Glossary of Terms

Glossary of Terms

Glossary of Terms

Air barrier

The assembly of materials used in building construction to reduce or retard the uncontrolled passage of air into and out of the building.


A nonrusting, malleable metal sometimes used for metal roofing and flashing.

Apron flashing (Includes illustration)

A term used for a flashing located at the juncture of the top of a sloped roof and a vertical wall, chimney or steeper-sloped roof.

Architectural shingle

See "dimensional shingle."

Asphalt shingle

A shingle manufactured by coating a reinforcing material (paper felt or fiberglass mat) with an asphalt-based coating and having mineral granules on the side exposed to the weather. See "shingle."


The cavity or open space above the ceiling and immediately under the roof deck of a steep-slope roof.

Barrel vault

A building profile featuring a rounded profile to the roof on the short axis but with no angle change on a cut along the long axis.

Base flashing (membrane base flashing)

Plies or strips of roof membrane material used to closeoff and/or seal a roof at the horizontal-to-vertical intersections, such as at a roof-to-wall juncture. Membrane base flashing covers the edge of the field membrane and extends up the vertical surface. See "flashing."

Base ply

The bottom or first ply in a built-up or polymer- modified bitumen roof or waterproofing system when additional plies are to be subsequently installed.

Base sheet

An impregnated, saturated or coated felt placed as the first ply in some low-slope roof and waterproofing systems.


(1) Cap or cover; (2) in a metal roof, a metal closure set over, or covering the joint between, adjacent metal panels; (3) in a steep-slope roof system, a strip of wood or metal usually set in or over the structural deck, used to elevate and/or attach a primary roof covering; (4) in a single-ply membrane roof system, a narrow plastic or metal bar that is used to fasten or hold the roof membrane and/or base flashing in place.


(1) A class of amorphous, black or dark-colored, (solid, semi-solid or viscous) cementitious substances, natural or manufactured, principally composed of high-molecular-weight hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars, pitches and asphaltites; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.

Blanket insulation

Fiberglass or other compressible fibrous insulation, generally available in roll form.


(1) Sections of wood (which may be preservative-treated) built into a roof or waterproofing assembly, usually attached above the deck and below the membrane or flashing, used to stiffen the deck around an opening, act as a stop for insulation, support a curb, or serve as a nailer for attachment of the membrane and/or flashing; (2) wood cross-members installed between rafters or joists to provide support at cross-joints between deck panels.


(1) A covering made of flexible material that may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc., from around a penetration; (2) a flexible material used to form a closure, sometimes installed at inside and outside corners.

Building code

The minimum construction requirements established generally by national organizations and adopted completely or in altered form by local governing authorities. Building code controls design, construction, quality of materials, use and occupancy, location, and maintenance of buildings and structures within the area for which the code was adopted.

Built-up roof (BUR)

A continuous, semi-flexible roof membrane consisting of multiple plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet.

Cap flashing

(1) Usually composed of metal, used to cover or shield the upper edges of the membrane base flashing or wall flashing; (2) a flashing used to cover the top of various buildings components, such as parapets or columns. See "flashing" and "coping."

Cap sheet

A sheet, often granule-surfaced, used as the top ply of some built-up or polymer-modified bitumen roof membranes and/or flashings.


(1) The physical process of sealing a joint or juncture; (2) sealing and making weathertight the joints, seams or voids between adjacent surfaces by filling with a sealant.

Channel flashing

In steep-slope roof construction, a type of flashing used at roof-to-wall junctures and other roof-to-vertical plane intersections where an internal gutter is needed to handle runoff. Commonly used with profile tile.


Stone, masonry, prefabricated metal or wood-framed structure containing one or more flues projecting through and above a roof.


A material used as the exterior wall enclosure of a building.


A continuous metal strip, or angled piece, used to secure metal components. See "clip."


(1) An upward extension of enclosed space created by carrying a setback vertical wall (typically glazed) up and through the roof slope; (2) two intersecting shed roofs on different planes.


A noncontinuous metal component or angle piece used to secure a metal panel to a substrate or two or more metal components together. See "cleat."

Closed-cut valley (Includes illustration)

A method of valley application in which shingles from one side of the valley extend across the valley while shingles from the other side are trimmed back approximately 2 inches from the valley centerline.


(1) A layer of liquid material applied to a surface for protection or appearance; (2) A fluid material applied in the field as a film to the roof surface to provide weather protection to the original roof substrate.(3) a factory- or field-applied protective or decorative layer bonded to its substrate such as a metallic coating deposited mechanically, by hot dipping or electroplating, or a cured paint system application on sheet metal or building surface, or anodized finish on aluminum.


A collection of laws (regulations, ordinances or statutory requirements) adopted by an authority having jurisdiction. See "building code and _model (building) code._


Designed for or capable of being applied without heating as contrasted to hot-applied. Cold-applied materials are furnished in liquid state, whereas hot-applied materials are furnished as solids that must be heated to liquefy before application.


A metal cap flashing around a vent pipe projecting above a roof deck.

Cool roof

A roof system that uses products made of highly reflective and emissive materials for its top surface. Cool roof surfaces can remain at markedly lower temperatures when exposed to solar heat in service than surfaces of roofs constructed with traditional non-reflective roofing products.


The covering piece on top of a wall exposed to the weather, usually made of metal, masonry or stone.


A soft, malleable, naturally weathering metal used in metal roofing or flashing.


The decorative horizontal molding or projected roof overhang.


Vertical wood or metal strips installed on steep-slope roofs over which horizontal battens are secured. The primary roof covering is attached or secured to these horizontal battens.

Counterflashing (Includes illustration)

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.


(1) The term used for a row of roofing material that forms the roofing, waterproofing or flashing system; (2) one layer of a series of materials applied to a surface (e.g., a five-course wall flashing is composed of three applications of roof cement with one ply of felt or fabric sandwiched between two layers of roof cement).

Cover board

An insulation board used over closed cell plastic foam insulation (e.g., polyisocyanurate) to prevent blistering when used in conjunction with hot bituminous membranes. Suitable cover-board insulations are glass-faced siliconized gypsum board, fiberglass board, perlite board, wood fiberboard or mineral fiberboard. Cover boards are also recommended between polyisocyanurate insulation and single-ply membranes to protect the polyisocyanurate.

Cricket (Includes illustration)

A relatively small area of a roof constructed to divert water from a horizontal intersection of the roof with a chimney, wall, expansion joint or other projection.


(1) A raised member used to support roof penetrations, such as skylights, mechanical equipment, hatches, etc., above the level of the roof surface; (2) a raised roof perimeter relatively low in height.


Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.


A structural component of the roof of a building. The deck 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 and provide the substrate to which the roof or waterproofing system is applied. Decks are either noncombustible, (e.g., corrugated metal, concrete or gypsum) or combustible (e.g., wood plank or plywood).

Dormer (Includes illustration)

A structure projecting from a sloping roof usually housing a window or ventilating louver.


A vertical pipe or conduit used to carry runoff water from a scupper, conductor head or gutter of a building to a lower roof level or to the ground or storm water runoff system; also called a conductor or leader.


An outlet or other device used to collect and direct the flow of runoff water from a roof area.

Drip edge

A metal flashing or other overhanging component with an outward projecting lower edge intended to control the direction of dripping water and help protect underlying building components.

Eave (Includes illustration)

The lower edge of a sloping roof; that part of a roof which projects beyond the wall.

Edge venting

The practice of providing regularly spaced or continuously protected (louvered or otherwise shielded) openings along a roof edge or perimeter, used as part of a ventilation system to dissipate heat and moisture vapor.


Ethylene propylene diene M-class rubber, also called ethylene propylene diene terpolymer. See "ethylene propylene diene terpolymer."

Ethylene propylene diene terpolymer (EPDM)

A terpolymer of ethylene, propylene and diene with the residual unsaturated portion of the diene in the side chain to provide for vulcanization. It is a thermosetting synthetic elastomer. EPDM is an acronym for "ethylene propylene diene M-class rubber," which is a name assigned to this material within the classification established in ASTM D1418.

Expansion joint

A structural separation between two building elements that allows free movement between the elements without damage to the roof or waterproofing system.


(1) In steep-slope roofing, a board that is nailed to the ends of a roof rafter; sometimes supports a gutter; (2) in low-slope roofing, the vertical or steeply sloped roof or trim located at the perimeter of a building. Typically, it is a border for a low-slope roof system.


Any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips and bolts, that may be used to secure various components of a roof assembly.


A flexible sheet manufactured by the interlocking of fibers with a binder or through a combination of mechanical work, moisture and heat. Felts are manufactured principally from wood pulp and vegetable fibers (organic felts), asbestos fibers (asbestos felts), glass fibers (fiberglass felts or ply sheets) or polyester fibers.

Fiberglass insulation

Blanket or rigid board insulation composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls.

Fire resistance

The property of materials or their assemblies that prevents or retards the passage of excessive heat, hot gases or flames under conditions of use.

Fire-retardant-treated (FRT) plywood

Plywood that has been impregnated under pressure with mineral salts; in the event of fire, the burning wood and salts emit noncombustible gases and water vapor instead of the usual flammable vapors.


Components used to weatherproof or seal roof system edges at perimeters, penetrations, walls, expansion joints, valleys, drains and other places where the roof covering is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing.

Gable (Includes illustration)

The vertical triangular portion of the end of a building having a double-sloping roof from the level of the eaves to the ridge of the roof.

Galvanized steel

Steel coated with zinc for corrosion resistance.


(1) A roof that has two pitches on each side of a central ridge where the upper roof areas have less slope than the lower roof areas; (2) a roof with two inclines on each slope.


A metal thickness measurement; a smaller gauge number indicates a thicker metal.

Glass felt

Glass fibers bonded into a sheet with resin and suitable for impregnation with asphalt in the manufacture of bituminous waterproofing, roof membranes and shingles.


Opaque, natural or synthetically colored aggregate commonly used to surface cap sheets, shingles and other granule-surfaced roof coverings; also referred to as mineral or ceramic granules.

Gravel stop

A flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing.


A channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.

Gypsum board panels

Cementitious board stock with noncombustible core primarily comprised of gypsum that is commonly used as a barrier board, thermal barrier or cover board in a roof assembly.


A method of spot-applying asphalt-based adhesive to shingles for securement and wind resistance. Also termed "hand-sealing."

Hip (Includes illustration)

The sloping line along the outer angle formed by the meeting of two sloping sides of a roof with eaves that meet at a right angle.

Hip roof (Includes illustration)

A roof that rises by inclined planes from all four sides of a building to form hips at the intersection of adjacent roof slopes.

Ice dam (Includes illustration)

A mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the overhang of a steep roof causing ice and water to back up under roofing materials.


Any of a variety of materials designed to reduce the flow of heat from or into a building. See "thermal insulation."


A felt, metal or membrane sheet material used between courses of steep-slope roofing to improve the weather- and water-shedding characteristics of the primary roof covering during times of wind-driven precipitation; typically used with wood shakes.

Interlocking shingles

Individual shingles that mechanically attach to one another to provide enhanced wind resistance without reliance on sealing strips.


Any of the small timbers, metal or wood beams arranged parallel to one another and spanning from wall to wall to support a floor, ceiling or roof of a building.

Kick-out flashing (diverter)

A metal flashing detail installed at the eave end of a roof-to-wall transition designed to direct runoff away from the wall or wall cladding.

Laminated shingles

See "dimensional shingles."


That part of a roofing, waterproofing or flashing component that overlaps or covers any portion of the same or another type of adjacent component.


A soft, malleable, naturally weathering heavy metal; has low melting point and a high coefficient of thermal expansion.

Low-slope roofs

A category of roofs that generally includes weatherproof membrane types of roof systems installed on slopes at or less than 3:12.

Mansard (Includes illustration)

A decorative steep-sloped roof on the perimeter of a building.


Construction, usually set in mortar, of natural building stone or manufactured units, such as brick, concrete block, adobe, glass block, tile, manufactured stone or gypsum block.


A flexible or semiflexible roof covering or waterproofing whose primary function is to exclude water.

Metal flashing

See "flashing"; frequently used as through-wall-, step-, cap- or counterflashing.

Metal roof panel

A sheet-metal product having an installed weather exposure less than 3 square feet per sheet.


A superficial growth produced on organic matter or living plants by fungi.

Mineral-surfaced roofing

Roofing materials with a surface or top layer consisting of a granule-surfaced sheet.

Modified bitumen

See "polymer-modified bitumen."


A surface growth of fungus on damp or decaying matter. The term has no taxonomic significance and is used only in a general sense of visible fungal growth on organic matter. See "mildew."


A surface growth of fungus on damp or decaying matter. The term has no taxonomic significance and is used only in a general sense of visible fungal growth on organic matter. See "mildew."