D

Dampproofing: The 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 absolutely no slope or pitch.

Dead-Level Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type I. This asphalt is for use in roofs which do not exceed a in 12 slope (2%).

Dead Loads: Non-moving rooftop loads, such as mechanical equipment, the roof system and the roof deck.

Deck: The structural component of the roof of a building which provides the substrate to which the roofing system is applied.

Decking: See "Deck"

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 or 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, moisture or other contaminants.

Dormer: A framed projection through the sloping plane of a roof.

Double Graveling: The process of installing one layer of gravel in a flood coat of hot bitumen, removing the excess gravel and then installing a second layer of gravel in another flood coat of hot bitumen.

Downspout: A conduit for carrying water from a gutter, scupper, drop outlet or other roof drainage component to ground level. Also known as a Rain Water Leader.

Drain: a device used to carry water off of a roof.

Drip Edge: A metal flashing bent at a 90 angle that is installed along the roof edge. It’s function is to help direct runoff water away from the building and to terminate and secure the edge of the roof membrane.

Dry Bulb Temperature: The temperature of air in degrees Fahrenheit measured by an ordinary thermometer.

Dry Film Thickness: The thickness in mils (thousandths of an inch), of a dried coating or mastic.

Dry-In: The process of installing the underlayment in a steep slope roof application.

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.

E

Eave: A roof edge that extends out past the exterior wall line.

Eaves-Trough: Another name for Gutter.

Edge Stripping: Roofing material used to seal perimeter edge metal and the roof membrane. Generally consists of two to four plies of roofing felt or membrane adhered in alternate applications of bitumen.

Eave Venting: The installation of vent material or components along a roof edge as part of a ventilation system.

Elastomer: A material which, after being stretched, will return to its original shape.

Elastomeric: Properties of a material that will permit it to return to its original shape after being stretched.

Elongation: The ability of a material to be stretched or lengthened.

Embedment: In roofing, to uniformly press one material into another, such as aggregate into bitumen, roofing felt into bitumen, or granules into a coating.

Emulsion: Fine particles suspended in a liquid solution.

End Lap: Generally refers to the point at which the end of one roll of roofing felt or membrane overlaps the end of the adjacent roll.

Envelope: A continuous seal for preventing bitumen from leaking down into or off a building. Is constructed by extending the base sheet or other non-porous ply of felt beyond the edge of the field plies. It is then turned back onto the top of the system and adhered.

EPDM: Ethylene Propylene Diene Monomer. A rubber membrane commonly utilized as a roof membrane in low-slope roof applications.

Epoxy: A type of synthetic, thermosetting resin that produces hard, durable chemical-resistant coatings and adhesives.

Equipment Screen: A nonstructural wall or screen constructed around rooftop equipment such as HVAC units, curbs, etc. to conceal the equipment from view.

Equiviscous Temperature (EVT): The temperature at which a bitumen attains the proper viscosity for use in built-up roofing. There is usually a twenty-five degree Fahrenheit (25 F) variance permitted above and below the recommended EVT. The EVT is measured in application equipment immediately prior to application using a standard thermometer or it can be measured immediately after application using a laser thermometer.

The following tables have SAMPLE EVT temperatures:

ASPHALT – ASTM D 312

Asphalt Type

Mop Application ( F)

Mechanical Spreader Application ( F)

Type I Dead Level

350 25

375 25

Type II Flat

400 25

425 25

Type III Steep

425 25

450 25

Type IV Special Steep

450 25

475 25

 

COAL TAR – ASTM D 450

Coal Tar Type

Mop Application ( F)

Mechanical Spreader Application ( F)

Type I Pitch

360 25

380 25

Type III Bitumen

375 25

400 25

 

Ethylene Propylene Diene Monomer (EPDM): A thermoplastic rubber with high tear strength that can be cross-linked by both peroxides and sulfur. Commonly used as a roof membrane.

EVT: Equiviscous Temperature

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.

Extrusion: The process of manufacturing and/or shaping a material by forcing it through a die.

Eyebrow: A small, shed dormer protruding from the main roof or located on the side of a building below the level of the main roof. Eyebrow dormers are generally barrel shaped, but turn up at each end, resembling the shape of an eyebrow.

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