Roofing 101 - Roofing Terms, Definitions and Conditions


*Aggregate: Crushed stone, slag or water-worn gravel that comes in a wide range of sizes. Used to surface built-up roofs.

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

Area Divider: A flashed assembly usually extending above the surface of the roof that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas, sometimes referred as a control joint.

Asphalt Shingles: Composition roof shingles made from asphalt-impregnated felt covered with mineral granules.

Ballest: Weight used to protect single-ply roofs or to prevent blow off of systems which are not adhered.

Bare spots: Small areas on a roof where the top membrane has become exposed to the elements.

*Base Flashing: 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. 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.

Batten: Pressure treated wood ¾” thick, 2” wide, 4’ long. Nailed to roof deck to hold certain kinds of tile.

Blister: Bubbles that may appear on the surface as asphalt roofing after installation.

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

Buckling: Warping or wrinkling of the roof membrane.

Building Code: Published regulations and ordinances established by a recognized agency prescribing procedures, and construction details for structures. Applying to designated jurisdictions(city codes) Building codes control design, construction, and quality of materials, use, etc.

*Built Up Roof: Roof composed of multiple layers of asphalt felt laminated with cold tar, pitch or asphalt with a top layer of crushed slag or gravel. Normal issued on flat roofs or those with very slight slope.

Cant Strip: A beveled support used at the intersection of the roof deck with vertical surfaces so that bends in the roofing membrane to form base flashings can be made without breaking the felts.

Cap Flashing: The Portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing; sometimes referred to as counter flashing.

*Cap Sheet: Granule-surface coated sheet used as the top ply of some built-up modified bitumen roof flashing.

*Caulking/ Sealants: Adhesive sealant used to fill in small areas against water. le: Around windows in a long bead so water won’t leak in. Sold in tubes, and applied by pressure. Normally by hand with a ‘caulking gun’.

Clearstory: The uppermost area of a roof plane that drops off without intersecting with another roof plane.

Collar: Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe called a vent sleeve. Sometimes referred as boot.

Conductor: A pipe for conveying rain water from the roof gutter to a drain, or from a roof drain to the storm drain; also called a leader, downspout, or downpipe.

Coping: A construction unit placed at the top of the parapet wall to serve as a cover for the wall.
Counter flashing: Strips of metal, roofing, or fabric inserted and securely anchored to the regle and/or attached to a vertical surface above the plane of the roof and turned down over the face flashing to protect the base flashing.

*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.

Cricket: A peaked saddle construction at the back of a chimney to prevent accumulation of snow and water around the chimney.'

Deck: The surface installed over the supporting framing members {trusses}, to which the roofing material is applied.

Degranulation: The removal of granules from the shingles’ exposed surface causing premature aging and deterioration.

Diverter: Used to direct water.

Downspout: A pipe for draining water from the gutters; sometimes, called a “leader”.

Drip edge: A corrosion-resistant, non staining material used along the eaves and rakes to allow water run-off to drop clear of underlying decking and/or fascia.

Dry lap: A term describing the absence of bitumen between the piles of felt at the overlap in a BURM.

Eave: The horizontal roof overhang that extends outward and is not directly over the exterior walls or the buildings interior.

*Edge metal: A term relating to brake or extruded metal around the perimeter of a roof.
Exhaust Ventilation: Air that is typically vented or exhausted from the roof cavity, typically through near the ridge.

Expansion joint: A device used to make up the motion of expansion and contraction. On large roofs this provision for the movement of the materials forming the walls, roof deck and roof covering is usually made by deliberately separating the building into sections, and covering separation between adjacent sections with the expansion joint to allow movement but keep out the weather. Expansion joints, unlike control joints, penetrate through the roof deck.

Exposure: The portion of the roofing material exposed to the weather, after installation.

Facade: The front of a building. Frequently, in architectural terms an artificial or decorative effort.

*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.

Flashing: Metal strips, used to prevent water seepage, and installed around chimney, vents, windows, doors, and skylight, along seams in the roof and beneath shingles. The purpose of flashing is to prevent the penetration of water as well as to provide a drainage passageway between joints, most commonly the joint between a roof and a well. Also see metal flashing.

Flashing Base: The upturned edge of the watertight membrane formed at a roof termination point by the extension of the felts vertically over the cant strip and up the wall for a varying distance where they are secured with mechanical fasteners.

Flat or low slope: Pitch of less than three (3) feet of rise over twelve (12) feet of run is considered a flat or low slope roof. Installation of composition roofing, at this minimum slope, is not recommended and can leak due to blow back.

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.

Fishmouth: A characteristic opening at the exposed lap edge of BUR felts due to loss of bond or wrinkling of the felt.

FRSA - Florida's Association of Roofing Professionals
Florida Roofing, Sheet Metal & Air Conditioning Contractor's Association

Gable: A triangular-shaped portion of the end wall of a building directly under the sloping roof and above the eave line.

Grout: A mixture of cement, sand and water used to fill cracks and cavities in masonry

Gutter: The trough that channels water from the eaves to the downspouts.

Header: The beam into which the common joists are fitted when framing around a roof opening.

Hip: The angle formed by the intersection of two sloping roof planes.
Ice and Water Shield: A layer of waterproofing installed under the shingles at a roof’s perimeter, valley ridges.

Impact Resistant: The Ability of a roofing material to resist damage (e.g. puncturing from falling objects (tree branches and hail), application equipment, foot traffic, etc. The impact resistance of the roofing assembly is a function of all of its components, not just the membrane itself. This product offers homeowners an insurance reduction.

Insulation: Any of a variety of materials designed to reduce the flow of heat, either through vents typically installed in the soffit or eave of a roof.

Lap: To cover the surface of one shingle or roll with another.

Leads: See Plumbing Vent Jack, Lead boot, Lead flashings.
Low slope Application: Method of installing asphalt shingles {or other material}, on slopes between 2 and 4 inches per foot. Involves decreasing the amount of material exposure {to the weather}, and by increasing the ply of underlayment.

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. Contains no gables.

Membrane: A flexible or semi-flexible material, which functions as the waterproofing component in a roofing or waterproofing assembly, and whose primary function is the exclusion of water.

*Metal Flashing: Accessory components fabricated from sheet metal and used to weatherproof terminating roof covering edges. Frequently used as though-wall flashing, cap flashing, counter-flashing, step-flashing, etc.

Mineral surfaced roofing: Asphalt shingles, roll roofing and torch down that are covered with granules.

Modified Bitumen: Composite sheets consisting of polymer modified bitumen often reinforced and sometimes surfaced with various types of mats, films, foils, and mineral granules.

Nailer: A piece of lumber secured to non-nailable decks and walls by bolts or other means, which provides a suitable backing onto which roof components may be mechanically fastened.

*NRCA: National Roofing Contractors Association

*Parapet : A low wall along the edge of and surrounding a roof deck. It is generally an extension of exterior building walls and above firewalls that usually extend about a meter or less above the roof.

Penetration: Any object passing through the roof.

Pipe boot or jack: See plumbing vent jack.

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 an 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.

Plumbing Vent jack: Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. Made of lead, rubber or metal. Referred to by various terms {pipe boot/jack, plumbing boot/jack and/or no-caulk or leads}.

Ponding: The excessive accumulation of water at low-lying areas on a roof.

Projection: Any object or equipment which pierces the roof membrane.

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

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

Re-roofing: The process of tearing off and replacing an existing roof system.

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.

Ridge vents: One of many products located at the ridge that allows the escape of warm and/or moist air from the attic or rafter cavity.

Roof: The assembly of interacting components designed to weatherproof and normally to insulate a buildings surface, separated from adjacent assemblies by walls or changes in elevation. ROOF COATING – Compatible roofing material that can be brushed, rolled or sprayed to a roof surface. Roof coating is often used in maintenance and restoration.

Roof deck: That component in building construction, which forms a platform on which the remainder of the BURM components are placed.

Roof drain: The termination or fitting at the roof of an interior drain or leader, for draining water from nominally flat roofs. Inside Drain: A roof drain positioned on a roof at some location other than the perimeter. It drains surface water inside the building through closed pipes to a drainage system.

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 system: General term referring to the waterproof covering, roof insulation, vapor barrier, if used and roof deck as an entity.

Self-Adhering: A membrane that can adhere to a substrate and to itself at overlaps without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane form bonding to itself during shipping and handling.

Scrim: A woven or mat-type fabric that is used as a membrane sandwich between other material to provide reinforcement and stretch resistance.

Sheathing: The boards of sheet type material, plywood or asphalt saturated sheets, nailed to studding or roofing rafters as the base for application of the roof covering.

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 ply: A descriptive term signifying a roof membrane composed of only one layer of material such as EPDM, Hypalon or PVC. TPO “Elvaloy”

Skylight: A structure on a roof that is designed to admit light and is somewhat above the plane of the roof surface.

SMRSA - Sarasota Manatee Roofing & Sheet Metal Contractors Association

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.

Soil stack: A vent pipe that penetrates the roof deck.

Splitting: The formation of long cracks completely through a roof membrane. Splits are frequently associated with lack of allowance for expansion stresses. They can also be a result of deck deflection or change in deck direction.

Standing seam: A type of joint often used on metal roofs.

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.

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

*Tear off: A term used to describe the complete removal of the built up roof membrane and insulation down to and exposing the roof deck.

Torching: Applying direct flame to a membrane for the purpose of melting, heating or adhering.

Turbine: Air flow device used to ventilate attic areas. Mounted on the roof and driven by the wind.

Underlayment: A layer of asphalt saturated {sometimes referred as tarpaper} which is installed over deck before shingles are installed, which provides additional protection for water intrusion.

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.

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 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.

Weep hole: A hole which allows for drainage of entrapped water from masonry structures.