Watt

Manually forcing insulation boards against previously installed boards to tighten the joints.

(1) The degree of penetration liquid water makes into the membrane; (2) The amount of water absorbed by a material after immersion for a prescribed period of time. May be expressed as a percentage of the original weight of the material.

(1) A detail designed to prevent lateral water movement into the insulation where the membrane terminates at the end of a day's work, or used to isolate sections of the roofing system. It is usually removed before the continuation of the work; (2) A material seal that is designed to prevent lateral water movement into the edge of a roof system where the membrane terminates at the end of a day's work or used to isolate sections of the roof system. Cutoffs are usually removed before the continuation of work. See CUTOFF.

The quality of a membrane, membrane material or other component to prevent water entry.

Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

A measure of the membrane's ability to allow water vapor to pass through.

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. (See ASTM Standard E 96.)

The ability of the membrane to resist weathering; i.e., degradation due to sun, rain, wind, etc.

The negative condition where rain or snow penetrate the roof. The condition is typically wind-driven.

(1) An indoor accelerated weathering machine using carbon arcs or other forms of intense light to simulate the outdoor weathering process due to sunlight, moisture may also be sprayed onto the samples; (2) An instrument used to subject material specimens to accelerated weathering conditions.

Small openings whose purpose is to permit drainage of water that accumulates inside a building component (e.g., a brick wall, skylight frame, etc.)

A condition where free water is present in a substance.

The process of moisture movement by capillary action, as contrasted to movement of water vapor.

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.

Force exerted by the wind on a structure or part of a structure.

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. This force is then transmitted to the roof surface. Uplift may also occur because of the introduction of air pressure underneath the membrane and roof edges, where it can cause the membrane to balloon and pull away from the deck.

Being in or facing the direction toward which the wind is blowing. The side exposed to the prevailing wind.

Pressure treated with insect and fungus repellant, i.e., wolmanized lumber.

(1) 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. The valley flashing is not exposed.

(1) An upward, "tenting" displacement of a roof membrane, frequently occurring over insulation joints, deck joints and base sheet edges; (2) Membrane defect characterized by upward displacement of the membrane, usually over insulation board joints. See RIDGING.

A masonry wall, one masonry unit, a minimum of 2" thick.