Roofing Terms

AbsorptionThe ability of a porous, solid material to hold a relatively large quantity of liquid (or gas).
AdhesionMeasured in shear and peel modes, this is the state in which two surfaces are held togegther by interfacial forces. These forces may consist of molecular forces, interlocking action, or both.
Adhesive FailureThis is the separation of two bonded surfaces which occur at the interface between the adhesive and the material being bonded.
AggregateThis is often crushed stone, slag, or water-worn gravel used for surfacing a built-up roof. It can also refer to any granular mineral material.
AgingThis is the effect environmental exposure has on a material after an interval of time. It also refers to the process of exposing materials to environmental conditions for a period of time.
AlligatoringThis term refers to the shrinkage and/or cracking of the surfacing bitumen on a built-up roof. The result resembles an alligator’s hide. The cracks may or may not extend through the entire surfacing bitumen thickness.
ANSI American National Standards Institute
AntidegradantThis is a compounding material used to attempt to retard deterioration caused by oxidation, ozone, light, and/or a combination of these. It can also be used as a generic term for additives like antioxidants, antiozonants, and waxes
AntioxidantA substance designed to prevent or retard oxidation of material exposed to air
Approval drawingsThese are drawings, which may include framing drawings, elevations, or building sections, furnished by the manufacturer for approval of the buyer. Approval by the buyer signifies the manufacturer has correctly interpreted the overall contract requirements for the system and its accessories, and the exact location of these.
Architectural drawingA drawing that shows the plan view and/or elevations of the finished building to show the feneral appearance of the building and indicates all accessory locations.
AsbestosA group of natural fibrous impure silicate materials.
AsphaltA dark brown to black cementitious material whose predominating constituents are bitumens occuring in nature, or are created through petroleum processing.
Asphalt feltFelt saturated with asphalt.
Asphalt, air blownAir is blown through asphalt to raise softening point and modify other properties.
Asphalt, roof cementThis is a trowelable mixture of asphalt, mineral stabilizers, fillers, and/or other fibers.
Asphalt, steam blownSimilar to air blown asphalt, steam is blown through molten asphalt to modify properties.
ASTMAmerican Society for Testing and Materials
AWSAmerican Welding Society
Backup plateA rigid plate designed to support an end lap in a metal panel roof. This is to provide uniform compression.
BallastLoose aggregate, concrete pavers, or other material used to prevent wind uplift or flotation of a loose-laid roof system.
Barrier protectionA physical, inert barrier used as protection from the environment. If the barrier is broken, the underlying base metal is unprotected.
Base sheetA saturated or coated felt used as the first ply in a multi-ply bituminous roofing membrane.
BattenA raised rib in a metal roof. This can also be used to describe separate part or a formed portion in a metal roofing panel.
Bill of materials (BOM)A list of items or components used for fabrication, shipping, receiving, and accounting purposes.
BitumenThis is most often used to describe a class of amorphouse, black or dark colored, cementitous substances, either natural or manufactured, composed principally of high-molecular-weight-hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars, pitches, and asphaltites. Bitumen is also used as a generic term for any material composed mainly of bitumen.
BituminousA material containing or treated with bitumen.
Bituminous emulsionThe suspension of small globules of bituminous material in water or another aqueous solution.
Blanket insulationFiberglass insulation in a roll form. This is frequently installed between metal roof panels and the supporting purlins.
BlisterThis is a raised portion of a roof membrane caused by interal pressure in an air-water-vapor pocket trapped between either the membrane and its substrates or between membrane layers.
Blister – polyurethane foamAn undesirable rounded delamination of the surface of polyurethane foam. The boundaries may or may not be sharply defined.
BOCABuilding Officials and Code Administration
BondAdhesive and cohesive forces holding two components in intimate contact.
BootThis is a bellows-like covering to exclude dust, dirt, moisture, etc., and forms a flexible closure.
Builder/ContractorA general contractor or subcontractor responsible for providing and erecting building systems.
Building codePublished regulations and ordinaces describing design loads, procedures, and construction details for structures, established by a recognized agency.This usually controls design, construction, material quality, use and occupancy, location, and maintenance for a specific area.
Built-up roofing (BUR)A continuous semiflexible membrane consisting of plies of saturated felts, coated felts, fabrics, or mats, which are assembled in place with alternate layers of bitumen. This is surfaced with mineral aggregate, bituminous material, or a granule surfaced sheet.
BullA roofer’s term used for flashing or plastic cement.
Butyl rubberA synthetic rubber based on isobutylene and a minute amount of isoprene. Vulcanizable, this features a low permeability to gasses and water vapor. It is also relatively resistant to aging, chemicals, and weathering.
CanopyAny overhang from the roof – usually with an unsupported end.
Cap sheetA granule-surfaced coated felt used as the top ply of a built-up or modified bituminous roofing membrane.
CaulkTo seal joints, seams, or voids through filling the area with a waterproofing compound or material.
CaulkingA composition made of vehicle and pigment that is used at ambient temperatures for filling joints. Caulk remains plastic for an extended period of time after application.
Cavity wallA wall built of hollow masonry units which are arranged to provide a continuous internal air space.
Coal tarA dark bown to black cement-like material which is produced through destructive distillation of coal.
Coal tar feltA felt that is saturated with refined coal tar.
Coal tar pitchA dark brown or black, solid cement-like substance that is obtained as a residue from the partial distillation or evaporation of coal tar.
Coated fabricA fabric coated with a plastic solution, dispersion hot melt, or powder.
Coated sheet or feltAn asphalt felt which has been coated on both sides with a more viscous asphalt or a glass-fiber felt that has been impregnated and coated with asphalt on both sides.
Coating weightThis is the weight of a surface coating, usually expressed in ounces per square foot (or grams per square meter).
Collector boxThis is the transition piece between a gutter and a downspout. It is designed to facilitate water flow.
CondensationPart of the conversion of water vapor to a liquid state as the temperature cools or there is a rise in atmospheric pressure.
Conductivity – electricalThe reciprocal of electrical resistance.
Cool Roof Rating Council (CRRC)The council establied to provide radiative data on roof surfaces to the building industry.
CopingA covering on top of an exposed wall. This is usually sloped for water drainage.
CounterflashingMade of formed metal or elastomeric sheeting, this piece is secured on or into a wall, curb, pipe, rooftop unit, or other penetration, to shield the upper edge of a base flashing and it’s fasteners from the weather.
CricketThis is generally a small elevated area of a roof which is contructed to divert water from a horizontal intersection of the roof with a projection such as a chimney, wall, or expansion joint.
CurbA raised area used for support of roof penetrations such as skylights and hatches.
CureThe process of using heat, radiation, or reaction with chemical additives to change the properties of a polymeric system into a more usable compound.
Curled feltA defect of a built-up roof (BUR) membrane. This is charaterized by a continuous, open longitudinal seal where the top felt is rolled back from the bottom felt.
Dead-levelZero slope.
DeckThis is the structural surface to which the roofing system is attached.
DelaminationSeparation of the piles in a membrane or separation of insulation layers after lamination.
DownspoutThis is a conduit used to move water from the gutter to the ground or storm drain.
Duck-boardSlatted flooring laid on a wed, muddy, or cold surface.
EaveThe line formed along a sidewall by the intersection of planes of the roof and wall.
Edge strippingThis is the application of felt strips cut to narrower widths than the normal felt roll width used to dover a joint between a flashing a a bituminous roof.
Edge ventingThis refers to the practice of leaving protected openings at regular intervals to relieve water-vapor pressure in the insulation.
ElasticityThe property of matter in which it regains original size and shape after the removal of stress.
ElastomerThis refers to a macromolecular material which rapidly returns to its approximate initial dimensions following a release of stress.
EmulsionA dispersion of fine particles of a liquid within a liquid.
End lapThe overlapping ends of two panels.
EnvelopeA continuous edge seal formed by extending one ply of felt beyond the edge of the assembly. Once other plies are in place, the extended ply is turned back and adhered.
EPDMEthylene propylene diene monomer – a type of roofing membrane.
Expansion jointA structural separation between two building elements to allow free movement in the form of expansion and contraction without damage to the roofing system.
FabricationA manufacturing process performed in a plant which converts raw materials into finished components.
FasciaThis is a decorative trim projecting from the face of the wall. It serves as a weather closure.
FeltA flexible sheet manufactured by the interlocking of fibers through mechanical means, moisture, and heat. Roofing felts are made from vegetable fibers, glass fibers, or polyester fibers and are not spun, woven, or knitted.
Fiberglass insulationThis ia a blanket insulation comprised of glass fibers to insulate roofs.
Flashing cementThis is a mixture of cutback bitumen, mineral stabilizers, and fibers.
Flat asphaltA roofing asphalt that conforms to Specification D312, Type II.
GravelCoarse, granular aggregate, with pieces larger than grains of sand. This is a result of the natural erosion of rock.
Gravel stopThis is a device designed to prevent loose aggregate from washing off the roof.
GutterA channel installed at the eave of a roof to carry water to a drain or the ground.
“Hot stuff” or “Hot”A roofer’s term for hot bitumen
InclineThe slope of a roof expressed in percent or in the number of vertical units of rise over run.
IsothermThis refers to the line on a display screen that indicates equal apparent temperatures. On an imaging scanner, this is highlighted on the display as white.
JoistA small beam arranged parallel from wall to wall to support a floor, ceiling, or roof.
Kick-out (elbow)A lower portion of a downspout which directs water away from a wall.
LapThe area where a felt covers an underlying felt in a BUR membrane. This term is also used in single-ply membranes. An end lap occurs at the end of a roll, while an edge lap indicates a transverse cover.
Lapped jointThis term applies to an joint made by placing one surface to be joined partly over another surface to be joined and bonding the overlapping area.
LEEDLeadership in Energy and Environmental Design
Life-cycle costing This analytical technique allows for a systematic comparison of economic alternatives over the useful lifetime of the asset or product.
Maintenance and Repair CostThe total cost of labor, materials, and other related costs which are incurred for preventative maintenance or repair to an asset.
MasonryAnything built from bricks, concrete blocks, concrete, or a similar stone material.
MembraneThis term is used to describe any flexible or semi flexible roof covering with the primary function to exclude water.
Metal flashingThis is frequently used as a through-wall cap flashing or counterflashing.
MoppingThis is the process of applying hot bitumen to a built-up or modified bitumen roofing system.
NeopreneThis is a synthetic rubber used in either liquid or sheet applied elastomeric roofing membranes or flashing.
ParapetThe portion of a wall above the roof line.
PerliteThis is an aggregate that is used in lightweight insulating concrete and preformed perlite insulating boards. It is formed by heating and expanding siliceous volcanic glass.
Phased applicationThe process of installing a roofing system during two or more separate time intervals.
PlyA layer in a roofing membrane is called a ply.
PondA roof area which retains water instead of draining after a rain.
PondingWater which remains in a low or irregular roof area for more than 48 hours after a rain.
Preventative maintenanceRegular, scheduled inspection of a roofing system to repair normal breakdown.
ReroofingThis is the replacement of a defective roofing system with a new one.
RetrofitThe modification of an existing building to include a new system.
RidgeThis refers to the highest point of the roof of a building – generally a horizontal line running the entire length.
Ridge capThis refers to the transition of the roofing material along the ridge of a roof.
RIEIRoofing Industry Educational Institute
Roll roofingThis term refers to coated felts which are either smooth or mineral-surfaced. Roofing materials which come in a roll.
Roof coveringThis is the exposed area of the roof.
Roof curbThis refers to an accessory used to mount and level units such as HVAC on a sloped portion of a roof.
Roof jackThis accessory covers pipes (vents or flues) which penetrate the roof panel.
Roof overhangA roof extension beyond the endwall of a building is called a roof overhang.
Roof system This refers to the weatherproofing, insulating, and protective system designed to cover a building.
Sacrificial protectionAn example of this is galvanic protection. This process reduces the extent of corrosion of a metal in an electrolyte by coupling it to another metal which is electrochemically more active in the environment.
SBASystem Builders Association
SBCStandard Building Code
SBCCISouthern Building Code Congress International
ScrimUsed in the reinforcement of polymeric sheeting, this is an open-mesh fabric woven from continuous-filament yarn.
ScupperThis is a channel through a parapet wall designed for drainage of the roof, usually as a safety overflow to limit ponded water caused by a clogged drain.
SealantThis ia a material used to close cracks or joints in a roofing system for leak protection. For example: Lap sealant is applied to exposed lap edges.
Sealing washerThis is a rubber washer with a metal back which is assembled on a screw to prevent water migration through the screw hole.
Seam strengthThis refers to the strength of a seam of material. Measured in shear or peel mode, this is reported in absolute units like pounds per inch of width, or as a percent of the sheeting strength.
Service lifeThe anticipated useful life of a building, component, or subsystem. For example: roofing system.
Shark finThis term refers to the curled felt projecting upward through the flood coat and aggregate of a BUR membrane.
SIThe international system of metric units.
Side lapThe continuous overlap of closures along a side panel.
Single slopeA sloping roof with one surface.
SkylightThis is a rooftop accessory designed to admit light – usually mounted on a curb.
SlippageRelative lateral movement of adjacent felts or sheets in a roofing membrane. Most often seen on sloping roofs, this sometimes exposes the lower plies or base sheet to the elements.
SlopeExpressed as a percentage of rise per foot of horizontal distance, this is the tangenet of the angle between the roof surface and the horizontal plane.
Smooth-surface roofThis is a roof membrane without aggregate.
SoffitThis refers to the covering of the underside of a roof’s exterior overhang, sidewall, or gable.
Solar reflectance index (SRI)The SRI is the measure of a roof’s ability to reflect solar heat. This is shown by a small temperature rise, defined so that a standard black is 0 and a standard white is 100. The calculation of SRI follows the ASTM method E1980.
SquareA roof area of 100 square feet.
Stack ventThis is a vertical outlet designed to relieve pressure exerted by water vapor between a membrane and the deck (or a vapor retarder).
Stainless steelWith an excellent reistance to corrosion, this steel alloy contains a high percentage of chromium. It may also contain nickel or copper.
Standing water testAn evaluation in which test panels are submerged in aqueous solutions and then air dried.
StrainDeformation of a material under stress.
StressA measure of the load on a structural member in terms of force per unit area or the force acting across a unit area in a solid material in resisting the separation, compacting, or sliding that may be induced by external forces.This term also applies to the ratio of applied load.
SubstrateThis is the surface that a roof component is placed, like a structural deck or insulation.
Tar boilsAlso known as blueberries, blackberries, and strawberries, these are bubbles of moisture vapor encased in a thin film of bitumen.
Tear OffThis term refers to the removal of a failed or expired roof system down to the deck surface.
Thermal conductance (C)This is the rate of heat flow in Btus per hour through a square foot of material – or combination of materials – with surfaces having a temperature differential of 1 degree F..
Thermal conductivity (k)This is the rate of heat flow in Btus per hour through a square foot of material exactly one inch thick with a temperature differential of 1 degree F.
Thermal insulationAny material designed to reduce conductive heat flow.
Thermal resistance (R)This is resistance to heat flow and the reciprocal of conductance (C).
Thermal shockThis is stress caused by sudden temperature drops in a roof membrane. For example, thermal shock may occur when a rainstorm follows a warm, sunny day.
ThermogramThis refers to the visible light record of a infrared camera system display.
ThermographyThis technique produces heat pictures from the radiant energy emitted from a stationary or moving object without influencing the temperature in any way. This results in an electronic display of a visible image of an infrared spectrum.
Time value of moneyThe theory that money available at the present time is worth more or less than the same amount at a future date due to inflation or deflation. This is also called the present discounted value. This term is also used to refer to the changes in purchasing power and the real earning potential of an investment over time.
TPOTPO is a weldable thermoplastic sheet used as a single-ply membrane.
TrimOften referred to as flashing, this is a lightgage metal used to finish a building, particularly around openings and at intersections of surfaces.
UBCUniform Building Code
Vapor barrier
Vapor retarder
A material which resists the flow of water vapor
VentThis is an opening designed to allow the emittance of water vapor or other gases from the inside of a building.
VentilatorA ventilator is an accessory typically used as a pass-through for air.
VermiculiteThis aggregate is used in lightweight insulating concreate and is formed through the heating and expansion of a micaceous material.
ViscosityMeasured in centistokes (cSt) for bitumens, this is the index of a fluid’s internal resistance to flow. Water has a viscosity of 1 cSt. Light cooking oil has a viscosity of 100 cSt.
VulcanizationThis irreversible process changes the chemical structure of a rubber compound to amke it less plastic and more resistant to swelling by orgainc liquits. This improves, conferrs or extends the elastic properties over a greater temperature range.
WarpThis is the lengthwise yarns in a woven fabric.
WaterproofingThe treatment of a surface as a preventative for the passage of water under hydrostatic pressure.
Wind upliftThe upward-acting pressure which results from air motion across a roof.