Glossary D - I

Glossary: D to I


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Dampproofing: Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.
Dead Level: Refers to a roof with no slope or pitch.
Dead Loads: Permanent, non-moving loads on a roof resulting from the weight of a building's components, equipment, and the roof system.
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.
Degradation: A decline in the appearance, structure, or properties, of a material or substance.
Delamination: Separation of laminated layers of a material or system.
Dew Point Temperature: The temperature at which water vapor turns to liquid in cooling air at the existing atmospheric pressure and vapor content.
Dimensional Shingle: A shingle that is textured, or laminated to produce a three-dimensional effect. Also known as Laminated and Architectural Shingles. Please be aware that there are also shingles being produced that can be classified as Dimensional but not as Laminated. These shingles are comprised of a single piece of material rather than two different materials laminated together.
Dome: A roof with a partial-spherical shape.
Dormer: A framed projection through the sloping plane of a roof.
Double Coverage: Installing roofing so that there is twice the materials used resulting in a double layer of roofing.
Downspout: A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level. Also known as a Leader Pipe.
Drainage: A roof system's design features, such as shape, slope and layout that affect its ability to shed water.
Drip Edge: A steel flashing bent at a 90 deg. angle that is placed along the outer perimeter of steep sloped buildings; used to help direct runoff water away from the building. Drip Edge resembles nosing except that it has an outwardly-angled bottom edge (preferably hemmed).
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.
Dynamic Load: Any moving load on a roof such as people and equipment. Wind can also be considered a Dynamic Load.

Eave: A roof edge that extends out past the exterior wall line.
Eaves-Trough: Another name for Gutter.
Edge Venting: The installation of vent material along a roof edge (e.g., Starter Vent) as part of a ventilation system. Edge vent material should be used in conjunction with other venting material (e.g., ridge vent) as it not intended for use by itself.
EPDM: A thermoplastic rubber with high tear strength that can be cross-linked by both peroxides and sulfur.
Exhaust Vent: A device used to vent air from the roof cavity with vents that are installed on or near the higher portions of the roof such as the ridge.
Expansion Cleat: A cleat designed to handle thermal movement of the metal roof panels.
Expansion Joint: A built-in separation between building sections to allow for free movement between the sections without damaging the buildings structural components.
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.
Eyebrow: A small, shed roof protruding from the main roof or located on the side of a building below the level of the main roof.

Factory Seam: A splice/seam made in the roofing material by the manufacturer. It is preferable during installation to cut these splices out of the membrane.
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. The fibers can be wood or vegetable for Organic Felts, glass fibers for fiberglass felts, polyester, or asbestos.
Ferrule: A metal sleeve used as a spacer to keep gutter from being beat up when secured to fascia with spikes.
Field of the Roof: Refers to the central part of a roof away from the perimeter.
Field Seam: A non-factory material seam made by joining overlapping seams together with adhesives, heat welders, or other means.
Fillet: A sealant material installed at horizontal and vertical planes to remove 90? angles.
Finial: A decorative ornament on top of a spire, peak, gable etc.
Fishmouth: An opening along the exposed edge of an installed ply of felt caused by shifting the ply during installation.
Flange: A projection edge of a roof component such as flashings, skylight frames, pre-manufactured curbs, etc. Usually refers to the part that sits on the roof surface.
Flash: To install flashing components.
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.
Flashing Cement: A trowelable mixture of solvent-based bitumen and mineral stabilizers.
Flashing Collar: A flashing component used to seal soil pipe vents, hot stacks or other roof penetrations.
Flat Lock: A type of interlocking two separate metal panels by folding one panel over on top itself and the folding the other down under itself and then hooking the panels together.
Fleece: Mats or felts used as a membrane backer and composed of fibers.
Flood Coat: The surfacing layer of bitumen into which aggregate is embedded on an aggregate-surfaced built-up roof. A flood coat is applied at an approximate rate of 45 to 60 pounds per square (100 square feet).
Fluid-Applied Elastomer: A liquid elastomeric material that cures to form a continuous waterproofing membrane.
Freeze Board: A board at the top of the house's siding, forming a corner with the soffit.

Gable: The triangular upper part of a wall closing the end of a ridged roof.
Gable Roof: A roof configuration that has gable ends.
Gable-On-Hip Roof: A roof configuration with hips coming up from the eave corners that terminate into a gable roof.
Galvalume: Trade name for a protective coating composed of aluminum zinc.
Galvanic Action: A reaction between different metals in the presence of an electrolyte.
Galvanized Steel: Steel that is coated with zinc to aid in corrosion resistance. Galvanized steel for use in roofing should be Hot-Dipped Galvanized with a G-90 coating.
Gambrel: A roof that has two different pitches.
Geodesic Dome: A geodesic dome uses a pattern of self-bracing triangles in a pattern that gives maximum structural advantage, thus theoretically using the least material possible.
Glass Felt: (1) In the manufacturing of roofing materials - a sheet comprised of bonded glass fibers prior to being saturated with bitumen; (2) short for asphalt or coal tar saturated fiberglass felt membrane.
Granule: A small aggregate, naturally or synthetically colored, used to surface cap sheets, shingles, and other granule-surfaced roof coverings.
Gutter: A channel (usually sheet metal) installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.

Headlap: The distance that the topmost ply of roofing felt or shingle 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. Also known as heat seaming.
Hem: The edge created by folding metal back on itself. Metal is hemmed for safety and strength reasons.
Hip: The angle formed by the intersection of two sloping roof planes.
Hook Ladder: A ladder with a bracket at the top which hooks over the ridge of the roof, allowing the ladder to lay flat on the roofing material.
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.
Hypalon: The trademark name for Chlorosulfonated Polyethylene (CSPE), which is a single-ply roofing material.

Ice Dam: Ice formed at the transition from a warm surface to a cold surface, such as along the overhang of a house. The build-up of ice is the result of ice or snow melting on the roof area over the warmer, living area of a building and then refreezing when it runs down and reaches the overhang.
Impact Resistance: A roof assembly?s ability to withstand the impact from falling objects such as hail.
Intake Ventilation: The part of a ventilation system used to draw fresh air in. Usually vents installed in the soffit or along the eaves of a building.
Interlocking Shingles: Shingles that lock together to provide wind resistance. See also T-Lock.


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