Roof Dictionary

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Elasticity: the property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion).

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

Elastomeric coating: a coating that is capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions.

Elongation: to ratio of the extension of a material to the length of the material prior to stretching.

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.

EPDM: Ethylene propylene diene monomer.

Ethylene propylene diene monomer (EPDM): a thermoplastic rubber with high tear strength that can be cross-linked by both peroxides and sulfur.

Expansion joint: a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

Exposure: (1) the traverse dimension of a roofing element or component not overlapped by an adjacent element or component in a roofing covering. For example, the exposure of any ply in a built-up roof membrane may be computed by dividing the felt width, minus 2 inches (51 mm), by the number of shingled plies; thus, the exposure of 36 inch (914 mm) wide felt in a shingled, four-ply membrane should be approximately 8 1/2 inches (216 mm); (2) the dimension of sidewall or roofing covering that is not covered or overlapped by the up slope course of component. The typical exposure for a standard-sized, three-tab shingle is 5 inches (127 mm), depending on manufacturer specifications.