The Language of Roofing from A to Z
Below is a list of some of the most frequently used roofing terms to help you understand your roofing system and the installation or repair process.
Absorption: How a material accepts gases or liquid, such as moisture.
Aggregate: Materials such as rock, stone, crushed stone, crushed slag, or marble chips used for surfacing or as a ballast in a roof system.
Alligatoring: The appearance of cracks on the surface of bitumen on a built-up roof; similar appearance to the skin of an alligator.
Aluminum: A non-rusting metal typically used for residential cladding
Apron flashing: A term used for a flashing that is situated at the juncture of the top of the sloped roof and a vertical wall or steeper-sloped roof.
Architectural shingle: A shingle design that appears three-dimensional.
Asphalt: A dark brown or black substance that is a by-product of the oil refining process and can also be found naturally.
Asphalt emulsion: Asphalt particles mixed with an emulsifying agent such as bentonite clay and water.
Attic: The space above a ceiling and below a roof.
Ballast: An anchoring material, such as aggregate or precast concrete pavers, held in place by the force of gravity.
Base flashing (membrane base flashing): Plies or strips of roof membrane material used to close off and/or seal a roof at the roof-to-vertical intersections.
Base ply: The lowest ply of roofing in a roof membrane or roof system.
Bitumen: A material typically composed of asphalt or coal tar.
Blackberry (sometimes referred to as Blueberry or Tar-Boil): A small bubble or blister in the flood coating of an aggregate-surfaced, built-up roof membrane.
Blister: An enclosed pocket of air which may be mixed with water or solvent vapour, trapped between layers of felt or membrane; many also appear between the membrane and substrate.
Blocking: Sections of wood built into a roof assembly, usually attached above the deck and below the membrane or flashing.
Buckle: A displacement of a roof membrane in an upward direction; usually appears over insulation or deck joints.
Built-Up Roof Membrane (BUR): A continuous, semi-flexible multi-ply roof membrane consisting of plies or layers of saturated felts, coated felts, fabrics, or mats between which alternate layers of bitumen are applied.
Butt flashing: Covers or shields the upper edges of membrane base flashing, wall flashing, or primary flashing.
Barrel roof: A roof configuration with a partial cylindrical shape to it.
Base ply: The primary ply of roofing material in a roof system.
Base sheet: An asphalt-impregnated, or coated felt used as the first ply in some built-up and modified bitumen roof systems.
Batten: A strip of wood usually fastened to the structural deck for use in attaching a primary roof system such as tile.
Birdstop: Barrier placed under the lower course of round Spanish type tile, to keep birds from making nests in the roof.
Boot: A piece of material preformed to protect roof penetrations from dirt, moisture and other foreign and/or damaging substances.
Buckle: A long, tented displacement of a roof membrane can occur over insulation and deck joints.
Built-in gutter: A rain gutter built into the roof eave and supported by the roof structure.
Cap sheet: A granule-surface coated sheet; typically employed as the top ply of some built-up or modified bitumen roof membranes and/or flashing.
Caulking: The process used to seal a joint or juncture.
Cladding: The material used on a building’s exterior wall enclosure.
Cleat: A metal strip, plate or metal angle piece, used to secure two or more components.
Coating: A layer of material spread over a surface for protection or decoration.
Composition shingle: A unit of asphalt shingle roofing.
Condensation: The conversion of water vapour or other gas to liquid state as the temperature drops or atmospheric pressure rises.
Coping: The covering piece on top of a wall, which is exposed to the weather usually made of metal, masonry, or stone. It is preferably sloped to shed water back onto the roof.
Copper: A natural weathering metal used in metal roofing.
Caulk: A material with no elastomeric properties used for sealing joints.
Cladding: A material used to cover the exterior wall of a building.
Contact cements: Adhesives used to adhere or bond roofing components.
Coping: The piece of material used to cover the top of a wall and protect it from the elements. It can be constructed from metal, masonry, or stone.
Cornice: The decorative horizontal moulding or projected roof overhang.
Counter flashing: Formed metal sheeting secured on or into a wall, curb, pipe, rooftop unit, or other surface, to cover and protect the upper edge of the membrane base flashing or underlying metal flashing.
Course: Each row of shingles of roofing material that forms the roofing, waterproofing, or flashing system.
Coverage: The surface area covered by a specific quantity of a particular material.
Cross ventilation: When air moves between the vents in a roof cavity.
Curb: A raised member used to support roof penetrations, such as skylights, mechanical equipment, hatches, etc. above the level of the roof surface.
Deck: A structural component of the roof of a building; must be capable of safely supporting the design, dead and live loads including the weight of the roof system, and the additional live loads required by the governing building codes.
Deflection (bowing, sagging): A downward movement of a structural member or system under load.
Delamination: Separation of the laminated layers of a component or system.
Design loads: Those loads specified in building codes or standards published by federal, provincial, county, or city agencies, or in owners’ specifications to be used in the design of a building.
Dome: A roof that is shaped like a half-circle or a variation of one.
Dormer: A framed projection through the sloping plane of a roof.
Double graveling: The process of applying two layers or flood coats of bitumen and aggregate to a built-up roof.
Downspout: A conduit used to carry runoff water from a scupper, conductor head, or gutter of a building to a lower roof level.
Drain: The device that collects and directs the flow of runoff water from a roof area.
Drip edge: A metal flashing, or other overhanging component, with an outward projecting lower edge.
Dynamic load: A non-static load such as a wind load or a moving person.
Eave: Edge of a roof that extends beyond the supporting wall.
Expansion Joint: A structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.
Extrusion: The process used to force a material through a “die”.
Eavestrough: Another name for a gutter.
Eyebrow: A small, shed roof protruding from the main roof or located on the side of a building below the level of the main roof.
Fascia: A vertical or steeply sloped roof or trim, typically located at the perimeter of a building.
Felt: A flexible sheet manufactured by the interlocking of fibres through a combination of mechanical work, moisture and heat.
Flange: The projecting edge of a rigid or semi-rigid component, such as a metal edge-flashing flange, skylight flange, flashing boot, structural member, etc.
Flash point: The lowest temperature of a liquid at which it gives off vapours sufficient to form an ignitable mixture with air near its surface.
Flashing: Components used to weatherproof or seal the roof system edges at perimeters, penetrations, walls, expansion joints, valley, drains, and other places where the roof covering is interrupted or terminated.
Gable: A triangular portion of the end wall of a building directly under the sloping roof and above the eave line.
Galvanized steel: Steel coated with zinc for corrosion resistance.
Granule: A small aggregate, naturally or synthetically coloured, used to surface cap sheets, shingles, and other granule-surfaced roof coverings.
Gutter: A channelled component installed along the down slope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.
Hip: The inclined external angle formed by the intersection of two sloping roof planes.
Ice dam: An accumulation of ice that forms when a roof surface transitions from warm to cold, often caused by refreezing of melting ice at the overhang of a steep roof.
Interlocking shingles: Individual shingles that mechanically attach to each other to provide wind resistance.
Joist: Metal or wood beams arranged parallel from wall to wall to support a building’s floor, ceiling or roof.
Live loads: Temporary loads that the roof structure must be designed to support, as required by governing building codes. Snow and rain are typical examples of live loads.
Membrane: A flexible or semi-flexible material which functions as the waterproofing component in a roofing or waterproofing assembly; its primary function is the exclusion of water.
Metal flashing: Metal accessory components used to weatherproof terminating roof covering edges.
Modified bitumen: Bitumen modified through the inclusion of one or more polymers.
Organic: Comprised of hydrocarbons or their derivatives originating from plant or animal matter.
Organic felt: An asphalt roofing base material manufactured from cellulose fibres.
Organic shingle: An asphalt shingle reinforced with material manufactured from cellulose fibres.
Parapet wall: That part of a perimeter wall immediately adjacent to the roof which extends above the roof.
Rafter: Sloped structural members, typically extending from the ridge or hip to the down slope perimeter or eave.
Rake: The sloped edge of a roof at or adjacent to the first or last rafter.
Ridge: Highest point on the roof.
Roof assembly: An assembly of interacting roof components (i.e. roof deck, vapour retarder, insulation, and roof covering).
Roof slope: The angle of a roof’s surface.
Run: The horizontal dimension of a slope.
R-Value: The measure of a material’s resistance to heat flow. The higher a material’s R-value, the more it insulates.
Self-sealing shingle: An asphalt shingle that is manufactured with a strip or spots of heat-sensitive adhesive positioned to adhere to the overlying shingle.
Shingle: Roofing material installed in overlapping rows or courses.
Shingling: The application of shingles.
Skylight: A roof accessory designed to admit light into a living space.
Slate: A hard rock consisting mainly of clay minerals.
Slope: The angle of incline, usually expressed as a ratio of rise to run.
Snow guard: A series of devices designed to hold snow in place and prevent sudden snow or ice slides from the roof.
Snow load: A load imposed on buildings or other structures by a snowfall.
Soffit: The enclosed underside of any exterior overhanging section of a roof eave.
Standing seam: A metal roof system that consists of an overlapping or interlocking seam, which occurs at an upturned rib.
Starter course: The first layer of roofing applied along a line adjacent to the down slope perimeter of the roof area.
Static load: Any load that does not change.
Substrate: The surface upon which the roofing or waterproofing membrane is applied.
Tab: The exposed portion of strip shingles and defined by cut-outs.
Underlayment: An asphalt-saturated felt or other sheet material (may be self-adhering) installed between the roof deck and the roof system, usually used in a steep-slope roof construction.
Valley: The internal angle formed by the intersection of two sloping roof planes.
Vapour retarder: Material installed to impede or restrict the passage of water vapour through a roof assembly.
Vent: An opening designed to convey air, heat, or water vapour from inside a building to the atmosphere.