Roofing Terminology
(Click on a letter to learn more)
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Edge Sheets
Felt strips that are cut to widths narrower that the standard width of the full felt roll. They are used to cover joints.
Edge Stripping
Application of felt strips cut to narrower widths than the normal width of the full felt roll.
Edge Venting
The practice of providing regularly spaced protected openings along a roof perimeter to relieve moisture vapor pressure.
Elastomer
A macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and the subsequent release of that stress.
Embedment
The process of pressing a felt, aggregate, fabric, mat, or panel uniformly and completely into hot bitumen or adhesive; the process of placing a material into another material so that it becomes an integral part of the whole material.
Emulsion
The intimate dispersion of an organic material and water achieved by using a chemical or clay emulsifying agent.
End Lap
The distance of overlap where one ply extends beyond the end of the immediately adjacent ply.
Envelope
A continuous felt fold formed by wrapping and securing a portion of a base felt back up and over the felt plies above it. The envelope is intended to prevent bitumen seepage from the edge of the membrane.
Epoxy
A class of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.
Equilibrium Moisture Content (EMC)
The moisture content of material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight; the typical moisture content of a material in any given geographical area.
Equiviscous Temperature (EVT)
The temperature at which bitumen attains the proper viscosity for built up membrane application.
Expansion Joint
A structural separation between two building elements designed to minimize the effect of the stresses and movements of a building's components and to prevent these stresses from splitting or ridging the roof membrane.
Exposure
The transverse dimension of a roofing element not overlapped by an adjacent element in any roof system. The exposure of any ply in a membrane may be computed by dividing the felt width minus two inches by the number of shingled plies; thus, the exposure of a 36-inch-wide felt in a shingled, four-ply membrane should be 8 1/2 inches; the time during which a portion of a roofing element is exposed to the weather.
Extrusion
A manufacturing process which consists of forcing batched and formulated material through an orifice.
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