Delamination. Separation of felt plies in a built-up membrane or
separation of previously factory-laminated insulation boards.
Dew Point. Temperature at which condensation of water vapor in a
space begins for a given state of humidity and pressure as the
vapor temperature is reduced; the temperature corresponding to
saturation (100% relative humidity) for a given absolute
humidity at constant pressure.
DFT. Dry film thickness, used as a measure of liquid-applied
Double pour. A doubling of the flood-coat, graveling-in
operation, to provide additional waterproofing integrity to the
membrane (done once, loose aggregate removed and done again).
Edge stripping. Application of narrow felt strips to cover a
joint between flashing and built-up membrane.
Elastomer. A macromolecular material that rapidly regains its
original shape after release of a light deforming stress.
Elastomeric. Having elastic properties, capable of expanding or
contracting with the surfaces to which the material is applied
Emulsion. An intimate mixture of bitumen and water, with uniform
dispersion of the bitumen globules achieved through a chemical or
clay emulsifying agent.
Envelope. The continuous edge formed by folding an edge base
felt over the plies above, securing it to the top felt. The
envelope thus prevents bitumen seepage through the exposed edge
joints of the laminated, built-up roofing membrane.
Equilibrium moisture content. The moisture content of a material
at a given temperature and relative humidity, expressed as
percent moisture by weight.
Equiviscous temperature (EVT). The temperature at which bitumen
has the viscosity of 125 centistokes for hot mopping.
Ethylene propylene diene monomer (EPDM). A thermosetting,
synthetic rubber used in single-ply elastomeric sheet roof