Term Description

The property of a material that allows it to endure or resist exposure to the weather.


An artificial weathering device that uses a light source for ultraviolet testing.


The ability of a membrane or roof covering to prevent the passage of water with a limited amount of hydrostatic pressure.


To join pieces of material together by heat fusion.


A condition in which free water is present in a substance.

Wet film gauge

A gauge for measuring the thickness of wet coating as applied to a flat smooth surface.

Wet film thickness

The thickness, expressed in mils, of a coating or mastic as applied but not cured. For comparison, see "dry film thickness."


The ability for a coating to flow to a thin film when coming in contact with a surface or another cured coating without displaying any visible anomalies, such as beading or improper film formation.


The process of moisture movement by capillary action.

Wind screen

In spray polyurethane foam (SPF) roofing, a device to keep the SPF from drifting or being blown away by the wind from the spray area.

Wind uplift

The force caused by the deflection of wind at roof edges, roof peaks or obstructions causing a drop in air pressure immediately above the roof surface.


(1) The direction from which the wind is blowing; (2) the side facing the wind. For comparison, see ‚"leeward.‚"

Woven valley

A method of valley construction in which shingles or roofing from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied.


In spray polyurethane foam roofing, the volume of foam per unit weight normally expressed as board feet per pound or board feet per 1,000 pounds.


A soft, self-healing metal that reacts with the environment to produce a soft blue-gray zinc carbonate patina that protects the underlying metal from corrosion. Zinc is commonly used as sacrificial (galvanized) coating for a base metal such as sheet steel and iron, in various metal alloys and in oxide form as a white pigment.