Glossary of Roofing Terms

Chimney Cricket – A false roof behind a chimney used to divert water away from the chimney
Counter Flashing – The portion of the flashing attached to a vertical surface used to prevent water from migrating behind the base flashing
Deck/Sheathing – The surface, usually plywood or oriented strand board (OSB), 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) installed along the roof edges to allow water run-off to drip clear of the deck, eaves and siding
Eave – The roof area that projects past the walls
Fascia – A flat board, band, or face located on the outer edge of rake or eave
Felt/Underlayment – A sheet of asphalt- saturated material used as a secondary layer of protection; see also: Synthetic Underlayment
Fire Rating – System for classifying the fire resistance of various materials. In roofing, the materials are rated Class A, B or C. Class A materials have the highest resistance to fire originating outside the structure
Flashing – A thick, impervious sheet of material placed to prevent water penetration or to direct the flow of water away from the building
Gable – The portion at the end of a building that extends from the eaves to the peak
Metal Valley Flashing – The point at which two pitched roofs join (at an inside corner) is known as a valley and is where most shingle materials rely on a piece of metal for a watertight connection to each other
Oriented Strand Board (OSB) – Roof deck panels (usually 4’ x 8’) 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 – Vents, pipes, stacks, chimneys, and anything else 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 of two intersecting, sloping roof surfaces
Ridge Board – Horizontal board that serves as a support in the highest point of the roof structure
Ridge Vent – A type of vent installed at the peak of a sloped roof which allows warm, humid air to escape a building’s attic
Sheathing – The boards or sheet materials that are fastened to rafters 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 12 inches of horizontal distance
Soffit – The underside of the eave of a building
Square – The common measurement for roof area. One square is 100 square feet
Step Flashing – Galvanized steel or aluminum metal bent at 90 degrees woven between each row of shingles installed when a roof slope meets a vertical wall
Synthetic Underlayment – A sheet of material typically made from polypropylene, polyester, or fiberglass fabric which weighs less than felt paper and can be manufactured with an anti-slip surface, and can withstand exposure to the elements for six months that is used as a secondary layer of protection
Truss – Engineered components that supplement rafters in many newer homes and buildings. Trusses are designed for specific application and cannot be cut or altered
Valley – The angle formed at the intersection of two sloping roof surfaces