Water Stop: Material placed over a joint and used to prevent water entry.
Waterproof: Being resistant to moisture infiltration.
Waterproofing: The treatment of a surface or structure in order to prevent the passage of water under hydrostatic pressure.
Water Trough: The area in a valley where water runs. Usually referred to with open valley configurations.
Weather: To undergo degradation in quality and appearance which is caused by exposure to the sun, wind, rain, etc.
Weep Holes: Small holes used to permit moisture to drain that has gathered inside a building component.
Weld: To join multiple metal or PVC components together by heat fusion.
Wet Bulb Temperature: Air temperature in ° F as measured by a thermometer with a bulb covered by a damp wick.
Wet Film Thickness: The thickness of an uncured material such as a coating.
Wick: To convey liquid by capillary action.
Wind Clip: A clip that slips over the ends of tile, slate and other steep slope roofing materials in order to help prevent wind uplift damage.
Wind Load: The force that wind puts on structures.
Wind Uplift: (1) The upward displacement of a section of a roof system or component caused by movement of air from a location of higher air pressure, such as inside a building, to an area of lower air pressure, such as the surface of a roof during a windy day. Strong wind across the surface of a roof, especially at corners and along perimeters, creates low air pressure above the surface of the roof. Nature will automatically try to compensate for this by moving air from an area of higher pressure such as inside a building. If all penetrations and perimeters are not properly sealed, then "blow-off" can occur. (2) Displacement or blow-off of shingles or other roofing caused by the wind.
Windward: Facing into the wind.
Wire Tie: A system for attaching heavy steep slope roofing materials such as slate r tile by using wire fasteners in addition to or in place of nails.
Woven Valley: A valley construction whereby the valley has a woven look which is effected by overlapping alternate courses of shingles from both sides of the valley.