Common Roofing Terminology

Deck sheathing: A layer of boards or of other wood or fiber materials applied to the outer studs, joists, and rafters of a building to strengthen the structure and serve as a base for an exterior weatherproof cladding. (source)

Dormer: A window that projects vertically from a sloping roof.

Drip Edge: A metal flashing or other overhanging component with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components.

Eave: The part of a roof that meets or overhangs the walls of a building.

Fascia: A wooden board or other flat piece of material such as that covering the ends of rafters.

Underlayment: It forms a water and ice barrier in areas affected by extreme weather conditions. It may be described as an underlayment beneath another underlayment, because a synthetic or felt layer is applied over its top and before the application of shingles or tiles. (source)

Flashing: A thin, impervious sheet of material placed in construction to prevent water penetration or direct the flow of water. Flashing is used especially at roof hips and valleys, roof penetrations, joints between a roof and a vertical wall, and in masonry walls to direct the flow of water and moisture.

Louvers: Each of a set of angled slats or flat strips fixed or hung at regular intervals in a door, shutter, or screen to allow air or light to pass through.

Rafters: One of several internal beams extending from the eaves to the peak of a roof and constituting its framework.

Rake: The rake of a roof is the outer edge that runs from the eave to the ridge, or peak, of the roof. It is typically perpendicular to the eave. (source)

Ridge: The ridge of a sloped roof system is the horizontal top area where two sloped roof areas meet. (source)

Slope: Roof systems and materials generally are divided into generic classifications: low slope and steep slope. Low slope roofing includes water impermeable, or weatherproof, types of roof membranes installed on slopes less than or equal to 3:12 (14 degrees). Steep slope roofing includes watershedding types of roof coverings installed on slopes exceeding 3:12 (14 degrees). (source)

Square: One square is equal to 100 square feet. Examples where the unit is used are roofing shingles, metal roofing, vinyl siding, and fibercement siding products. Some home builders use squares as a unit in floor plans to customers.

Truss: A framework, typically consisting of rafters, posts, and struts, supporting a roof, bridge, or other structure.

Valley: A depression or angle formed by the meeting of two inclined sides of a roof. (source)

Vapor retarder: A vapor retarder helps control the amount of moisture passing through the insulation and collecting inside exterior walls, ceilings and floors. It is rated in perms (“permeance”). The lower the perm rating, the better the water vapor permeance. (source)