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Roofing Terms

Roofing Termonolgy

If you are looking for a particular roofing word or phrase, please see our glossary below.

| A | B | C | D | E | F | G | H | I | L | M | N | P | R | S | T | U | V | W |

A
Algae Discoloration: A type of roof discoloration caused by algae. Commonly called fungus growth.

Alligatoring: Surface cracking due to oxidation and shrinkage stresses, which shows as mounding of an asphalt surface, resembling the hide of an alligator.

ARP Material: Asphalt Resistant Polymer / Asphalt Resistant Product.

Asphalt: A dark brown to black substance found in natural beds and is also obtained as a residue in petroleum or coal tar refining that consists chiefly of hydrocarbons. Asphalt is typically further refined to make a bituminous waterproofing agent used in most roofing manufacturing processes.

Asphalt Shingle: A shingle manufactured by coating a reinforcing material (felt or fibrous glass mat) with asphalt and having mineral granules on the side exposed to the weather.

Asphalt Plastic Roofing Cement: Asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic; should conform to ASTM D-4586.

ASTM: American Society for Testing and Materials. A voluntary organization concerned with development of consensus standards, testing procedures and specifications.

Attic: The open space between the underside of the roof sheathing and the upper side of the ceiling directly below the roof.

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B
Ballast: Aggregate such as river rock or concrete pavers used as an anchoring material to hold roofing material in place.

Base Sheet: A heavy sheet of felt sometimes used as the first ply in built-up roofing.

Base Flashing: (A) That portion of the flashing that is attached to or rests on the roof deck to direct the flow of water on the roof, or to seal against the roof deck. (B) A material applied to the base of a wall extending above a roof, as a protection for the junction of the wall, and the roof.

Bitumen: Bitumens are mixtures of hydrocarbons of natural or pyrogeneous origin; or combinations of both, frequently accompanied by their non-metallic derivatives, which may be gaseous, liquid, or solid, and which are completely soluble in carbon disulfide. In the roofing industry the word covers both asphalt and coal tar pitch.

Blind Nailing: Shingles nailed in such a location that when the next shingle is applied, the nails of the first shingle do not show.

Blisters: Blisters are caused by the expansion of trapped air and water vapor or other gases. Air and moisture trapped within the construction tend to expand during a rise in air temperature of from the heat of the sun. This expansion causes the plies of the roofing to separate and bulge the roof surface in a balloon effect.

Block Method: Method of applying shingles in vertical rows from eave to peak instead of horizontal rows. This method makes shading more noticeable and can lead to improper fastening. Also called straight up method.

Bond: Adherence between elements of the roof system.

Boot: A covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc., from around a penetration. Also, a flexible material used to form a closure, sometimes installed at inside and outside corners.

Breather: A type of roof vent consisting of a hooded flanged pipe 2" to 8" in diameter, penetrating the roofing membrane to allow escape of moisture from insulation.

Buckling: Warping or wrinkling of the roof membrane.

Built-up Roofing: Layers of roofing felt bonded together on site. A protective surface coating of gravel or slag is sometimes embedded in a heavy top coating of hot bitumen.

Building Code: The minimum construction requirements established generally by national organizations of experts and adopted completely or in altered form by local governing authorities.

Bundle: A package of shingles. There can be 3, 4, 5 or even 6 bundles per square.

BUR: Built Up Roof. A semi-flexible multi-ply roof, consisting of plies or layers of saturated or coated felts, fabrics, or mats with bitumen between each layer. BUR roofs are normally surfaced with mineral aggregate, liquid coating or granule-surfaced cap sheet.

Butt Edge: The lower edge of the shingle tab.

Butyl Tape: A sealant tape sometimes used between metal roof panel seams and/or end laps. It is also used to seal other types of sheet metal joints, and in various other sealant applications.

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C
Cant: A beveled or triangular-shaped strip of wood, insulation or other material designed to serve as a gradual transitional plane between the horizontal surface of a roof deck and a parapet wall, or other vertical surface.

Cap Flashing: Portion of flashing built into a vertical surface to prevent the flow of water behind the base flashing. The cap flashing overlaps and caps off the top of the base flashing.

Caulk: To fill a joint with mastic or asphalt cement to prevent leaks.

Caulking: The physical process of sealing a joint or juncture, or sealing and making weather-tight the joints, seams or voids between adjacent surfaces by filling with a sealant.

Closed Valley: A valley where the flashing is covered by shingles.

Chalk Line: A line made on the roof or other flat surface by snapping a taut string or cord dusted with colored chalk.

Chemical Resistance: The ability of a material to withstand contact with specified chemicals without a significant change in properties.

Cleat: A continuous metal strip or angled piece, used to secure metal components at the perimeter metal details of a building.

Clip: A non-continuous metal component or angle piece used to secure two or more metal components together.

Coal Tar Pitch: A bituminous material produced by distilling crude tar residue derived from the cooking of coal. It is used as the waterproofing material for tar and gravel built-up roofing.

Collar: Pre-formed flange placed over a vent pipe to seal the penetration around the vent pipe opening.

Concealed Nailing: Application of roll roofing in such a manner as to conceal or cover all nail heads used to fasten the roofing to nail able decks.

Condensation: The change from water vapor to liquid water, resulting from a drop in temperature of an air vapor mixture.

Conductor: A pipe for conveying rainwater from a roof gutter to a drain or from a roof drain to a storm drain.

Coping: The cap or highest covering course of a wall, usually overhanging the wall and having a sloping top to carry off water.

Counter Flashing: Strips of metal, roofing, or fabric inserted and securely anchored to the reglet or attached to a vertical surface above the plane of the roof and turned down over the face flashing to protect the base flashing.

Course: Row of shingles that can run horizontally, diagonally or vertically.

Cold Tar Pitch: A coal tar-derived product used as the waterproofing agent in dead-level or low-sloped built-up roof membranes and membrane waterproofing systems, conforming to ASTM Specification D 450, Type I.

Combustible: Capable of burning.

Compatible Materials: Two or more substances that can be mixed, blended, or attached without separating, reacting, or affecting the materials adversely.

Concrete Nails: A nail specially designed for installation into concrete.

Concrete Screw: A special screw with high-low threads, specially designed for installation into concrete.

Contractor Responsibilities: The contractor is responsible for following all applicable plumbing, building, electrical and safety codes, using standard roofing practices and proper safety procedures, and following OSHA guidelines. The contractor must also assure that the installed system meets or exceeds all project specifications as well as all local and other safety rules, regulations, and codes.

Control Joint: A groove that is formed, sawed, or tooled into a concrete or masonry structure to regulate the location and amount of cracking and separation resulting from the dimensional change of different parts of the structure, thereby avoiding the development of high building stresses.

Conterflashing: Formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit or other surface to cover and protect the upper edge of a base flashing and its associated fasteners.

Coping Cap: The covering piece on the top of a parapet wall, usually made of metal, masonry, or stone.

Core Cuts: A series of sample cut outs that are taken through the existing roof, typically down to the roof deck. Core cuts determine the thickness, moisture, and makeup of the existing roofing assembly, as well as the type and length of fastener to be used.

Core Cutter: A tool used to make core cuts into the existing roof assembly.

Cracking: After long exposure, a fissure or fissure pattern appearing on the shingle of roofing due to weathering of the asphalt.

Cricket: A peaked saddle construction at the back of a chimney/protrusion, to prevent accumulation of snow and ice and to deflect water around the chimney/protrusion.

Curb: A wall of wood or masonry built above the level of the roof, surrounding a roof opening such as for installation of roof fans or other equipment.

Canted Curb: A curb or frame that is placed over an opening through the roof to support equipment such as air conditioners or other large units. If the curb or frame has a beveled 45-degree cant, it is called a "canted curb."

Cure: A process whereby a material forms permanent molecular linkages by exposure to chemicals, heat, pressure and/or weathering.

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D
Data Sheet: Provides a detailed description of the product and lists basic uses and installation guidelines.

Dead Load: The total weight of all installed materials and the constant weight of a roof used to compute the strength of all supporting framing members.

Deck/Roof Deck: The structural component of a roof that provides the substrate to which the roofing or waterproofing system is applied.

Dormer: A separate smaller roofed structure that projects from a sloping roof to provide more space below the roof and to accommodate a vertical window.

Downspout: A pipe conveying rainwater from a roof gutter to a drain.

Drip Edge: A modified L-shaped flashing used along the eaves and rakes. The drip edge directs runoff water into the gutters and away from the fascia.

Drain: An outlet on the roof used to collect and direct the flow of runoff water from a roof area.

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F
Face Nailing: Nailing with the nails placed in the exposed area of the metal, shingle or tile.

Fascia: A wood trim board used to hide the cut ends of the roof's rafters and sheathing. The gutter system is usually nailed to the fascia.

Felt: A very general term used to describe roll roofing materials, consisting of a mat of organic or inorganic fibers.

Felt (glass): A non-woven mat of flexible glass fiber, formed by spreading fibrous material over a screen and pressing it together to form a sheet.

Felt (15 & 30): Asphalt or coal tar saturated felt weighing approximately 15 or 30 pounds per 100 square feet.

Fire Wall: Any wall built for the purpose of restricting the spread of fire in a building. Such walls of solid masonry or concrete usually divide a building from the foundations to about a meter above the roof.

Fire-Resistant: Material that is resistant to catching on fire.

Fish Mouthing: The raising of a portion of the butt edge (lower edge) of a shingle. This curved short section tapers back into the shingle. Usually, only the front part of the shingle is affected. Often the result of moisture absorption followed by moisture evacuation in the shingle.

Fire Rating: UL Standards for External Fire Testing for Roof Coverings (UL 790). The requirements cover the performance of roof covering materials exposed to fire conditions originating from sources outside of buildings on which the coverings are installed. The UL 790 rates roof coverings as having a Class A, B, or C fire ratings.

Flashing: Metal strips used to form a watertight seal between the items butted up against the shingles. Flashing is used along walls, chimneys and dormers. Metal is usually 26 gauge galvanized sheet metal, but may be lead, copper, tin or aluminum.

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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 tan the upper, often approaching vertical – contains no gables.

Masonry Primer: An asphalt-based primer used to prepare masonry surfaces for bonding with other asphalt products.

Mastic: A tape like sealant used as water block.

Membrane: A saturated cotton or burlap fabric used for certain built-up roofing applications. Also a waterproofing system or roof covering.

Metal Anchors: Also known as “mollies.” Zinc plated and designed to be driven into a 1/4” hole and set with a hammer.

Mil: A unit of measure. One mil is equal to 0.001 inches, or 25.4 micrometers. Often used to indicate the thickness of a roofing membrane.

Monolithic: Formed from or composed of a single material; seamless.

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P
Pallet: Wooden platforms used for storing and shipping bundles or manufactured roofing product.

Panduit Band: A smooth, flat stainless steel band used in conjunction with sealant and caulk to terminate round stack flashings.

Panduit Tool: A tool used to tighten a Panduit band for a watertight termination on a round stack flashing.

Parapet Wall: The part of a perimeter wall that extends above the roof.

Parapet Wall Flashing: A custom made flashing for a wall on a roof.

Penetration: Any construction such as pipes, conduits, and HVAC supports that pass through the roof surface.

Pitch: Height from the joist to ridge divided by rafter length, which translates to rise in inches per horizontal foot or ratio of pitch. Ratio is a portion up to full pitch (24" in 12").

Pitch Pan or Pocket: Usually a rectangular flanged metal collar placed around metal supports that project above a roof deck. The pitch pan is placed on top of the roofing underlayment.

Pipe Flashing / Round Flashing: Custom made flashing, either open or closed and used for round roof penetrations such as vent and soil pipes.

Ply: A single layer or thickness of roofing material. Built-up roofs are described as three, four ply, etc., according to the number of layers used to build up the membrane.

Polyvinyl Chloride: PVC is a synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers and other modifiers. Rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.

Ponding: The collecting of water in shallow ponds on the top surface of roofing. Certain roofs are designed for the ponding water to a shallow depth over the whole surface of the roof deck, to aid in summer cooling. Many flat roof systems void their warranties if ponding water sits on the deck for more than 48hrs.

Positive Drainage: Slope that has been designed into a roof area to ensure drainage within 48 hours after the end of rainfall, when conditions are conducive to drying.

Primer: A cut back asphalt coating of thin consistency used on concrete or metal preparatory to prepare for bonding between the dissimilar materials.

Purlin: Boards laid from gable to gable on which the common rafters sit.

Pull Test: A test of a fastener using a Pull Tester on a deck/substrate to determine the fastener spacing for a roof installation. The less the pull, (measured in pounds of resistance) the greater the quantity of fasteners that will be needed along the deck sheet fastening tab. The greater the pull, the fewer fasteners that will be needed.

Pull Tester: Tool that measures the pounds of pull-out resistance.

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R
Rafters: The lumber supports that make up the roof structure. Usually 2" x 12" lumber. The roof sheathing is nailed to the rafters.

Reverse Lap: The first lap or laps on a deck sheet that “work” or “point” in the opposite direction of the rest of the laps on the sheet. This is done to help start a deck sheet in the right position and wrinkle free, and to locate the bulk of the material away from the edge or parapet wall.

Reverse Tab: The tab on the underside facing the opposite of the regular tabs and the first tab to come out of the roll. This tab is created from a “reverse lap,” and its primary purpose is for ease of installation. Reverse tabs can only be ordered at the beginning of the deck sheet and are used to start the deck sheet by giving the installer an edge to align the deck sheet to a snapped chalk line.

Reglet: A groove in the vertical wall adjacent to a roof surface, above the top of base flashing into which the metal counter flashing is placed and rigidly held in place; it is either formed in concrete or consists of a metal insert.

Ridge: The horizontal line where two opposite sloping sides of a roof join at the highest point of the roof, hip, or dormer. On double sloped gable roofs sometimes called the comb.

Ridge Cap: Formed shingles, shake or tile used to cover the ridge of a building. Make sure that specially designed cap products are used. Many roofers will use materials not made for this purpose.

Rise: The vertical distance from the eaves line to the ridge.

Roll Roofing: Any roofing material, which comes from the dealer in rolls. More specifically it applies to mineral surfaced asphalt, or composition roofing.

Roll Roofing (granule surfaced): Roll roofing finished on one side with colored granules.

Roll Roofing (smooth surfaced): Roll roofing which is coated on both sides with either a smooth or veined surface.

Roof System: A system of interacting roof components, generally consisting of a membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building’s thermal resistance.

Roof: A protective covering that covers or forms the top of a building.

Roof Drain: The termination or fitting at the roof of an interior drain or leader for draining rainwater from normally flat roofs.

Roof Insulation: Any medium or low density material used as part of the roofing system to reduce heat loss through the roof. A variety of insulation materials are being used including wood fibers, glass fibers, cork, plastics and poured lightweight.

Roof Span: Distance from outer wall to opposing outer wall of a building covered with a roof.

Run: The horizontal distance between the face of a wall and the ridge of the roof.

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S
Saturated: Soaked or filled with moisture. A core sample of an existing assembly is considered saturated when droplets of moisture can be squeezed from the sample.

Scupper: An outlet in the wall of a building or a parapet wall for drainage of overflow water from a floor or roof directly to the outside. Special scupper drains connected to internal drains are also sometimes installed at roof and wall junctions.

Self-Healing: A term used in reference to bitumen which melts with the heat from the sun's rays, and seals over cracks that earlier formed in the bitumen from other causes.

Self-Sealing Cement: 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 cooler seasons, sealing time depends on the temperature and amount of direct sunlight hitting the shingles. Hand sealing with plastic cement should be done to ensure sealing in winter.

Selvage: That portion of roll roofing overlapped by the succeeding course to obtain double coverage.

Separator: Term used to describe the means of keeping two non-compatible materials from coming into contact with each other.

Side Lap: The horizontal distance one shingle overlaps adjacent shingle in the same course; also the horizontal distance one sheet of roofing overlaps adjacent sheet.

Single Coverage: Method of applying roof shingles to provide only one complete layer of roof protection. Many special shingles for re-roofing are designed for single coverage for reasons of economy.

Single-Ply Membranes: Roofing membranes that are field applied using only one layer of membrane material (either homogeneous or composite) rather than multiple layers.

Skirt: Membrane material attached to an accessory, such as curbs, stacks, drip edge, gravel stop, drains etc. The skirt is used for overlapping onto a deck sheet for the purpose of field welding a watertight assembly. Standard skirts are 6” but can also be ordered larger.

Sky Light: Glass opening in roof to admit light.

Soffit: A board or sheet that extends from the fascia to the buildings siding and hides the bottom of an overhang. Soffit may or may not contain ventilation slots depending on the attic venting system used.

Square: A unit of roof measure covering 100 square feet.

Starter Course: The first course of shingles installed on a roof, starting at the lower left edge of the eave.

Step Flashing: Metal shingles or plates used in a stair-step pattern under regular shingles. Step flashing is the recommended flashing whenever a wall or chimney is above the roof line.

Strip Mastic: ¾” wide butyl tape used for back seal only. Available in cases of 10 rolls, 350’ total.

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T
Tab: Weather exposure surface of a shingle between the cutouts.

Tack Claw: A tool used to check field seams for proper welding.

Termination: The method of anchoring and/or sealing free edges of the membrane in a roofing or waterproofing system.

Termination Bar: is a ridged, extruded vinyl termination bar and shall be fastened 6" on center to the deck or wood nailer with approved fasteners. Termination bar may be used as perimeter detail and as termination on any square or rectangular penetration.

Thermoplastic: Type of single-ply membrane that can be heat welded and includes a re-enforcement layer of polyester (scrim), which provides increased strength. Thermoplastic membranes are light in color and will usually result in energy savings.

Three-Dimensional Shingle: See laminated shingles.

Three-Tab Shingle: The most economical shingle manufactured, usually 12” x 36” in size with three tabs.

Tie-In: The transitional seal used to terminate roofing or waterproofing application at the top or bottom of flashings or by forming a watertight seal with the substrate, membrane, or adjacent roofing or waterproofing system.

Truss: A combination of members such as beams, bars and ties, usually arranged in triangular units to form a rigid framework for supporting loads over relatively long spans as in wide span roof construction.

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V
Valley: The horizontal line formed along the depressed angle at the bottom of two inclined roof surfaces.

Vapor Barrier: A material that prevents the passage of water or water vapor through it.

Velux: One of the world leaders in skylight manufacturing. Uses all glass skylights instead of plastic bubbles that are common in the industry today.

Vent: An outlet for air; vent pipe in a plumbing system; a ventilating duct.

Vent Pipe: A vertical pipe providing an escape for foul gasses from a sanitary fixture. For a number of fixtures the vent pipes lead into a larger vertical pipe to the outside through the roof called a vent stack.

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W
Walkway Pads: A non-skid walkway pad for rooftop protection in heavily traveled areas such as around large units that require service.

Waterproof: The quality of a membrane, membrane material, or other component to prevent water entry.

Wind Load: Force exerted by the wind on a structure or part of a structure.

Water Vapor: Moisture as a gas in air. Warm air can hold more water vapor than cold air. Water vapors in the air crates a pressure much like any other gas. Cold air has a relatively low vapor pressure.

Wind Uplift: The force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface.

Wrinkle: A slight ridge caused by folding, rumpling or creasing. In roofing usually refers to the common wrinkle pattern that forms over the joints or insulation.

Wood Nailer: #2 grade lumber or better is required as a hard surface for edge fastening in any situation where 1-inch or greater of insulation is added to the roof perimeter edge. 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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