Definitions of common roofing terms

Cornice:  The overhang of the roof at the eaves line that forms a connection between the roof and the sidewalls.

Deck/sheathing:  The flat, substructure surface, usually plywood or oriented strand board (OSB – see definition below), 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) is installed along roof edges to allow water runoff to drip clear of the deck, eaves, and siding.

Eave:  The overhanging lower edge of a 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) is used as a secondary layer of protection for the roof deck. Its purpose is to waterproof roofs to prevent moisture from reaching past the top of 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 are used to prevent the seepage of water around any intersection or projection in a roof system, such as joints at vertical walls, chimneys, vent pipes, and valleys.

Louvers (vents):  Slatted devices installed in a gable or soffit to allow ventilation in the space below a roof deck and even out air temperature and moisture.

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

Penetrations:  Anything that penetrates a roof deck, such as vents, pipes, stacks, and chimneys.

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/Pitch:  Measured by rise in inches for every 12 inches of horizontal run: A roof with an 8-12 slope rises 8 inches for every foot of horizontal distance.

Soffit:  The underside area of the overhang of the roof.

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.

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

If you have any questions or would like us to add a specific definition, please contact us!