Roofing Glossary

Algae discoloration: A type of roof discoloration caused by algae. Commonly called fungus growth.
Air Barrier: The assembly of materials used in building construction to reduce or slow the passage of air into and out of the building.
Angled Fasteners: Roofing nails and staples driven into decks at an angle – not perpendicular to the roof deck surface.
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.
APA: The Engineered Wood Association: The APA: The Engineered Wood Association is a trade organization that develops product standards, installation standards, and does certification testing of engineered wood products such as plywood and OSB (oriented strand board).
Apron Flashing: Metal flashing used at chimney or dormer fronts.
ARMA: Asphalt Roofing Manufacturers Association is an organization of asphalt roofing manufacturers.
ASTM: American Society for Testing and Materials. A voluntary organization concerned with development of consensus standards, testing procedures and specifications.
Asphalt: Asphalt is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch.
Asphalt Plastic Cement: A solvent-based asphalt sealant used for hand sealing shingles and sealing other locations on asphalt roofs. Meets ASTM D4586 Type I or II.
Asphalt Primer: Asphalt-based primer used to prepare the surface of concrete, metal, or other materials to enhance the adhesion of asphalt adhesives or asphalt sealant. Meets ASTM D41.
Asphalt roofing cement: An asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic; should conform to ASTM D4586.
Back surfacing: A material (normally a fine-mineral material) applied to the back of shingles or roll products to keep them from sticking together in the package during shipping, storage, and delivery.
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.
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: First layer or base ply in low-slope multi-ply roofing systems.
Blisters: Bubbles that may appear on the surface of asphalt roofing after installation.
Blow-Offs: When shingles are subjected to high winds and are forced off a roof deck by the wind.
Brands: Airborne burning embers released from a fire.
Bridging: A method of reroofing with metric-sized shingles.
Buckling: A visible wrinkle or ripple in shingles or underlayments.
Built-up roof: A flat or low-slope roof consisting of multiple layers of asphalt and ply sheets.
Bundle: A package of shingles. There are 3, 4 or 5 bundles per square.
Butt edge: The lower edge of the shingle tabs.
Cap Sheet: Top or final layer on low-slope roof systems.
Cant Strips: A triangular strip of material typically used on low-slope roofs for deflecting water away from flashing areas.
: To fill a joint with mastic or asphalt cement to help prevent leaks.
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”: 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-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating from sources outside the building.
Class “C”: 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.
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.
Cool Roof: A roof system that uses products with a top surface of highly-reflective and emissive material. Cool roof surfaces can remain at markedly lower temperatures when exposed to solar heat in service than surfaces of roofs constructed with traditional non-reflective roofing products. Timberline® Cool Series® is one example.
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.
Cutout: The open portions of a strip shingle between the tabs.
Damper: An adjustable plate for controlling draft.
Deck: The surface installed over the supporting framing members to which the roofing is applied.
Dormer: A framed window unit projecting through the sloping plane of a roof.
Double coverage: Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.
Downspout: A pipe for draining water from roof gutters. Also called a leader.
Drip edge: A noncorrosive, nonstaining material used along the eaves and rakes to allow water runoff to drip clear of underlying construction.
Dutch lap method: Application of very large individual shingles with the long dimension parallel to the eaves. Shingles are applied to overlap adjacent shingles in each course as well as the course below.
Dragon Teeth: The exposed section of double thickness on Timberline® Shingles – also called saw-teeth. Shaped to imitate a wood shake look on the roof.
Eaves: The horizontal, lowest edge of a sloped roof that extends beyond the exterior wall.
Eaves flashing: Additional layer of roofing material applied at the eaves to help prevent damage from water backup.
Edging strips: Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for reroofing with asphalt shingles.
Ell: An extension of a building at right angles to its length.
End Laps: When installing rolled products in roofing, the area where a roll ends on a roof and is overlapped by the next section of rolled material.
Exposed nail method: Application of roll roofing in which all nails are driven into the cemented, overlapping course of roofing. Nails are exposed to the weather.
Exposure I grade plywood: Type of plywood approved by the American Plywood Association for exterior use.
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 horsefeathers.
Felt: Fibrous material saturated with asphalt and used as an underlayment or sheathing paper.
Fiberglass mat: An asphalt roofing base material manufactured from glass fibers.
FHA: Federal Housing Authority.
Flange: The flat metal extending out on the roof from around flashing pieces, usually at chimneys and plumbing vents.
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. Galvanized metal flashing should be minimum 26-gauge.
Flashing cement: Sealant designed for use around flashing areas as a component in the flashing system, typically thicker than asphalt plastic cement.
FM: Factory Mutual Research Corp.
Free-tab shingles: Shingles that do not contain factory-applied strips or spots of self-sealing adhesive.
Gable: The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.
Gable roof: A type of roof containing a sloping plane on each side of a single ridge with a gable at each end.
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.
Gutter: The trough that channels water from the eaves to the downspouts.
Hand-Sealing: The method to assure sealing of shingles on very steep slopes, in high-wind areas, and when installing in cold weather.
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.
Hip: The inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.
Hip Legs: The down-slope ridges on hip roofs.
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 & Ridge Cap Shingles: The final layer of the roof at the ridge or hip, used to ensure protection at the highest areas of the roof and to accentuate the natural beauty of the roof by adding dimension and depth.
High Nailing: When shingles are nailed or fastened above the manufacturer’s specified nail location.
Horsefeathers: See feathering strips.
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.
Laminated shingles: Strip shingles containing more than one layer of tabs to create extra thickness. Also called dimensional or architectural shingles.

Lap: To cover the surface of one shingle or roll with another.
Lap cement: An asphalt-based cement used to adhere overlapping plies of roll roofing.
Low slope application: Method of installing asphalt shingles on roof slopes between two and four inches per foot.
Louver: A slanted opening for ventilation.

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. Includes no gables.
Masonry primer: An asphalt-based primer used to prepare masonry surfaces for bonding with other asphalt products.
Mastic: See asphalt plastic roofing cement.
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: Rolled roofing membrane with polymer modified asphalt and either polyester or fiberglass reinforcement.
Mold: A surface growth of fungus on damp or decaying matter. The term has no taxonomic significance and is used only in a general sense of visible fungal growth on organic matter.
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.
Nail-Pop: When a nail is not fully driven or backs out of the roof deck, that can cause overlaying shingles to raise or can result in nail heads breaking through overlaying shingles.
Nesting: The practice of installing a second layer of shingles over existing shingles in reroof applications where the top edge of the new shingles is butted against the bottom edge of the existing shingles to help provide a smoother installation.
Net Free Vent Area (NFVA): Area unobstructed by screens, louvers or other materials.
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.
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 flashing is exposed.
Organic felt: An asphalt roofing base material manufactured from cellulose fibers.
OSB: Oriented Strand Board, a decking made from oriented wood chips and lamination glues.
Overhang: That portion of the roof structure that extends beyond the exterior walls of a building.
Organic Shingles: Shingles made using a base reinforcement of organic (paper) mats.
Pallets: Wooden platforms used for storing and shipping bundles of shingles.
Pitch: The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet.
Ply: The number of layers of roofing (e.g. one-ply, two-ply).
Pipe Boot: A pre-flashed flashing unit for flashing plumbing vent pipes or other round roof penetrations.
Plumbing Vents: A term used to describe plumbing pipes that project through the roof plane. Also called vent stacks.
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.
Racking: Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. Not a recommended procedure.
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.
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: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
Ridge shingles: Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.
Rise: The vertical distance from the eaves line to the ridge.
Roll roofing: Asphalt roofing products manufactured in roll form.
Roof Plane: An even roofing area defined by having separate edges. One side of a gable, hip, or mansard roof.
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 tape: An asphalt-saturated tape used with asphalt cement for flashing and patching asphalt roofing.
Run: The horizontal distance from the eaves to a point directly under the ridge. One half the span.
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.
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.
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.
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.
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.
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.
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.
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.
UL: Underwriters Laboratories, LLC.
UL label: Label displayed on packaging to indicate the listing for fire and/or wind resistance of asphalt roofing.
Undereave: Underside area of the overhang at the eave of the roof.
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.
Valley: The internal angle formed by the intersection of two sloping roof planes to provide water runoff.
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: Any outlet for air that protrudes through the roof deck, such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck.
Vent sleeve: See collar.
Ventilators: Devices that eject stale air and circulate fresh air (e.g. ridge, roof, gable, undereave, foundation or rafter vents and vented soffit panels).
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.

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