Glossary

Aggregate: Crushed or smooth rock, crushed slag, or water-worn gravel to surface flat or low-slope roots and to provide ballast for floating membranes. (Specifications for single-ply roofing systems usually prohibit the use of crushed rock or slag aggregate unless it is installed over a layer of cushioning material.)

Asphalt. A brownish-black, natural petroleum residue used in applying roofing.

Ballast. Aggregate, concrete pavers, or other material used to prevent wind uplift of a loose-laid single-ply roofing system. Old tires are sometimes used as temporary ballast during the installation of the membrane.

Base coat. The first coat of adhesive in a built-up roofing system; also, the multiple coats of base waterproofing material in a fluid-applied single-ply roofing system, usually followed by one or more protective topcoats of a more weather-resistant material.

Batten. A narrow reinforcing strip, usually made of metal, used to secure a single-ply roofing membrane at parapet watts, curbs, and other locations where the membrane terminates or turns up at an angle change. Battens are also used in some mechanically fastened single-ply roofing installations to secure the membrane in the field area..

Bitumen. Coal tar pitch or asphalt.

Brace. A piece of wood or other material that holds anything tightly or supports it firmly; a prop.

Building Code. Governmental rules and regulations for building construction, which in most California cities is the latest Edition of the California Building Code, including local amendments.

Built-Up. A roof formed by a number of layers of roofing mopped together with hot asphalt or pitch.

Cant strip. A bevelled strip of wood, wood fiber., or other material installed in the angle where a root deck adjoins a parapet wail, curb, or other vertical structure. The 45-degree bevel of the cant strip permits the roofing membrane or base flashing to make a smooth transition from the horizontal to the vertical..

Cantilever. A projecting beam supported at only one end.

Cap sheet. A finish roofing material used as a covering for a roof.

Caulk. To make watertight by plugging with mastic. Chalk line. A heavy string or cord used for lining purposes.

Cleat. A strip of wood or metal fastened across other
Coal-tar pitch. A thick dark liquid obtained by distillation of soft coal; used for roofing and waterproofing.

Coating liquid. A liquid with an asphalt or coal-tar base used for preserving roofs.
Condensation. The conversion of water vapor to water as the temperature drops or the atmospheric pressure rises. Heavy condensation on the underside of a roof may give the appearance of a leak.

Coping. The top covering of a wall; may be metal., tile, masonry, or wood.

Core sheet. A reinforcing sheet of polyethylene plastic sandwiched between the bitumen layers in some modified bitumen single-ply membrane materials; also called a "carrier sheet."

Cornice. A horizontal molded projection at the top of a building; also the plastered underside of the eaves,

Counter-flashing. Flashing that extends over another flashing. Also called cap flashing.

Course. A continuous row or layer of shingles or other roofing material.

Coverage. The area covered by a given quantity of roofing material, with an allowance made for lapping.

Cricket. A superimposed structure installed in a roof area, for example behind a chimney, to divert water and assist drainage. Also called a saddle.

Cupola. A hemispherical roof.; a small structure above the roof.
Curb. A base for a skylight, hatch, or rooftop mechanical equipment; usually constructed of lumber

Cured. Completely dry; moisture free.

Curing agent. The part B component in a two-part synthetic fluid-applied roofing or waterproofing material that chemically solidifies the part A component; also, a coating applied to fresh concrete to retain moisture and, thus, aid curing.

Cutback. Asphalt dissolved into its liquid form.

Cutout. The narrow slot between the tabs of an asphalt strip shingle.

Dead load. The weight of all materials and fixed equipment incorporated into the building such as those loads imposed on a roof structure by air-conditioning units, other permanent rooftop equipment, the roof system, and the roof deck-. (See live load.)

Deck. The structural surface on which the roofing or waterproofing system is applied. (See roof system.)

Delamination. Separation of the plies in a plywood panel or a built-up roofing membrane, also, Separation of the insulation material in an insulation board.

Dormer. A vertical protrusion rising from a sloping roof, such as a minor structure containing a window.

Double Coverage Roofing. Shingles or roll roofing applied with sufficient overlap so that no part of the deck is covered with less than two layers of roofing. Double-coverage roll-roofing material is called split sheet or 19-inch (48.3 centimeter) selvage.
Dry rot. Wood decay caused by a fungus that consumes the cellulose portion of the wood, leaving a soft skeleton that readily crumbles to a powder. Wood structures that are inadequately ventilated and constantly exposed to moisture are especially vulnerable to dry rot.

Eaves. The projecting lower edge of a roof..

Elastomer. A synthetic material that has rubber-like properties. Elastomeric roofing and waterproofing materials are marketed as fully or partly cured roll sheeting or as fluids that cure after application to become tough, elastic membranes.

Elastoplastics.. A general term for all synthetic roofing and waterproofing materials.
Expansion joint. A planned structural separation between two adjoining sections of a deck, wall, or floor that relieves stresses resulting from building movements and thermal expansion and contraction.

Felt.. The general term for all ply materials used in built-up roofing and waterproofing systems. Felts are manufactured from organic materials, such as vegetable fibers; from mineral fibers, such as asbestos; or from glass fibers. They may be saturated (with soft bitumen) or unsaturated; coated (with harder bitumen) or uncoated; or impregnated with resin.

Firewall. A wall erected above the roof to block fires between sections of the building.

Flash point. The temperature at which asphalt or tar, when slowly heated, gives off vapors that will ignite upon the application of a flame.

Flashing cement (mastic). A trowel-grade cement used alone or in conjunction with fabric reinforcement where flashing is required.

Flashing. The system used to seal the edges of a roofing or waterproofing membrane at walls, curbs, expansion joints, gravel stops, drains, pipes and other projections, and wherever else the membrane is interrupted or terminated. Base flashing covers the edge of the membrane at walls, curbs, and other vertical intersections; cap flashing or counter-flashing protects the turned-up edge of the base flashing.

Floating membrane. A single-ply roofing membrane that is fastened to a flat or low-slope deck only at the perimeter and other terminations and is held down by rock or gravel ballast; also called a loose-laid membrane.

Flue. A channel or passage for smoke or gases of combustion; a chimney.

Flush. A term applied to surfaces that are level and form a single unbroken surface,

Gable roof. A ridged. double-sloping roof.

Gambrel roof. A gable roof with its slopes broken by an obtuse angle; a gable roof with two pitches in one field.

Gravel stop. A flanged barrier, usually formed of sheet metal that is installed around the perimeter of an aggregate-surfaced roof to retain the aggregate and to weatherproof and finish the roof's edge.

Hip roof . A roof having sloping ends, thus four sloping sides. The line where adjacent sloping sides meet is called a hip.

Joist. A horizontal timber to which the boards of a floor or lath on a ceiling are fastened.

Kettle. A metal vessel for heating asphalt or coal-tar pitch.

Live load. The load imposed on a roof by workers and their equipment, may also include wind, rain, snow, and ice toads. (See dead load.) materials for additional strength; may be nailed against the wall for supporting an object

Matting strip. A strip of wood set in concrete along the eaves or gable of a roof.

Mission tile. A curved tapering tile unit.

Modified Bitumen. Asphalt or coal-tar pitch compounded with a synthetic polymer to produce a bituminous material with superior toughness, elasticity, weathering ability, and resistance to temperature extremes.

Molding. A cornice or projecting decorative member used on any pan of a building.

Nailer. A length of treated lumber installed at the edge of a deck and around projections to provide anchorage for the roofing membrane. In a poured concrete deck or wall, the nailers may be embedded in the concrete.
of workers and materials during the construction of a building.

Parapet. A low wall above the roof level.

Penetration, A pipe, vent stack, column, or similar piece that extends up through a deck.

Perlite. Expanded volcanic glass used as an insulating aggregate in some types of lightweight concrete and as the principal component in some insulation boards.

Pitch pocket. A flanged, metal container installed around a column or other penetration on a roof and filled with bitumen or plastic cement to seal the penetration.

Pitch, The slope of a roof, indicated by the relation of the rise to the span; also a coal4ar roofing material.

Plastic. Waterproofing mated al, composed of coal tar, asphalt, asbestos fibers, and so on,

Plasticizer. A modifier added to a. synthetic polymer to facilitate processing and to give the finished product increased flexibility and toughness.

Ply. A layer of felt in a built-up roofing or waterproofing membrane.

Ponding. Accumulation of water on a flat or low-slope roof usually due to plugged drains or excessive deflection of the deck.

Pot life. The length of working time available before a container of single-ply adhesive or fluid rooting material that has been opened and stirred or combined with a curing agent begins to set up.

Rake. The slope of a roof; the sloping edge on a gable roof that may be covered with a barge board, or verge board.

Reglet. A groove in a parapet wall or other vertical surface adjoining a roof deck; used in attaching a flashing strip or counter-flashing.

Ridge. The point on a double-sloping roof at which the rafters meet the ridge pole,

Rise. The vertical height of the top of a roof above the plate line, or tile increase in height of a rafter per foot of run.

Roof system. A system of interacting roof components (not including the deck) designed to weatherproof and normally to insulate the top surface of a building.

Roofjack. A flashing device, made of sheet metal or molded plastic, used to cover a pipe or a vent stack on a roof (also called a pipe jack); also, a bracket used to support a scaffolding plank on a. steep roof.

Rotor welder. An automatic lap-welding machine.

Run. Usually one-half the distance of the span of a roof.

Scrim. Woven polyester or fiberglass fabric reinforcement embedded in many types of single-ply membrane materials.

Separation sheet. A protective layer of kraft paper, metal foil, or other material installed between a. single-ply membrane and a chemically incompatible substrate (for example, between a PVC membrane and an existing bituminous membrane); also called a divorcing sheet.

Shake. A rough. unshaved wood shingle.

Sheathing. The boards or other material used for covering the frame or roof structure.

Shelf life. The length of time that an adhesive or a fluid roofing material can be stored in its unopened container,

Softening point. The temperature at which bitumen becomes soft enough to flow.

Solvent wash. Solvent used to clean the lap-joint mating surfaces in a single-ply membrane before the laps are sealed; also called splice wash or lap wash.

Span. A space or distance between supports; in roof framing, the width of the frame between the outside edges of the building.

Specifications. Written information augmenting the plans of a building.
sphere, terminated at the boundary thereof.

Square. A roof area of 100 square feet (9.3 square meters).

Substrate. The surface on which the roofing or waterproofing membrane is placed (i.e., the deck or insulation).

Thermoplastic. A nonvulcanized plastic that. can be repeatedly heat-softened and reshaped.

Thermoset. A vulcanized elastomer.

Valley. The guner or angle formed by the meeting of two roof slopes.

Vapor retarder. Sheet material designed to restrict the passage of water vapor through a wall or roof; improperly called a vapor barrier.