid or sheet form for roofing membranes and
flashing applications.

nesting: Installing new shingles or panels overlapping existing ones so that the lower edge of each new
piece aligns neatly with the old, preventing gaps or unevenness.

newton (N): The SI unit of force equal to the force required to accelerate one kilogram of mass by one
meter per second squared.

NFPA: National Fire Protection Association, an organization that develops codes and standards to reduce
fire and safety hazards.

NIST: National Institute of Standards and Technology, a U.S. federal agency that develops measurement
standards.

nitrile alloy: A flexible synthetic compound made from blended nitrile polymers, used where chemical
resistance and flexibility are needed.

NOAA: National Oceanic and Atmospheric Administration.

noble metal: A metal that resists oxidation and corrosion, such as gold or platinum, and does not
easily give up electrons.

nondestructive testing (NDT): Evaluation of a material or structure without causing damage, often used
in roofing to detect moisture or voids using infrared or electrical methods.

nonferrous metal: Any metal that does not contain significant iron and is not magnetic, such as
aluminum or copper.

nonwoven fabric: A textile in which fibers are randomly entangled or bonded by heat, chemicals, or
pressure rather than woven or knitted.

NRCA: National Roofing Contractors Association.

nylon: A strong, synthetic polyamide fiber used as reinforcement in fabric-reinforced roofing and
waterproofing membranes.

pallet: A flat platform, typically wooden, used to handle, transport, and store materials.

pan: The flat area between raised ribs on a metal roofing panel.

parapet wall: The portion of a perimeter wall that extends above the plane of the roof surface.

parting agent: A substance applied to sheet materials to prevent sticking during storage or
application; may be mineral or silicone-based.

pascal (Pa): The SI unit of pressure equal to one newton per square meter, approximately 0.2089 pounds
per square foot.

pass: A single application of spray foam or coating that produces a uniform layer after one continuous
spray motion.

paste: A thick suspension, often aluminum-based, containing metal flakes or pigment used for
coatings.

pedestal: A small base or support used to elevate and support rooftop pavers, piping, or mechanical
equipment.

peel strength: The amount of force per unit width required to peel one adhered material away from
another.

penetration: An opening or projection through a roof surface where elements such as pipes or vents
pass, often requiring flashing to seal; also the measure of consistency in bituminous materials indicating softness or
hardness.

perforated felt: A bitumen-saturated felt sheet punctured with small holes to allow venting of moisture
or gases during roofing installation.

perlite: A natural volcanic material expanded by heating, used as lightweight insulation or aggregate
in roof systems.

perm: Unit of measurement for water vapor transmission rate, representing (grains of
vapor)/(hour·ft²·in. Hg).

permeance: The rate at which water vapor passes through a material when subjected to a vapor pressure
differential.

phased application: Installing a roof or waterproofing system in separate stages or time intervals
rather than continuously.

phenolic foam: A rigid, closed-cell insulation made from phenol-formaldehyde resin, recognized for fire
resistance but may be corrosive to steel decks when wet.

pigment: A finely ground, insoluble substance added to paints and coatings to provide color and
opacity.

PIMA: Polyisocyanurate Insulation Manufacturers Association.

pinhole: A very small hole or defect in a film or membrane that can allow moisture leakage.

pitch: See “coal tar” or “roof slope.”

pitch-pocket (pitch-pan): A metal, open-bottomed enclosure around a roof penetration filled with
sealant or grout to waterproof the area.

plastic cement: A trowel-grade asphalt-based sealant formulated for low-slope applications but not
vertical ones.

plasticizer: An additive—liquid or solid—introduced into polymers to increase flexibility and reduce
brittleness.

plasticizer migration: The gradual movement or loss of plasticizers from a thermoplastic membrane,
leading to shrinkage or hardening over time.

pliability: The ease with which a material can bend or flex without cracking or breaking.

ply: A single sheet or layer of felt or reinforcement material used in a multi-layer roof
system.

plywood: A rigid panel consisting of multiple layers of wood veneers glued with alternating grain
directions for strength and dimensional stability.

PMR: See “protected membrane roof (PMR).”

polyester: A polymer resin in which the molecular chain contains ester groups; used as reinforcement
fabric in roofing materials.

polyisobutylene (PIB): A synthetic rubber derived from isobutylene monomers, used for flexible,
impermeable membranes.

polyisocyanurate foam: A closed-cell rigid insulation made from reacting polyisocyanates with
polyhydroxyl compounds, yielding high thermal resistance.

polyisocyanurate foam board: Rigid thermal insulation consisting of polyisocyanurate foam sandwiched
between facer sheets; often referred to as “iso board.”

polymer: A large molecule made up of repeating smaller units (monomers), formed through chemical
reactions such as polymerization.

polymer-modified bitumen: Bitumen improved with added polymers, such as SBS or APP, to increase
flexibility and temperature resistance.

polymeric methylene diphenyl diisocyanate (PMDI): A variant of MDI used as the reactive component in
polyurethanes and spray foam insulation.

polymerization: The chemical process of linking monomers together to create polymers with specific
properties.

polyol: A compound containing multiple hydroxyl groups, used as the reactive B-component in
polyurethane foams and coatings.

polypropylene: A thermoplastic polymer made by polymerizing propylene, valued for its durability and
resistance to chemicals.

polyurethane: A synthetic polymer produced by a chemical reaction between an isocyanate and a polyol,
resulting in solid, flexible, or foam materials.

polyurethane foam (cellular polyurethane): A rigid insulation created by spraying a mixture of
isocyanate and resin, forming a closed-cell foam that adheres tightly to surfaces.

polyurethane coating: A one- or two-part solvent-based coating that cures through chemical reaction to
form a durable, flexible film.

polyvinyl chloride (PVC): A synthetic thermoplastic polymer derived from vinyl chloride, available in
rigid and flexible forms for roofing membranes and pipes.

polyvinylidene fluoride (PVDF): A thermoplastic fluoropolymer used in high-performance architectural
coatings for its superior color retention and weather resistance.

polystyrene: A rigid plastic resin formed by polymerizing styrene monomers, used to create lightweight
insulation boards.

ponding: The prolonged collection of water in roof depressions that fails to drain within 48 hours
after precipitation under drying conditions.

popcorn surface texture: In spray polyurethane foam (SPF) roofing, a very coarse texture with sharp
valleys and peaks that is unsuitable for direct coating without reworking.

Portland cement: A hydraulic cement made from ground limestone and clay that reacts with water to
harden and gain strength.

positive drainage: Roof design ensuring that accumulated water drains from the surface within 48 hours
under drying conditions.

pot life (working life): The time span after mixing reactive components during which the product
remains workable before curing begins.

pour coat: See “flood (pour) coat.”

pourable sealer: A fluid, often two-part sealant, used in penetration pockets or difficult-to-flash
roof areas to create watertight seals.

pressure-sensitive: Describes adhesives that stick firmly to surfaces once pressure is applied, without
heat or solvent activation.

pre-stressed concrete: Concrete reinforced with tensioned cables or rods before loading, enhancing
compressive strength under structural loads.

pre-tinning: The process of coating a metal surface with a thin solder or tin layer before joining by
soldering or brazing.

primary drainage: The main roof drains or scuppers that remove rainwater directly from the roof
surface.

primer: A thin, low-viscosity coating applied to a surface to promote adhesion or prepare it for
subsequent layers.

protected membrane roof (PMR): A roof design where insulation and ballast are installed above the
waterproof membrane, shielding it from temperature extremes and damage.

protection course: A sacrificial material layer placed over waterproofing membranes to protect them
from construction traffic or mechanical damage.

protection mat: A cushioning layer placed between roof components to prevent abrasion or mechanical
wear.

psi: Abbreviation for pounds per square inch, a unit of pressure or stress.

psychrometric chart: A graph showing relationships among air temperature, humidity, dew point, and
moisture content used in HVAC and building analysis.

puncture resistance: The capacity of a membrane or insulation to resist being pierced by a sharp
object.

purlin: A horizontal secondary framing member spanning between main structural supports, used to
support roofing panels.

PVC: See “polyvinyl chloride (PVC).”

PVDF: See “polyvinylidene fluoride (PVDF).”

R-value: See “thermal resistance (R).”

racking: A shingle installation method laying courses vertically up the roof rather than horizontally,
producing a staggered pattern.

rafter: A sloping beam that extends from a ridge down to an eave or wall plate, supporting the roof
deck or sheathing.

raggle: A groove cut into masonry or a similar surface for inserting and securing flashing.

rake: The inclined edge of a roof running from the eave to the ridge, forming the end of a sloped
section.

RCI: Roof Consultants Institute, formerly RCI Inc.—now called the International Institute of Building
Enclosure Consultants (IIBEC).

RCMA: Roof Coatings Manufacturers Association.

receiver: The fixed section of a two-part counterflashing designed to allow easy installation or future
maintenance without disturbing wall finishes.

re-covering: Installing a new roof membrane or covering over an existing roof without removing old
materials.

reflectance: The fraction of incident solar energy reflected by a surface, expressed as a decimal or
percentage.

reflectivity: The inherent property of a material that defines its ability to reflect radiant energy,
independent of surface condition.

reglet: A metal or formed channel used as a receiver for counterflashing, installed in or behind
masonry or wall cladding.

reinforced membrane: A roofing or waterproofing membrane made stronger by incorporating fabrics such as
fiberglass, polyester mesh, or scrim.

relative humidity (RH): The ratio of the actual amount of water vapor in the air to the maximum it can
hold at a given temperature, expressed as a percentage.

replacement: The complete removal of an existing roof covering, repair of damaged substrates, and
installation of a new roof system.

reroofing: Either re-covering or replacing an existing roof covering; may include repair of underlying
materials.

resin: The B-component in polyurethane foam systems containing polyols, blowing agents, and catalysts;
more generally, a base polymer for plastics or adhesives.

retrofit: Modifying an existing building system by upgrading or adding modern components without full
reconstruction.

ridge: The top horizontal line of a sloped roof where two opposing slopes intersect.

ridge board: A horizontal board at the top of a roof frame where rafters are attached; serves as a
structural alignment reference.

ridge cap: Shingles, tiles, or other materials installed over the ridge to protect and cover the joint
between roof planes.

ridge course: The topmost row of shingles, slate, or tile used to cover the ridge on sloped
roofs.

ridge vent: A linear vent located at the roof ridge that allows warm, moist air to escape from attic
spaces.

ridging: See “buckle.”

roll materials: General term for roofing sheets or felts that are supplied in rolls for ease of
handling and installation.

roll roofing: Asphalt-impregnated felt or mineral-surfaced sheet supplied in rolls for low-cost roofing
applications.

roof: The upper covering of a building that provides shelter from weather; also used as a verb meaning
to install roofing material.

roof area divider: See “area divider.”

roof assembly: The complete combination of roof components—including deck, insulation, and
membrane—working together to weatherproof the structure.

roof cement: See “asphalt roof cement” and “coal-tar roof cement.”

roof covering: The exposed, outermost roofing material such as shingles, membrane, or metal
panels.

roof curb: A raised frame used to mount and support roof penetrations or equipment like fans, HVAC
units, or skylights.

roof overhang: The roof section projecting beyond exterior walls to provide shading and direct runoff
away from the building.

roof slope: The angle or rise-to-run ratio of a roof surface, indicating the steepness of the
pitch.

roof system: The total combination of interacting roofing elements, such as the membrane, insulation,
and flashing, designed to resist weather and improve insulation.

rosin paper: Non-asphaltic sheathing paper used as a separating layer or slip sheet in roofing
assemblies.

rubber: A natural or synthetic elastic material capable of high stretch and recovery; used in various
roofing membranes.

run: The horizontal distance corresponding to the rise in a roof’s slope measurement.

rust: A reddish or brownish corrosion product that forms on iron or steel when exposed to moisture and
oxygen.

sacrificial protection: A method of corrosion prevention where one metal corrodes preferentially to
protect another (as in galvanic coatings).

saddle: A small, sloped roof structure that directs water around an obstacle, such as a chimney, to
improve drainage.

saturant: A bituminous liquid used to impregnate dry felts in the manufacture of saturated roofing
sheets.

saturated felt: Felt that has absorbed as much bitumen as it can during processing but remains porous
and flexible.

SBS: Styrene-butadiene-styrene, a thermoplastic elastomer used to modify bitumen for greater
flexibility and durability.

scarfing: In spray polyurethane foam roofing, the act of grinding or trimming high foam areas to
achieve a level surface.

screeding: The process of striking off excess concrete to create a flat, level finish at the correct
elevation.

scrim: A woven or nonwoven mesh fabric used to reinforce membranes or coatings.

scupper: An opening through a parapet or roof edge that allows water to drain through to an exterior
downspout or gutter.

scuttle: A roof hatch or opening providing access to the roof from the building interior.

SDI: Steel Deck Institute, an organization that establishes standards for steel decks.

sealant: A pliable material with both adhesive and cohesive properties used to fill joints and create a
long-lasting, flexible seal against air and water infiltration.

sealant foam: A one- or two-component expanding polyurethane foam applied to joints and transitions to
control air leakage and improve insulation continuity.

sealer: A thin coating designed to reduce porosity, control absorption, or prevent color bleed on a
substrate prior to finish coating.

seam: A joint between adjoining sheets or materials; may be made watertight through welding, adhesives,
sealant, or mechanical fastening.

secondary drainage: Also called “overflow drainage”; supplemental drains or scuppers that provide
backup water removal if primary drains become blocked.

self-adhering membrane: A roofing or waterproofing membrane with a built-in adhesive layer protected by
a release film, which bonds under applied pressure without added adhesives.

self-adhering: Describes materials that adhere upon contact and pressure, without requiring external
activation such as heat or solvents.

self-drying roof assembly: A low-slope roof designed to allow limited moisture entry and facilitate
drying through vapor movement without performance issues.

self-flashing: The capability of a membrane or material to wrap around penetrations or transitions
without separate flashing components.

self-healing: The ability of some bituminous materials to soften with heat and flow to seal minor
cracks automatically.

self-tapping screw: A threaded fastener that forms its own threads as it is driven into a predrilled
hole.

selvage: The differently treated or defined edge of a roll material designed for overlapping or seaming
adjacent courses.

separator layer: See “slip sheet.”

service life: The expected time during which a material or system performs effectively under normal
maintenance conditions.

shading: Slight variations in surface color among roofing products that do not affect performance but
may influence appearance.

shear strength: The ability of a material to resist sliding failure when forces are applied parallel to
its surface.

shelf life: The maximum recommended storage period during which a product remains usable under proper
conditions.

shingle: A small, individual roofing unit installed in overlapping rows to shed water; may be asphalt,
wood, slate, or metal.

shrinkage: The dimensional contraction of a material due to curing, drying, or environmental
changes.

SI: Abbreviation for the International System of Units (Système International).

side lap: The overlapping longitudinal joint between two adjacent roofing or wall panels.

side-lap fastener: A screw, rivet, or other mechanical device used to connect neighboring panels along
their side laps.

siding: The exterior cladding material—such as wood, vinyl, or metal—applied to the outer walls of a
framed building.

sieve: A mesh device used for separating granular material into various particle sizes.

silicone coating: A liquid-applied elastomeric coating made primarily from silicone resins, providing
UV and water resistance for roof protection.

single-component (coating or foam): A product that does not require mixing prior to use, curing through
moisture or chemical reaction with air.

single-ply membranes: Flexible roof membranes applied in a single layer rather than multiple plies,
available in thermoset or thermoplastic formulations.

single-ply roofing: A roofing system consisting of one primary layer of waterproof membrane directly
applied to insulation or substrate.

single tees: Precast, prestressed concrete members with a T-shaped cross-section used in decking for
roofs or floors.

SJI: Steel Joist Institute, a group that establishes standards and load tables for open-web steel
joists.

skin: The dense or hardened outer layer formed on a liquid coating, mastic, or foam due to exposure to
air or curing.

skinning: The formation of a cured surface film on coatings or sealants as they begin to dry or react
with air.

skylight: A roof opening covered with glass or translucent plastic material to admit daylight into
interior spaces.

slag: A glassy by-product produced during metal smelting; often used as an aggregate or surface
material for roofing systems.

slate: A fine-grained metamorphic rock used for durable and long-lasting steep-slope roofing
tiles.

slip sheet: A film or thin sheet placed between components of a roof system to prevent adhesion or
abrasion due to movement; also called a separator layer.

slippage: Lateral movement between roofing plies or layers, commonly caused by gravity or thermal
stress on sloped surfaces.

slit sample: A small cut in spray polyurethane foam used to measure coating thickness and adhesion
between layers.

slope: The ratio of vertical rise to horizontal run that indicates a roof’s degree of incline.

SMACNA: Sheet Metal and Air Conditioning Contractors’ National Association, which sets standards for
sheet-metal fabrication and installation.

smooth surface texture: In SPF roofing, a surface with minor undulations suitable for receiving a
uniform protective coating.

smooth-surfaced roof: A roof membrane system with a plain exposed weather surface free of granules or
aggregate.

Snap-On cap: A separate metal piece that snaps over the raised seam of certain standing- or batten-seam
roofing panels for a finished appearance and water tightness.

snow guard: A device or series of devices installed on sloped roofs to hold snow in place and prevent
dangerous sliding.

snow load: The vertical load on a roof created by the weight of accumulated snow, expressed in pounds
per square foot.

soffit: The underside surface of a roof overhang or eave.

soffit vent: An intake vent located at or near the eave that allows air to flow into attic or rafter
spaces for ventilation.

softening point: The temperature at which a bituminous material becomes sufficiently soft to begin
flowing under specified conditions.

soil stack: A vertical pipe that carries wastewater and vent gases through the roof from plumbing
fixtures.

solder: A fusible metal alloy, typically of lead and tin, used to bond metal pieces together by melting
and cooling.

solids content: The percentage of a coating, adhesive, or compound that remains as a solid film after
solvent or water evaporation.

solubility: The degree to which a substance can dissolve in a given solvent under specific
conditions.

solvent: A liquid capable of dissolving another substance to form a uniform solution, used in coatings
or adhesives.

solvent welding: A process where solvent softens thermoplastic materials so that adjoining surfaces
fuse together as the solvent evaporates.

spalling: The breaking or chipping off of surface layers from materials such as concrete or masonry,
often due to freeze–thaw cycles or corrosion.

span: The horizontal distance between two supports that a structural member bridges.

spangle: The visible crystalline pattern that appears on the surface of hot-dipped galvanized coatings
when they solidify.

special steep asphalt: See “asphalt, special steep.”

specification: A formal document that precisely defines materials, performance, and methods required
for construction or fabrication.

SPF: Spray polyurethane foam, a foamed plastic insulating and roofing material created by combining
isocyanate and resin components.

SPFA: Spray Polyurethane Foam Alliance, an industry trade association representing SPF contractors,
manufacturers, and suppliers.

SPF compound: The base components—typically isocyanate and resin—used together to produce spray
polyurethane foam.

splice: The joint formed when two overlapping materials are bonded, welded, or otherwise joined
together.

splice plate: A flat metal plate placed below joints between two metal components to provide support
and continuity.

splice-tape: A rubber or polymer tape used to seal or join the seams of membrane roofing
materials.

split: A tear or rupture in a membrane or material, usually caused by tensile stress or
movement.

spot mopping: See “mopping, spot.”

spray polyurethane foam (SPF): A foam plastic system created by spraying a reactive mix of isocyanate
and polyol, forming a rigid, seamless insulation and waterproofing layer.

SPRI: Single-Ply Roofing Industry, a trade organization focused on single-ply roofing system
standards.

sprinkle mopping: A bituminous application method in which hot bitumen is splashed in small droplets
instead of a solid coat.

square: A roofing measurement equal to 100 square feet of roof area, also referring to the amount of
material required to cover that area.

squeegee: A rubber or plastic-edged tool used to spread or remove liquids; also the act of smoothing a
coating or membrane using such a tool.

staining: The discoloration of roofing materials due to contact with contaminants, water, or biological
growth.

stainless steel: Steel alloyed with chromium (and sometimes nickel) for superior corrosion resistance
and durability.

standing seam: A roofing seam created by raising and folding adjoining metal panel edges vertically to
form a watertight joint.

starter course: The initial layer of roofing material installed along the eave or base line to ensure
proper sealing and coverage by succeeding courses.

starter sheet: A narrow-cut membrane or felt strip used to begin a roofing pattern or form perimeter
strips in single-ply membrane installations.

starter strip: Roofing or shingle pieces laid along the eave before applying the first full course,
filling the gaps between tabs and improving seal at the edge.

steel: An iron-carbon alloy containing small amounts of other elements, known for toughness, strength,
and ductility; widely used structurally and decoratively.

steel joist (open web steel joist): Prefabricated steel truss members used as horizontal supports for
roof or floor decks.

steep asphalt: See “asphalt, steep.”

steep-slope roofs: Roofs with a gradient over 3:12 that rely on overlapping materials to quickly shed
water rather than seal against it.

step flashing: Small, overlapping metal flashing pieces installed in a stepped pattern along
roof-to-wall intersections.

strapping (felts): The installation method where roll materials are laid parallel to the roof’s slope
rather than across it.

stress: The internal resistance developed inside a material when external forces are applied, often
measured in force per unit area.

strip flashing: Narrow membrane strips used to secure metal flanges or joints into a roof
membrane.

strip shingles: Asphalt shingles produced in long strips, typically three times as wide as they are
tall, with or without cutouts.

stripping in: Applying strips of membrane over flashings or joints to reinforce and seal them.

structural panel: A metal roof panel strong enough to be installed over open framing rather than
continuous decking.

styrene butadiene styrene copolymer (SBS): A high-performance elastomer that improves bitumen’s
flexibility and elasticity, used in modified bitumen roofing.

substrate: The base surface—such as a deck or insulation layer—on which roofing materials are
applied.

sump: A slightly recessed area around a roof drain designed to promote water flow toward the
outlet.

sump pan: A metal plate or pan installed to create the depression around a roof drain for improved
drainage.

surface texture: The visual or physical texture of a surface, especially in spray polyurethane foam
finishes, ranging from smooth to rough types.

surfacing: The outermost protective layer of a roofing system, designed to resist UV exposure, impact,
and weathering.

synthetic rubber: Any man-made elastomeric material similar to natural rubber, used in roofing
membranes for flexibility and strength.

tab: The individual exposed section of a strip shingle, typically defined by cutouts separating
adjacent tabs.

tack-free time: In spray polyurethane foam application, the interval after spraying when the surface
loses tackiness and can be recoated or walked on.

talc: A fine, white powder applied to membranes to prevent sticking during handling and
storage.

tapered insulation: Insulation panels precut or molded to create slope on flat roofs, directing water
toward drains.

taping: The process of sealing insulation or deck joints, or joining single-ply membranes, using tapes
or adhesive strips.

tar: A dark, viscous bituminous substance obtained from the distillation of organic materials like coal
or wood, used for waterproofing.

tear resistance: The material’s ability to resist tearing when subjected to a concentrated force on a
small area.

tear strength: The maximum force required to tear a specimen under specified testing
conditions.

tensile strength: The maximum tension a material can endure before breaking, measured as force per
cross-sectional area.

termination: The method of sealing or anchoring the free edge of a roofing membrane to prevent peeling
or moisture intrusion.

terne: A tin-zinc alloy coating applied to carbon-steel sheets for improved corrosion resistance,
previously made from lead-tin compositions.

test cut: See “core cut.”

test method: A defined procedure for measuring or evaluating specific characteristics or properties of
materials to ensure compliance with standards.

textural slate roof system: A slate installation using pieces of mixed thickness or texture for a more
varied, natural appearance.

thermal barrier: A non-combustible layer installed beneath torched or heated membrane applications over
flammable substrates to prevent fire risk.

thermal conductance (C): The rate of heat transfer through a given material thickness induced by a
one-degree temperature difference.

thermal conductivity (k): The amount of heat that flows through one inch of material per hour under a
one-degree temperature difference.

thermal cycling: Repeated temperature changes causing alternating material expansion and contraction
stresses.

thermal expansion: The increase in dimensional size of a material caused by rising temperature.

thermal insulation: A material used to slow heat transfer to maintain desired indoor temperatures and
conserve energy.

thermal movement: Dimensional changes in a material resulting from temperature variations.

thermal resistance (R): The measure of a material’s ability to resist heat flow; the reciprocal of
thermal conductance (C).

thermal resistance ratio (TRR): The ratio comparing a material’s wet thermal resistance to its dry
performance under specified conditions.

thermal shock: Stress generated within a material when it experiences a rapid temperature change, such
as sudden cooling after heating.

thermal stress: Internal forces produced in a material when its expansion or contraction is restrained
due to temperature variation.

thermal transmittance (U or U-factor): The overall heat flow rate through a building component,
including all layers and air films, expressed as Btu/hour·ft²·°F.

thermoplastic: A material that softens when heated and hardens upon cooling, a process that can be
repeated without major degradation.

thermoplastic elastomer: A polymer material that behaves like rubber but can be repeatedly softened by
heat and hardened by cooling.

thermoplastic olefin membrane (TPO): A single-ply roofing membrane made from a blend of polypropylene
and ethylene-propylene rubber with UV stabilizers and other additives.

thermoset: A class of polymers that undergo permanent chemical reactions during curing, becoming hard
and infusible even when reheated.

thinner: A volatile liquid used to adjust viscosity of adhesives or coatings or to clean application
tools.

through-wall flashing: Flashing that extends completely through a masonry or framed wall to direct
internal water to the exterior through weep holes.

tie-in (tie-off): The junction where a new roofing or waterproofing section transitions and seals to an
existing one to ensure continuous waterproofing.

T-joint: The overlap point where three or four sheets of membrane intersect at a single
location.

toggle bolt: A screw with spring-loaded wings that expand behind a hollow wall to provide secure
fastening from one accessible side.

tongue-and-groove planks: Wooden planks with interlocking edges that fit together for tight, flush
joints commonly used in decking.

torch-applied: A method for installing modified-bitumen roofing by heating the sheet underside with an
open flame to melt and bond it to the substrate.

TPO: See “thermoplastic olefin membrane (TPO).”

treebark surface texture: A rough, irregular spray polyurethane foam texture with sharp angular
valleys, unsuitable for direct coating without additional smoothing.

TRI: Tile Roofing Industry, an organization representing manufacturers of roof tiles and related
products.

truss: A framework composed of triangular units that distribute loads and support roofs or bridges
efficiently using tension and compression members.

two-component system: A material (such as SPF or coatings) formed by mixing two different components
that react chemically to cure.

UL: See “Underwriters Laboratories Inc. (UL).”

UL label: Certification marking by Underwriters Laboratories indicating that a product has been tested
and meets safety or performance standards.

ultraviolet (UV): Invisible radiation just beyond the violet end of the visible light spectrum, with
wavelengths from about 400 to 100 nanometers, capable of degrading exposed materials.

underlayment: A sheet material, often asphalt-saturated or self-adhering, placed between the roof deck
and outer covering to add secondary water resistance.

Underwriters Laboratories Inc. (UL): An independent organization that tests and certifies product
safety and performance for consumer and industrial use.

unforeseen conditions: Site or construction issues not reasonably predictable from contract documents,
differing significantly from expected conditions.

uplift: The negative pressure or suction on a roof caused by wind currents that can lift material edges
or components.

urethane: See “polyurethane.”

UV degradation: Deterioration or breakdown of materials due to prolonged exposure to ultraviolet
radiation from sunlight.

valley: The internal angle formed where two sloping roof planes intersect, directing water to gutters
or drains.

vapor barrier: See “vapor retarder.”

vapor diffusion: The natural migration of water vapor molecules through materials from areas of higher
vapor pressure to lower pressure.

vapor migration: The movement of water vapor driven by vapor pressure differences within building
assemblies.

vapor pressure: The pressure exerted by a water vapor at a specific temperature; part of the total
atmospheric pressure.

vapor retarder: A material or assembly that limits water vapor passage under defined conditions,
reducing condensation potential within building envelopes.

vapor retarder class: The classification of vapor retarders based on permeance: Class I (≤0.1 perm),
Class II (0.1–1.0 perm), and Class III (1.0–10 perm) per ASTM E96.

vent: An opening designed to allow air, vapor, or gas to escape from the building to the
outdoors.

verge-of-popcorn texture: In spray polyurethane foam roofing, a rough surface exhibiting large nodules
and partially cured valleys; acceptable for coating but inefficient due to extra coating requirement.

vermiculite: A lightweight, expanded aggregate used in insulating concrete and soil mixtures.

viscosity: A measure of a fluid’s resistance to flow; higher values indicate thicker, slower-moving
materials.

viscous: Having a high resistance to flow under stress, characteristic of thick liquids like
bitumen.

void: A hollow space, gap, or air pocket within a material that can affect strength or
performance.

volatile: Describes substances that readily vaporize at normal temperatures, such as solvents.

waffle slab: A reinforced concrete deck system featuring a grid of ribs resembling a waffle pattern,
providing strength with reduced weight.

walkways: Designated roof paths or surface protection areas used to prevent damage from foot traffic or
maintenance activities.

wash coat: A thin primer applied to the back of coated metal panels to prevent corrosion or surface
wear.

water cutoff: See “cutoff.”

water-shedding: The ability of overlapping building components to repel and direct water without
depending on pressure resistance.

water-shedding roof system: A steep-slope roof system that relies primarily on gravity-driven drainage
to keep water from entering the structure.

water and ice-dam protection membrane: A waterproof underlayment installed beneath steep-slope roof
coverings in cold climates to prevent leaks caused by ice damming or wind-driven rain.

water testing: Controlled testing—either flood or flowing-water—used to verify the watertight integrity
of a waterproofing system.

water vapor pressure: The portion of total atmospheric pressure due specifically to the presence of
water vapor in the air.

water vapor retarder: See “vapor retarder.”

water vapor transmission: The rate at which water vapor passes through a material under standardized
testing conditions.

waterproof: The quality of a membrane or material that completely prevents the passage of water under
hydrostatic pressure.

waterproofing: Methods or treatments applied to a surface or system to prevent water infiltration even
under pressure.

waterproofing assembly: A collection of components—including membranes, protection, and drainage
materials—working together to exclude water from a structure.

waterproofing membrane: The primary component of a waterproofing system specifically designed to block
liquid water penetration.

waterproofing system: A complete combination of waterproofing membranes, sealants, drains, and
protection layers integrated to prevent water intrusion.

waterstop: A flexible barrier installed across concrete joints to seal against water movement through
the joint.

weatherproof: Resistant to weather effects and capable of preventing water entry under limited pressure
exposure.

weld: To permanently fuse two materials together using heat, pressure, or a chemical reaction.

wet: In a condition containing visible moisture or liquid water; also refers to freshly applied
coatings prior to curing.

wet film gauge: A measurement tool used to determine the thickness of a coating immediately after
application before it dries or cures.

wet film thickness: The measured thickness of a coating in its liquid, uncured state.

wicking: The upward or horizontal movement of moisture through small openings or pores via capillary
action.

wind screen: A device used around spray application zones (like spray foam) to control drift or loss
caused by air movement.

wind uplift: The upward or lifting pressure on roofing materials caused by wind across roof surfaces or
edges.

woven valley: A shingle valley installation where each side’s courses overlap or interweave as they
cross the valley line for improved water shedding.

yield: The volume output of foam material per unit of weight—commonly measured in board feet per pound
of polyurethane.

zinc: A bluish-white metal that forms a protective carbonate film when exposed to air, providing
self-healing corrosion resistance and widely used as a galvanizing coating.