Roofing Terms You Should Know

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

Drip edge: An L-shaped strip (usually metal) installed along roof edges to allow water run off 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 a cornice’s outer edge.

Felt/underlayment: A sheet of asphalt-saturated material (often called tar paper) used as a secondary layer of protection for the roof deck.

Fire rating: System for classifying the fire resistance of various materials. Roofing materials are rated Class A, B or C, with Class A materials having the highest resistance to fire originating outside the structure.

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

Gable: The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof

Gutter: The trough that channels water from the eaves to the downspouts

Hip: The inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.

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

Oriented strand board (OSB): Roof deck panels (4 by 8 feet) made of narrow bits of wood, installed lengthwise and crosswise in layers, and held together with a resin glue. OSB often is used as a substitute for plywood sheets.

Penetrations: Vents, pipes, stacks, chimneys-anything that penetrates a roof deck.

Rafters: The supporting framing to which a 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 rafters to cover a house or building.

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 of horizontal distance.

Soffit: The finished underside of the eaves

Square: The common measurement for roof area. One square is 100 square feet (10 by 10 feet).

Truss: Engineered components that supplement rafters in many newer homes and buildings. Trusses are designed for specific applications and cannot be cut or altered.

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

Vent: Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck

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