Flashing:
Pieces of metal used to prevent water seepage 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 a gable end wall or in a soffit (the underside of the eaves) to ventilate the space below the roof deck and equalize air temperature and moisture.

Rake:
An extension of the roof over a wall at the gable end.

Ridge:
The top edge of two intersecting sloping roof surfaces.

Slope:
Slope is 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 horizontal foot, for instance. The steeper the slope, the more difficult the repair and more costly the labor.

Square:
The most common measurement for roof surfaces, it equals 100 square feet (10”x10”).

Underlayment/Felt:
A sheet of asphalt-saturated material (often called “tar paper”) used as a secondary layer of protection for the roof deck. It is rolled out on top of the roof deck and sits under the roof covering.

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 or wall.