Terms and Glossary of Roofing
A
Air Barrier: A structurally supported component of the building envelope which prevents the migration of air between the building interior and the outside environment.
Algae Discoloration: A type of roof discoloration caused by algae. Commonly called fungus growth.
ALLIGATORING: A pattern of cracking on exposed bitumen like the appearance of an alligator's hide, due to oxidation of the bitumen.
American method: Application of very large individual shingles with the long dimension parallel to the rake. Shingles are applied with a 3/4-inch space between adjacent shingles in a course.
AREA DIVIDER: A roofing element usually fabricated from dimension wood component incorporated into a roofing system to subdivide large roof areas or at changes in structural deck direction or deck types, to control membrane stresses (See also Subsurface Roof Divider).
Asphalt roofing cement: An asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic; should conform to ASTM D4586.
ASPHALT: A bituminous material derived from the distilling of crude oil.
Asphalt: A bituminous waterproofing agent applied to roofing materials during manufacturing.
ASTM: American Society for Testing and Materials. A voluntary organization concerned with development of consensus standards, testing procedures and specifications.
AUXILIARY LEVELLING SURFACE: A substrate material such as gypsum board, plywood or fiberboard used to provide a smooth surface to which a membrane may be adhered.
B
BACK NAILING: The practice of fastening membrane plies so that the fasteners are covered by subsequent plies and are not exposed to the weather.
Back surfacing: Fine mineral matter applied to the back side of shingles to keep them from sticking.
Balanced system: A ventilation system where 50% of the required ventilating area is provided by vents located in the upper portion of the roof with the balance provided by undereave or soffit vents.
BALLAST: Loose-laid roofing gravel or pavers whose mass is used to control movement from wind uplift or floatation of insulation or the primary membrane.
Base flashing: That portion of the flashing attached to or resting on the deck to direct the flow of water onto the roof covering.
BASE SHEET: A heavy sheet of saturated or coated felt or the bottom ply of a two-ply modified bitumen membrane.
BITUMEN: A generic term describing any mixture of heavy hydrocarbons in viscous form used in the roofing industry as an adhesive and waterproofing agent. Bitumens are subdivided into asphalt and coal tar pitch.
Blisters: Bubbles that may appear on the surface of asphalt roofing after installation.
BONDING ADHESIVE: The adhesive required to adhere a single ply membrane to its substrate.
Brands: Airborne burning embers released from a fire.
Bridging: A method of reroofing with metricized shingles.
Built-up roof: A flat or low-slope roof consisting of multiple layers of asphalt and ply sheets.
BUILT-UP ROOFING (BUR): A continuous semi-flexible membrane comprised of plies of organic or inorganic asphalt saturated felts adhered into full inter-ply mopping of bitumen.
Bundle: A package of shingles. There are 3, 4 or 5 bundles per square depending on type.
Butt edge: The lower edge of the shingle tabs.
C
California Valley A California cut valley is a roofing technique commonly used to create a weathertight intersection between two sloping roof planes. Unlike traditional valley flashing methods, which may involve the use of metal, the California cut valley relies on precise cuts and overlapping shingles to direct water away from the valley.
CANT STRIP: A triangular shaped strip of wood or fiberboard that forms a beveled transition for membranes between the horizontal to vertical planes.
CAP SHEET: The upper ply of two ply modified bitumen membrane which is fully adhered to the base sheet.
Caulk: To fill a joint with mastic or asphalt cement to help prevent leaks.
CAULKING: An elastomeric material used to seal and make watertight overlapping components.
Cement: See asphalt roofing cement.
Chalk line: A line made on the roof by snapping a taut string or cord dusted with chalk. Used for alignment purposes.
Class "A" Fire Rating: The highest fire-resistance rating for roofing as per ASTM E108. Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.
Class "B" Fire Rating: Fire-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating from sources outside the building.
Class "C" Fire Rating: Fire-resistance rating that indicates roofing materials are able to withstand light exposure to fire originating from sources outside the building.
Closed cut valley: A method of valley treatment in which shingles from one side of the valley extend across the valley, while shingles from the other side are trimmed two inches from the valley centerline. The valley flashing is not exposed.
COAL TAR PITCH: A bituminous material derived from the cooking of coal.
Coating: A layer of viscous asphalt applied to the base material into which granules or other surfacing is embedded.
Collar: Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. Also called a vent sleeve.
Concealed nail method: Application of roll roofing in which all nails are driven into the underlying course of roofing and covered by a cemented, overlapping course. Nails are not exposed to the weather.
Condensation: The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.
Counter flashing: That portion of the flashing attached to a vertical surface to help prevent water from migrating behind the base flashing.
Course: A row of shingles or roll roofing running the length of the roof.
Coverage: Amount of weather protection provided by the roofing material. Depends on number of layers of material between the exposed surface of the roofing and the deck (single coverage, double coverage, etc.).
Cricket: A peaked saddle construction at the back of a chimney to help prevent accumulation of snow and ice and to deflect water around the chimney.
CRICKET: An elevated element of a roofing system designed to direct water to drain receptacles or divert around an obstacle such as a chimney.
CURB: A wooden or metal structure surrounding roof openings or supporting mechanical equipment which permits the waterproofing membrane to terminate above the roof surface.
Cutout: The open portions of a strip shingle between the tabs.
D
Damper: An adjustable plate for controlling draft.
DECK: The structural element to which a roofing system is applied. Also see Structural Roof Deck.
Deck: The surface installed over the supporting framing members to which the roofing is applied.
DEW POINT: The temperature at which a specific atmosphere is saturated with water vapor or at which air has 100% relative humidity.
Dormer: A framed window unit projecting through the sloping plane of a roof.
Downspout: A pipe for draining water from roof gutters. Also called a leader.
Drip edge: A noncorrosive, non-staining material used along the eaves and rakes to allow water runoff to drip clear of underlying construction.
E
Eaves: The horizontal, lowest edge of a sloped roof that extends beyond the exterior wall.
EDGE LAP: The overlap of the edge of a ply over the previous ply. Also called a side lap.
Edging strips: Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for reroofing with asphalt shingles.
ELECTRONIC LEAK DETECTION: Non-destructive testing for the purpose of locating breaches in the waterproofing layer of a roof assembly by means of a leak sensor using low voltage electrical power.
EPDM: Ethylene Propylene Diene Monomer, a single ply membrane manufactured from synthetic rubber.
EXPANSION JOINT: A structural separation used to permit differential movement of a structure caused by expansion and contraction of its elements due to temperature change. A designed separation in the primary membrane to permit such movement, extending above the roof surface.
Exposure I grade plywood: Type of plywood approved by the American Plywood Association for exterior use.
F
Feathering strips: Tapered wood filler strips placed along the butts of old wood shingles to create a level surface when reroofing over existing wood shingle roofs. Also called horse feathers.
Felt Paper: Fibrous material saturated with asphalt and used as an underlayment or sheathing paper.
Fiberglass mat: An asphalt roofing base material manufactured from glass fibers.
Fire Rated Plywood: Fire-rated plywood is a type of engineered wood product specifically treated to resist flame and heat, providing enhanced safety in construction and interior applications. It is commonly used in areas where building codes require materials that meet certain fire-resistance ratings. Common in Townhouse’s built after 1986.
FISHMOUTH: Wavy or scalloped openings occurring at the lapped edges of roofing felts and membranes.
FLASH OFF: The time required for the volatiles in a petroleum-based adhesive/primer to escape into the atmosphere prior to bonding.
Flashing cement: See asphalt roofing cement.
Flashing: Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys.
Free-tab shingles: Shingles that do not contain factory-applied strips or spots of self-sealing adhesive.
G
Gable roof: A type of roof containing a sloping plane on each side of a single ridge with a gable at each end.
Gable: The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.
Gambrel roof: A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. Features a gable at each end.
Granules: Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.
GRAVEL STOP: A flanged metal flashing with an upturned exterior edge, with its horizontal flange sealed to the membrane, installed to provide a finished edge for the termination of roofing components.
Gutter: The trough that channels water from the eaves to the downspouts and away from the foundation of your home.
H
Head lap: Shortest distance from the butt edge of an overlapping shingle to the upper edge of a shingle in the second course below. The triple coverage portion of the top lap of strip shingles.
HEX shingles: Shingles that have the appearance of a hexagon after installation.
HIGH DENSITY COVERBOARD: A High-Density (HD) Coverboard is defined as a material with a minimum compressive strength 80 PSI used over roof insulation to provide protection to the insulation during installation and service.
Hip roof: A type of roof containing sloping planes of the same pitch on each of four sides. Contains no gables.
Hip shingles: Shingles used to cover the inclined external angle formed by the intersection of two sloping roof planes.
Hip: The inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.
Horsefeathers: See feathering strips.
I
Ice and Water Shield: A critical roofing underlayment designed to protect your home from water damage caused by ice dams and roof leaks. This heavy-duty membrane is typically installed in areas most susceptible to moisture, such as eaves, valleys, and around penetrations like chimneys and vents.
Ice dam: Condition formed at the lower roof edge by the thawing and refreezing of melted snow on the overhang. Can force water up and under shingles, causing leaks.
Interlocking shingles: Individual shingles that mechanically fasten to each other to provide wind resistance.
Impact Rated Shingle: In 1996 the Institute of Business and Home Safety (IBHS) and the Underwriter’s Laboratory (UL) developed the UL 2218 classification, a national standard for roof impact resistance by rating materials from Class 1 through 4, based on their resistance to the steel ball simulation test. A Class 4 rating is the toughest.
Impacted Class 1: Sample did not crack when hit twice in the same spot by a steel ball 1.25 inches in diameter.
Impacted Class 2: Sample did not crack when hit twice in the same spot by a steel ball 1.50 inches in diameter.
Impacted Class 3: Sample did not crack when hit twice in the same spot by a steel ball 1.75 inches in diameter.
Impacted Class 4: Sample did not crack when hit twice in the same spot by a steel ball 2.00 inches in diameter.
L
Laminated shingles: Strip shingles containing more than one layer of tabs to create extra thickness. Also called dimensional or architectural shingles.
Lap cement: An asphalt-based cement used to adhere overlapping plies of roll roofing.
Lap: To cover the surface of one shingle or roll with another.
LOOSE LAID BALLASTED SYSTEMS: Roofing systems where assembly components are not uniformly adhered to their substrate and where ballast is employed to stabilize movement of the primary membrane and provide wind uplift resistance.
Louver: A slanted opening for ventilation.
Low slope application: Method of installing asphalt shingles on roof slopes between three and four inches per foot.
M
Mansard roof: A type of roof containing two sloping planes of different pitch on each of four sides. The lower plane has a much steeper pitch than the upper, often approaching vertical.
Masonry primer: An asphalt-based primer used to prepare masonry surfaces for bonding with other asphalt products.
Mastic: See asphalt plastic roofing cement.
MECHANICALLY FASTENED SYSTEMS: Roofing systems in which roofing components or primary membrane are uniformly attached to the structural deck with mechanical fasteners in a prescribed pattern.
MEMBRANE FLASHING: The vertical extension of the waterproofing membrane installed at horizontal to vertical junctions at roof penetrations and membrane terminations.
MEMBRANE: A continuous flexible or semi-flexible element that functions as a waterproof covering. Membrane can be single ply or multi-ply systems.
Mineral stabilizers: Finely ground limestone, slate, traprock or other inert materials added to asphalt coatings for durability and increased resistance to fire and weathering.
Mineral-surfaced roofing: Asphalt shingles and roll roofing that are covered with granules.
MODIFIED BITUMEN MEMBRANES: Composite roofing membrane comprised of a reinforcing sheet coated on one or both sides with a polymer modified asphalt which may be surfaced with poly film, sand or mineral granules.
MUD CURLING: The result of sediment buildup in roof areas subject to prolonged periods with ponding water.
N
NAILING STRIPS (NAILRS): Wood blocking or strips secured to roof decks, walls or curbs to permit anchoring of roofing membranes, insulation or membrane flashing.
Natural ventilation: A ventilation system utilizing ventilators installed in openings in the attic and properly positioned to take advantage of natural air flow to draw hot summer or moist winter air out and replace it with fresh outside air.
Nesting: A method of reroofing with new asphalt shingles over old shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle tab. It is never recommended to install new over old shingles.
Net Free Vent Area (NFVA): Area unobstructed by screens, louvers or other materials when measuring attic ventilation.
No-cutout shingles: Shingles consisting of a single, solid tab with no cutouts.
Non-veneer panel: Any wood-based panel that does not contain veneer and carries an APA span rating, such as wafer board or oriented strand board.
Normal-slope application: Method of installing asphalt shingles on roof slopes between 4 inches and 21 inches per foot.
O
OIL CANNING: The buckling and minor deformation of light gauge sheet metal that results in a wavy or uneven finished appearance caused by stresses at their attachment points.
Open valley: Method of valley construction in which shingles on both sides of the valley are trimmed along a chalk line snapped on each side of the valley. Shingles do not extend across the valley. Valley metal flashing is exposed.
Organic felt: An asphalt roofing base material manufactured from cellulose fibers.
Overhang: That portion of the roof structure that extends beyond the exterior walls of a building.
P
Pallets: Wooden platforms used for storing and shipping bundles of shingles.
PARAPET: A structural extension or low wall installed at the roof edge extending above the roof surface.
PERIMETER: The outside edge of a self-contained roof area.
Pitch: The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet.
PLASTIC CEMENT: A mixture of bitumen, fibers, fillers and a suitable solvent combined to form bituminous cement used as a sealing material.
Ply: The number of layers of roofing (e.g. one-ply, two-ply).
PONDING: The accumulation or pooling of water at a low-lying area of a roof.
POSITIVE DRAINAGE: The criterion for judging proper slope for positive drainage is that there be reduced ponding water on the roof 72 hours after rain, during conditions conducive to drying. A thin liquid bituminous or synthetic resin compound applied to a substrate to improve adhesion of membranes or adhesives.
PVC: A thermoplastic membrane composed of a reinforced single ply sheet coated with PVC produced by the polymerization of vinyl chloride. Membrane laps are bonded by hot air welding.
Q
Quick-setting cement: An asphalt-based cement used to adhere tabs of strip shingles to the course below. Also used to adhere roll roofing laps applied by the concealed nail method.
R
Racking: Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. Not a recommended procedure for architectural shingles but can be a requirement for some luxury shingles
Rafter: The supporting framing member immediately beneath the deck, sloping from the ridge to the wall plate.
Rake: The inclined edge of a sloped roof over a wall from the eave to the ridge.
Random-tab shingles: Shingles on which tabs vary in size and exposure.
REGLET: A cut joint into a wall surface to act as a receiver for the attachment of the sheet metal counter flashing.
Release tape: A plastic or paper strip that is applied to the back of self-sealing shingles. This strip prevents the shingles from sticking together in the bundles and need not be removed for application.
Ridge or Cap shingles: Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.
Ridge Vent: A bendable vent that is placed at the ridge of the roof. The correct amount of decking is removed based on your required NFVA. Installed on roof pitches from a three to a twelve inches per foot pitch.
Ridge: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
RIDGING: An upward elongated tenting or displacement of a membrane frequently occurring over insulation or deck joints.
Rise: The vertical distance from the eaves line to the ridge.
Roll roofing: Asphalt roofing products manufactured in roll form.
ROOF COVERING: Water shedding or waterproofing material that covers a substrate to protect the roof assembly from moisture penetration.
Roofing cement: A compound used to seal flashings, seal down shingles and for other small waterproofing jobs. Where cement is required for sealing down shingles, use a dab about the size of a quarter unless otherwise specified.
ROOFING GRAVEL: Uniformly graded and washed round rock or crushed stone used as a protective surface layer over built-up roofing systems.
Roofing tape: An asphalt-saturated tape used with asphalt cements for flashing and patching asphalt roofing.
Run: The horizontal distance from the eaves to a point directly under the ridge. One half the span.
S
Saturant: Asphalt used to impregnate an organic felt base material.
Saturated felt: An asphalt-impregnated felt used as an underlayment between the deck and the roofing material.
Scupper: An opening through a parapet or wall which permits the drainage of water from the roof surface.
Seam Lap Sealant: A roofing product developed to continuously seal exposed single ply membrane splice seam edges (laps) from water infiltration.
Seam Tape: A manufactured pressure sensitive adhesive tape used to seal/bond the laps of adjacent single ply thermoset membrane sheets.
Self-sealing cement: A thermal-sealing tab cement built into the shingle to firmly cement the shingles together automatically after they have been applied properly and exposed to warm sun temperatures. In warm seasons, the seal will be complete in a matter of days. In colder seasons, sealing time depends on the temperature and amount of direct sunlight hitting the shingles. Hand sealing with cement should be done to ensure sealing in winter.
Self-sealing shingles: Shingles containing factory-applied strips or spots of self-sealing adhesive.
Self-sealing strip or spot: Factory-applied adhesive that bonds shingle courses together when exposed to the heat of the sun after application.
Selvage: That portion of roll roofing overlapped by the succeeding course to obtain double coverage.
Separator Sheet or Slip Sheet: A material used to reduce transmission of stress between roofing components, or to prevent layers from adhering together.
Shading: Slight differences in shingle color that may occur as a result of normal manufacturing operations.
Sheathing: Exterior-grade boards used as a roof deck material.
Shed roof: A roof containing only one sloping plane. Has no hips, ridges, valleys or gables.
Sheet Metal Flashing: Galvanized or prefinished metal sheets which are formed and installed to protect bituminous membrane flashing from physical and solar damage.
Single coverage: Asphalt roofing that provides one layer of roofing material over the deck.
Slope: The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.
Smooth-surfaced roofing: Roll roofing that is covered with ground talc or mica instead of granules (coated).
Soffit: The finished underside of the eaves.
Soffit: Underside area of the overhang at the eave of the roof.
Soil stack: A vent pipe that penetrates the roof.
Span: The horizontal distance from eaves to eaves.
Specialty eaves flashing membrane: A self-adhering, waterproofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain.
Square: A unit of roof measure covering 100 square feet.
Square-tab shingles: Shingles on which tabs are all the same size and exposure.
Starter strip: Asphalt roofing applied at the eaves that provides protection by filling in the spaces under the cutouts and joints of the first course of shingles.
Static Vent: These vents have no moving parts and can have louvered sides to protect from weather. They allow hot moist air to escape from the attic.
Steep-slope application (Mansard): Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.
Step flashing: Flashing application method used where a vertical surface meets a sloping roof plane.
Strip shingles: A single-layer shingle commonly known as a three-tab shingle because it has three tabs.
Structural Roof Deck: The structural component of the roof of a building capable of supporting the designed dead and live loads, including the weight of the roof system.
Substrate: A supporting surface upon which the roof covering or membrane is adhered or applied.
Synthetic roof Underlayment: Roofing accessory that's made from polymers like polypropylene or polyethylene, designed to protect the roof deck from moisture and damage. A new option to felt underlayment.
T
Tab: The exposed portion of strip shingles defined by cutouts.
Talc: See back surfacing.
Telegraphing: A shingle distortion that may arise when a new roof is applied over an uneven surface.
Thermal Barrier: A non-combustible material such as gypsum boards applied to a structural substrate to slow the temperature rise of roofing system components.
Three-dimensional shingles: See laminated shingles.
Three-tab shingle: A single-layer shingle having three tabs.
Top lap: That portion of the roofing covered by the succeeding course after installation.
TPO: Thermoplastic Olefin, is a popular roofing membrane choice known for its energy efficiency, durability, and ease of installation. Composed of a blend of polypropylene and ethylene-propylene rubber, TPO roofs are highly reflective, which helps reduce heat absorption and can lower cooling costs for buildings.
U
UL label: Label displayed on packaging to indicate the listing for fire and/or wind resistance of asphalt roofing.
Underlayment: A layer of asphalt-saturated felt (sometimes referred to as tar paper) which is laid down on a bare deck before shingles are installed to provide additional protection for the deck.
V
Valley: The internal angle formed by the intersection of two sloping roof planes to provide water runoff.
Vapor Barrier/Retarder: A membrane used to retard the diffusion of moisture or water vapor into the components of a roofing system.
Vapor retarder: Any material used to prevent the passage of water vapor. Material which, when installed on the high-vapor-pressure (warm in winter) side of a material, retards the passage of moisture vapor to the lower-pressure (cold in winter) side. Note exception: Florida and Gulf Coast. Check local building codes to determine on which side the vapor retarder should be placed.
Vent sleeve: See collar.
Vent: Devices that eject stale air and circulate fresh air (e.g. ridge, roof, gable, soffit, foundation or rafter vents and vented soffit panels).
W
Walk Pads: Made from the same roofing membrane material that provide protection from foot and equipment traffic damaging the roof membrane.
Woven Valley: Method of valley construction in which shingles from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied. The valley flashing is not exposed.