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This glossary was designed to help those not directly involved in roofing with their understanding of roofing terminology. Many technical and chemical terms were not included.

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

Eaves-Trough: Another name for Gutter.

ECH: Polyepichlorohydrin. See also Epichlorohydrin.

Edge Stripping: Roofing material used to seal perimeter edge metal and the roof itself.

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.

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.

Elastomeric Coating: A coating that can be stretched to twice its dimensions and that will return to original when tension is released.

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. See also Asphalt Emulsion and Bituminous Emulsion.

End Lap: The extension of one component of material past the end of an adjacent piece of material.

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. See also Bitumen-Stop.

EPDM: Ethylene Propylene Diene Monomer.

Epichlorohydrin (ECH): A synthetic rubber material similar to EPDM with a stronger resistance to animal fats and oils than EPDM.

Epoxy: A type of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.

Equipment Screen: A nonstructural wall or screen constructed around rooftop equipment such as HVAC units, curbs, etc. to hide the look of the equipment and make the structure more aesthetically pleasing.

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 just prior to application using a standard thermometer or it can be measured just after application using a laser thermometer.

The following tables have SAMPLE EVT temperatures.


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 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.

EVT: Equiviscous Temperature

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.

Exposed-Nail Method: A method of installing roll roofing materials to 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.

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

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.


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