Aggregate: crushed stone, crushed slag, or water-worn gravel used for surfacing a built-up roof, any granular mineral material.

Alligatoring: the cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks  similar to an alligator’s hide; the cracks may or may not extend through the surfacing bitumen.

Asbestos: a group of natural, fibrous, impure silicate materials.

Asphalt: a dark brown to black cementitious material in which the predominating constituents are bitumens, which occur in nature or are obtained in petroleum processing.

Blister: a spongy raised portion of a roof membrane, ranging in area from 1 inch in diameter and of barely detecable height upwards Blisters result from the pressure buildup of gases entrapped in the membrane system. These gases most commonly are air and/or water vapor.  Blisters usually involve delamination of the underlying membrane piles.

Built-Up Roof Membrane: a continuous, semi-flexible roof membrane assembly, consisting of plies of saturated felts, coated felts,fabrics or mats between which alternate layers of bitumen are applied, generally surfaced with mineral aggregate,bituminous materials, or a granule surfaced roofing sheet.

Cant Strip: a bevelled shaped strip of wood or wood fiber that fits into the angle formed by the  intersection of a horizontal surface and a vertical surface. The 45 degree slope of the exposed surface of the cant strip provides a gradual angular transition from the horizontal surface to the vertical surface.

Cap Sheet: a granule-surfaced coated sheet used as the top ply of a built-up roof membrane or flashing.

Caulking: a composition of vehicle and pigment, used at ambient temperatures for filling joints, that  remains plastic for an extended time after application.

Condensation: the conversion of water vapor or other gas to liquid as the temperature drops or the atmospheric pressure rises.

Coping: the covering piece placed on top of a wall that is exposed to the weather. It usually sloped to shed water.

Cornice:Overhang of a pitched roof at the eave line, usually consisting of a facia board, a soffit for a closed cornice, and appropriate moldings.

Crack: a separation or fracture occurring in a roof membrane or roof deck, generally caused by thermally induced stress or substrate movement.

Dormer: an opening in a sloping roof, the framing of which projects out to form a  vertical wall suitable for windows or other openings.

Downspout: a pipe, usually of metal, for carrying rainwater from roof gutters.

Drain: a device that allows for the flow of water from a roof area.

Facia: a flat board, band, or face, used sometimes by itself but usually in combination with moldings, often located at the outer face of the cornice.

Fishmouth: a half-cylindrical or half-conical opening formed by an edge wrinkle; in shingles, a half-conical opening formed at a cut edge.

Flashing: the system used to seal the edges of a membrane at walls, expansion joints, drains, gravel stops, and other areas where the membrane is interrupted or  terminated. Base flashing covers the edges of the membrane. Cap flashing or counterflashing shields the upper edges of the base flashing.

Gutter: a shallow channel or conduit of metal or wood set below and along the eaves of a house to catch and carry off rainwater from the roof.

Hip: the external angle formed by inclined planes from all four sides of a roof.

Hip roof: a roof that rises by inclined planes from all four sides of a building.

Insulation: a material applied to reduce the flow of heat.

Lintel: a horizontal structural member that supports the load over an opening such as a door or window.

Masonry: stone, brick, concrete, hollow-tile, concrete-block, gypsum-block, or other  similar   building units or materials of a combination of the same, bonded together with mortar to form a wall, pier, buttress, or similar mass.

Mineral-Surfaced Roofing: built-up roofing materials whose top ply consists of a granule-surfaced sheet.

Pitch Pocket: a flanged, open-bottomed, metal container placed around columns or other   roof penetrations that is filled with hot bitumen and/or flashing cement to seal the joint.

Pond: a roof surface which is incompletely drained.

Reroofing: the practice of applying new roofing materials over existing roofing materials.

Ridge: the horizontal line at the junction of the top edges of two sloping roof surfaces.

Roll Roofing: the term applied to smooth-surface or mineral-surfaced coated felts.

Roofer: the trade name for the workman who applies roofing materials.

Shingle: a small unit of prepared roofing material designed to be installed with similar units in overlapping rows on inclines normally exceeding 25%; to cover with shingles; to apply any sheet material in overlapping rows like shingles.

Soffit: usually the underside of an overhanging cornice.

Split: a separation in roofing material resulting from movement of the substrate.

Square: the term used to describe 100 square feet of roof area.

Substrate: the surface upon which the roofing or waterproofing membrane is applied.

Tar: a brown or black bituminous material, liquid or semi-solid in consistency, in    which the predominating constituents are bitumens obtained as condensates  in the processing of coal, petroleum, oil-shale, wood, or other organic materials.

Valley: the internal angle formed by the junction of two sloping sides of a roof.

Vent: an opening designed to convey water vapor or other gas from inside a building or a building component to the atmosphere, thereby relieving vapor pressure.

Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.