FYI

Words You Should Know

Deck/sheathing - The surface-usually plywood or oriented-strand board (OSB)-to which roofing materials are applied.

Dormer - A small structure projecting from a sloped roof, usually with a window.

Drip Edge - An L-shaped strip (usually metal) installed along the edges of the roof to allow water runoff to drip clear of the deck, eaves, and siding.

Eave - The horizontal lower edge of a sloped roof.

Fascia - A flat board, band, or face located at the outer edge of the cornice.

Felt/Underlayment - A sheet of asphalt-saturated material used as a secondary layer of protection for the roof deck.

Fire Rating - UL system for classifying the fire resistance of various materials. Roofing materials are rated "Class A," "B," or "C," with "A" materials having the highest resistance to fire originating outside the structure.

Flashing - Sheet metal used to prevent the seepage of water around any intersection or projection in a roof, such as vent pipes, chimneys, valleys, and the joints at vertical walls.

Louvers - Slatted devices installed in the gable or soffit (the underside of the eaves) to ventilate the space below the roof deck and equalize air temperature and moisture.

Oriented-strand board (OSB) - Roof deck panels (4 feet x 8 feet) made of narrow bits of wood, laid down lengthwise and crosswise in layers, held together with a resin "glue." Often used as a substitute for plywood sheets.

Penetrations - Vents, pipes, stacks, chimneys - anything that sticks up through the roof deck.

Rafter - The supporting framing to which the roof deck is attached.

Rake - The inclined edge of a roof over a wall.

Ridge - The top edge of two intersecting, sloping roof surfaces.

Sheathing - The boards or sheet materials that are fastened to the roof's rafters to cover the house.

Slope - Measured by rise in inches for each 12 inches of horizontal run: A roof with a 4-in-12 slope rises 4 inches for every foot.

Square - The common measurement for roof area is 100 square feet (10 feet x 10 feet).

Truss - The engineered components that have supplemented rafters in many newer houses. They are designed for specific applications and cannot be cut or altered in any way.

Valley - The angle formed at the intersection of two sloping roof surfaces.

Vapor Retarder - A material designed to restrict the passage of water vapor through a roof system or wall.