Dampproofing: Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.
Dead Level: A roof with no slope or pitch.
Dead-Level Asphalt: Asphalt for use in roofs which do not exceed a ¼ in 12 slope (2%).
Dead Loads: Permanent, non-moving loads on a roof resulting from the weight of a building’s components, equipment, and the roof system itself.
Deck: The structural component of the roof of a building which provides the substrate to which the roofing system is applied.
Deflection: The downward displacement of a structural member under load.
Delamination: Separation of laminated layers of a material or system.
Dimensional Shingle: A shingle that is textured or laminated to produce a three-dimensional effect. Also known as Laminated and Architectural Shingles.
Dimensional Stability: The ability of a material to retain its current properties and to resist a change in size resulting from exposure to temperature changes and moisture.
Dome: A roof with a partial-spherical shape.
Dormer: A framed projection through the sloping plane of a roof.
Downspout: A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level.
Drain: A plumbing fixture designed to remove water from a roof by gravity.
Drip Edge: A steel flashing bent at a 90º angle that is placed along the outer perimeter of steep sloped buildings and used to help direct runoff water away from the building. Drip Edge resembles nosing, except that it has an outwardly-angled bottom edge.
Dry Rot: Wood rot caused by certain fungi. Dry rot can result from condensation build-up, roof leaks that go untended, or from other problems. Dry rot will not remain localized. It can spread and damage any lumber touching the affected area.
Eave: A roof edge that extends out past the exterior wall line.
Edge Stripping: Roofing material used to seal perimeter edge metal and the roof itself.
Elastomeric: A material that will return to its original shape after being stretched.
Elastomeric Coating: A coating with elastomeric properties.
Emulsion: Fine particles suspended in a liquid solution.
End Lap: The extension of one component of material past the end of an adjacent piece of material.
Equipment Screen: A nonstructural wall or screen constructed around rooftop equipment such as HVAC units, curbs, etc. to hide the equipment from view and make the structure more aesthetically pleasing.
Equiviscious Temperature (EVT): The temperature at which bitumen attains the proper viscosity for use in built-up roofing. The EVT is usually expressed as a range, with a twenty-five degree Fahrenheit (25° F) variance permitted above and below the recommended EVT.
Expansion Joint: A built-in separation between building sections to allow for free movement between the sections without damaging the building’s structural components.
Exposed-Nail Method: A method of installing roll roofing materials where all nails/fasteners are visible and exposed to the elements.
Exposure: The portion of the membrane that is not overlapped by the succeeding ply or course. Or, the portion of the roofing material exposed to the weather after being installed.
Fallback: A reduction in the softening point temperature of asphalt that occurs when asphalt is overheated for prolonged periods of time.
Fascia: Vertical roof trim located along the perimeter of a building, usually below the roof level. Its use can be either decorative or for waterproofing.
Felt: A roofing sheet made of interwoven fibers.
Felt Machine: A machine used to install built-up roofing by dispensing bitumen and felt at the same time.
Fiberglass Insulation: Rigid boards or blankets composed of glass fibers that are used to insulate roofs and walls.
Field of the Roof: The central part of a roof, away from the perimeter.
Fishmouth: An opening along the exposed edge of an installed ply of felt caused by shifting of the ply during installation.
Flash: To install flashing components.
Flash Point: The lowest temperature of a liquid material at which combustion will occur when air reaches its surface.
Flashing: Components used to seal the roof system at areas where the roof covering is interrupted or terminated. For example, pipes, curbs, walls, etc. all have special components that, when correctly installed, will help prevent moisture entry into the roof system or building.
Flood Coat: The surfacing layer of bitumen into which aggregate is embedded on an aggregate-surfaced built-up roof.
Gable: A triangular-shaped portion of the endwall of a building located directly under the sloping roof and above the eave line.
Galvanized Steel: Steel that is coated with zinc to aid in corrosion resistance.
Gambrel: A roof that has two different pitches.
Glaze Coat: The uppermost layer of asphalt on a smooth-surfaced built-up roof membrane.
Granule: A small aggregate, naturally or synthetically colored, that is used to surface cap sheets, shingles, and other granule-surfaced roof coverings.
Gravel: Aggregate consisting of rock fragments or pebbles.
Gravel Stop: A flanged, sheet metal edge flashing with an upward projection installed along the perimeter of a roof to prevent loose aggregate from falling over the roof edge to the ground or level below.
Green Roof System: A system of plantings and/or landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components, such as a protection course, a root barrier, a drainage layer, thermal insulation and an aeration layer, and an overburden of growth medium and plantings.
Gutter: A channel, usually made of sheet metal, that is installed along the downslope perimeter of a roof to convey water from the roof to the drain leaders or downspouts.
Half Gable Roof: See Shed Roof.
Headlap: The distance that the topmost ply of roofing felt overlaps the undermost ply or course.
Heat Welding: Fusing the seams of separate sections of roofing material together through the use of hot air or an open flame and pressure.
Hip: The angle formed by the intersection of two sloping roof planes.
Hip Roof: A roof that rises by inclined planes on all sides of a building. The line where two adjacent sloping sides of a roof meet is called the hip.
Hoist: A mechanical lifting device. A hoist can be hand or electrically operated.
Holiday: An area where a liquid-applied material is missing.
Hot: Slang for hot bitumen.
HVAC: Acronym for Heating, Ventilating, and Air Conditioning.
Impact Resistance: A roof assembly’s ability to withstand damage due to falling objects, such as hail.
Infrared Thermography: The use of an infrared camera to detect moisture in a roof system.
Insulation: Material used to increase the energy efficiency of a building by reducing the flow of heat to and from that building. See also Thermal Insulation.
Interlayment: A material that is usually installed between adjacent rows of wood shakes to enhance the roof’s ability to prevent water intrusion.
Interlocking Shingles: Shingles that lock together to provide better wind resistance.
Inverted Roof Membrane Assembly (IRMA): A roof assembly in which the insulation and ballast are placed on top of the roof membrane, rather than beneath it. Also known as a Protected Membrane Roof.
Jack: See Roof Jack.
Joint Tape: Tape used to seal joints between insulation boards.
Joist: Any of the parallel horizontal beams set from wall to wall to support the boards of a floor, ceiling or roof of a building.
Knee Cap: Sheet metal trim that fits over a panel rib after it has been cut and bent.
Laminated Shingles: See Dimensional Shingles or Architectural Shingles.
Lap: The part of the roofing material that overlaps a section of adjacent material.
Lead: A common metal used for flashing material.
Live Loads: Temporary items on a roof such as people, snow, etc. which the roof must be designed to support.
Loose-Laid Roof Membranes: Roofing material that is only attached at the perimeter and at penetrations and held in place by ballast, pavers, or other materials.
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