A roof assembly configured with each component placed immediately on top of the preceding component; each component is in contact with the adjacent component. No space is provided for ventilation of the roof assembly. Also known as a “compact” roof assembly.
W
Wash Coat
A primer, typically provided on the back side of painted metal products to help protect the underlying metal from wear and corrosion.
Water Cure
A method of curing a material, such as concrete, by applying a fine mist of water over the surface to control the rate of moisture evaporation from the material.
Water Stop
A diaphragm used across a joint as a sealant, usually to prevent the passage of water.
Water Table
The level within the ground, below which the soil is saturated with water.
Water Vapor Transmission
A measure of the rate of transmission of water vapor through a material under controlled laboratory conditions of temperature and humidity. Customary units are grains/h·ft2.
Water-Shedding
The ability of individual, overlapping components to resist the passage of water without hydrostatic pressure.
Waterproof
The quality of a membrane, membrane material, or other component to prevent water entry.
Waterproofing
Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.
Wear Course
The top layer of surfacing that carries pedestrian or vehicular traffic. Sometimes referred to as wearing surface.
Weather Damage
All roofing materials deteriorate from exposure to the weather at rates determined largely by the kind of material and the conditions of exposure. In general, inorganic roofing materials tend to deteriorate less rapidly from exposure than organic roofing materials. All types of roofing materials may be damaged by hail. Exposure to air pollutants and industrial or salt-laden atmospheres may accelerate the deterioration process of some roofing materials.
Weatherproof
The ability of a membrane or roof covering to prevent the passage of water with a limited amount of hydrostatic pressure.
Weep Holes
Small openings whose purpose is to permit drainage of water that accumulates inside a building component (e.g., a brick wall, skylight frame, etc.).
Weld
To join pieces of metal together by heat fusion.
Wet
A condition where free water is present in a substance.
Wet Bulb Temperature
The temperature of air as registered by a thermometer whose bulb is covered by a water wetted wick.
Wet Film Thickness
The thickness, expressed in mils, of a coating or mastic as applied but not cured. For comparison, see Dry film thickness.
Wicking
The process of moisture movement by capillary action.
Wind Clip
A steep-slope roofing attachment device that fits over the butt end of tile, slate and stone to help secure individual roofing units from wind uplift.
Wind Damage
Roofing materials are subject to damage from strong winds and flying debris. Generally, roofs are not designed to withstand winds of hurricane and tornado intensity. However, roofs may also be damaged by winds of moderate intensity, with gust that may reach 50 to 75 miles per hour. The primary cause of wind damage is from the partial vacuum created by wind blowing over the edge of the roof. Nature tries to neutralize the low-pressure area by bringing in air from a higher pressure area, usually from inside the building. This air pushes up on the bottom side of the roof assembly and, over time, loosens fasteners and breaks the adhesion making the roof susceptible to damage from the next moderate or strong wind. To counteract the effects of wind-uplift forces, the roofing and insulation should be adequately fastened to the roof deck, and a securely-fastened perimeter detail should be provided.
Wind Load
Force exerted by the wind on a structure or part of a structure.
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.
Wire Tie System
A system of attachment for steep-slope roofing units (e.g., tile, slate and stone) using fasteners (nails and/or screws) in conjunction with wire to provide a concealed fastening system.
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.
WSRCA
Western States Roofing Contractors Association
Wythe
A masonry wall, one masonry unit, a minimum of two inches thick.