Roofing Glossary of Terms

Commercial roofing terminology.

aggregate pavers: a surfacing or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock, or marble chips.

alligatoring: the cracking of the surfacing bitumen on a built-up roof that produces a pattern of cracks similar in appearance to an alligator’s hide.

aluminum: a non-rusting metal used in roofing for metal roofing and the fabrication of gutter and flashings.

Amalgamated™ Tapered Insulation System: a roofing system developed by Pinnacle Roofing Systems which uses multiple, increasing tapers that become steeper toward the edge of a flat roof in order to provide better insulation distribution, avoid ponding, and allow for more adequate drainage as roofs age.

asphalt: a bituminous waterproofing agent applied to roofing materials during manufacturing.

asphalt emulsion: a mixture of asphalt particles and an emulsifying agent such as bentonite clay and water.

ballast: a material installed over the top of a roof membrane to help hold it in place. Ballasts are loose laid and can consist of aggregate or concrete pavers.

batten: a strip of wood usually fastened to the structural deck for use in attaching a primary roof system such as tile; or a plastic strip, wood strip, or metal bar which is used to fasten or hold the roof and/or base flashing in place.

bitumen: any of various flammable mixtures of hydrocarbons and other substances, occurring naturally or obtained by distillation from coal or petroleum, that are a component of asphalt and tar and are used for surfacing roads and for waterproofing.

blocking: pieces of wood built into a roof assembly used to stiffen the deck around an opening, support a curb, or for use as a nailer for attachment of membranes or flashing.

boot: a piece of material preformed to protect roof penetrations from dirt, moisture, and other foreign and/or damaging substances.

built-up roof/BUR: a roof consisting of multiple layers of reinforcing membrane and waterproofing materials, such as asphalt and ply sheets.

cant strip: a continuous strip of material (triangular in cross-section) used as a transition piece between the roof deck and a vertical surface, normally with a 45 degree sloping surface; or a continuous strip of wood or fiber fitted into an angle formed at the intersection of a horizontal surface and a vertical surface.

cap flashing: material used to cover the top edge of base flashings or other flashings.

cap sheet: one to four plies of felt bonded and top coated with bitumen that is laid over an existing roof as a treatment for defective roofs.

contractor’s warranty: the written promise to the owner of the roof and roofing materials for workmanship involved in roofing or re-roofing a building.

curb: a raised member used to support skylights, HVAC units, exhaust fans, hatches, or other pieces of mechanical equipment above the level of the roof surface; or a raised roof perimeter that is relatively low in height.

deck: the surface installed over the supporting framing members to which the roofing is applied.

deterioration: having become disintegrated and impaired in quality, functioning, or condition.

drainage: the act, process, mode of, or device for draining.

drip edge: a non-corrosive, non-staining material or steel flashing bent at a 90 degree angle that is placed along the outer perimeter of steep sloped buildings; used along the eaves and rakes to allow water run-off to drip clear of underlying construction.

drippage: bitumen material that drips through roof deck joints, or over the edge of a roof deck.

eaves: the horizontal, lower edge of a sloped roof.

EPDM: Ethylene Propylene Diene Monomer; a thermoplastic rubber with high tear strength that can be cross-linked by both peroxides and sulfur.

evaluation: the careful appraisal of a roofing system to determine the condition and functionality of its various components and to recommend any necessary or potential need for repair or maintenance.

FM: an abbreviation of Factory Mutual Research Corporation; an insurance-industry, standards-setting laboratory.

fascia: vertical roof trim located along the perimeter of a building, usually below the roof level, for waterproofing or decoration.

flashing: components used to seal the roof system in places where the roof covering is interrupted or terminated – such as around pipes, curbs, walls, etc. – to help prevent moisture entry into the roof system or building.

flat roof: a non-peaked roof, typically used on industrial or apartment buildings, which appears flat but has a slightly tapered pitch.

HVAC: heating, ventilating, and air conditioning equipment.

inspection: the checking or testing of roof system and its components against established standards.

insulation: material used to maintain a desired temperature in a building by reducing the flow of heat into and out of the building.

maintenance: the periodic scheduled upkeep of a roofing system.

manufacturer’s warranty: the written promise to the owner of the roof and roofing materials for material-related problems.

membrane: the portion of the roofing system that serves as the waterproofing material.

new roof: an entirely new roofing system, usually placed on new construction.

parapet wall: the part of a perimeter wall that extends above the surface of the roof.

perimeter: the outer boundary of a roof or roofing system.

pipe boot: a prefabricated flashing piece used to flash around circular pipe penetrations.

pitch: the degree of slope or steepness of the roof.

polymer: any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule.

ponding: the accumulation of water at low-lying or sagging areas of a roof.

proposal: a document stating the terms and conditions of a proposed roofing project submitted to a prospective client for approval and signature following a visual inspection of the project site and condition, or new building plans and specifications.

R-value: the measure of a material’s resistance to heat flow. The higher a material’s R-value, the more it insulates.

rakes: the inclined edge of a sloped roof over a wall from the eave to the ridge.

repair: the fixing of leaks, deterioration, cracks, and other such problems on an existing roof system.

re-roof: the replacement of a roof or portion of a roof, or the placement of additional roofing materials over an existing structure.

roof deck: the component in building construction which forms a platform on which the remainder of the BUR components are placed.

roof system: the entity made up of multiple roof components assembled to provide waterproofing, weatherproofing, and insulating for a building, including the waterproof covering, roof insulation, vapor barrier, and roof deck.

sag: settling or drooping of base flashings that have not been properly secured to a surface, or due to aging and deterioration, often occurring toward the center of a roof away from the perimeter.

scuppers: an outlet in the wall of a building or a parapet wall for drainage of water from a flat roof.

slope: the angle of incline of a roof.

straight tapered system: a slightly tapered roof in which the pitched surface sheds water toward a building’s perimeter.

substrate: the surface that the roof is installed upon.

termination: the sealed edges of a roof membrane.

underlayment: a layer of material (often tar paper) which is laid down on a bare deck before shingles are installed to provide additional protection for the deck.

white roof: a reflective roof that is more effective than traditional black asphalt roofs in keeping solar heat out of buildings and increasing energy savings.