Roofing 101

Glossary of Roofing Terms

Roofing Square: 100 Square feet.

Pitch: Rise of roof per 12 feet.

Rake Roof: The inclined edge of a sloped roof over a wall.

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

Hip: A type of roofing containing sloping planes of the same pitch on each of 4 sides. Contains no gables.

Ridge: The uppermost, horizontal external angle formed by the intersection of 2 sloping roof planes.

Soffit: The finished underside of the eaves.

Eave: The horizontal, lower edge of a sloped roof.

Hip and Ridge Cap: Composite cap that covers this part of the roof.

Rake Cap: Composite caps that cover the rake of a roof.

Slope: The uppermost, horizontal external angle formed by the intersection of 2 sloping roof planes.

Take-off: A plan for a roof that estimates the materials needed and the costs associated with the materials. Typically a finished roof take off will determine how many roofing squares are required for the job.

Stack Effect: Attic air heated by contact with a hot roof on a warm day tends to rise. This is natural convection, which pulls cooler air from the soffit up towards the ridge. Natural convection, with a balanced system of soffit and vents at or near the ridge is the most effective means of venting the roof.

N.F.A. (Net Free Area): The net free area for any airflow pathway (airway) shall be the gross cross-sectional area less the area of any physical obstructions at the smallest or most critical cross sectional area in the airway. The net free area shall be determined for each airway in the installed device. Although related, airflow and net free area (NFA) are separate measures of attic ventilation performance. NFA is a static measurement; airflow is a dynamic measurement. NFA is a mathematical calculation independent of field conditions. This value remains constant.

Airflow: is a performance measure that varies based on the conditions to which the vent is exposed. Variable pressure differences across a roof (such as that produced by wind or stack effect) will induce different flow rates.

CFM (Cubic Feet per Minute): indicates a mechanical device usually electric or solar powered that will draw air out of the attic at a constant and consistent rate.