Roofing Terms

Algae discoloration: A type of roof discoloration caused by algae, also called fungus growth.

Attic: The open area above the ceiling and under the roof deck of a steep-sloped roof.

Asphalt shingle: a shingle manufactured by coating a reinforcing material (felt or fibrous
glass mat) with asphalt and having mineral granules on the side exposed to the weather.

Blisters: Bubbles that may appear on the surface of asphalt roofing after installation.

Bundle: A package of shingles. There are 3, 4 or 5 bundles per square.

Caulk: To fill a joint with mastic or asphalt cement to prevent leaks.

Chalk line: A line made on the roof by snapping a taut string or cord dusted with chalk. Used
for alignment purposes.

Closed cut valley: A method of valley treatment in which shingles from one side of the valley
extend across the valley while shingles from the other side are trimmed two inches from the
valley centerline. The valley flashing is not exposed.

Coating: A layer of viscous asphalt applied to the base material into which granules or other
surfacing is embedded.

Collar: Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe
opening. The collar is also called a vent sleeve.

Condensation: The change of water from vapor to liquid when warm, moisture-laden air
comes in contact with a cold surface.

Counter flashing: That portion of the flashing attached to a vertical surface to prevent water
from migrating behind the base flashing.

Course: A row of shingles or roll roofing running the length of the roof.

Cricket: A peaked saddle construction at the back of a chimney to prevent accumulation of
snow and ice and to deflect water around the chimney.

Deck or Decking: The structural “skin” of a roof over which roofing in applied. Most new
homes have decking made of plywood. There are three main types of decking commonly used
on residential roofing projects:

Plywood: Plywood is strong and durable. Use only exterior grade plywood for decking.
The thickness of plywood depends on the spacing of the rafters.

OSB: Oriented strand board (OSB) is cheaper than plywood, but not as strong as
plywood, and does not hold nails as well as plywood.

Tongue and groove 2-by-6: If a roof will be seen from the inside (no ceiling installed),
tongue and groove is used. It is a wood decking that provides great insulation without
additional rigid roof insulation in moderate climates.

Dimensional shingle: a shingle that is textured, overlayed, or laminated and designed to
produce a three-dimensional effect. Similar to Laminated shingle and Architectural shingle.

Dormer: A framed window unit that projects through the sloping plane of a roof.

Drip edge: A non-corrosive, non-staining material used along the eaves and rakes to allow
water run-off to drip clear of underlying construction.

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

Felt: A flexible sheet that is saturated with asphalt and used as an underlayment, sometimes
called “tar paper”

Flashing: Pieces of metal or roll roofing used to prevent seepage of water into a building
around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls,
dormers and valleys.

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

Granules: Ceramic-coated colored crushed rock that is applied to the exposed surface of
asphalt roofing products.

Hip: The inclined external angle formed by the intersection of two sloping roof planes. The hip
runs from the ridge to the eaves.

Intake Ventilation: The part of a ventilation system used to draw fresh air in. Usually vents
installed in the soffit or along the eaves of a building.

Joists: Any of the small timbers or metal beams ranged parallel from wall to wall in a
structure to support a floor or ceiling.

Mansard roof: A type of roof containing two sloping planes of different pitch on each of four
sides. The lower plane has a much steeper pitch than the upper, often approaching vertical.
Contains no gables.

Modified Bitumen: Roofing asphalt that has been blended with some of a broad range of
materials which improve its performance characteristics.

Open valley: Method of valley construction in which shingles on both sides of the valley are
trimmed along a chalk line snapped on each side of the valley. Shingles do not extend across
the valley. Valley flashing is exposed.

Pitch: Also known as “slope”, pitch is the measure of how “steep” a roof is. For example, if a
roof is “4 in 12”, the roof rises 4 inches for every horizontal run of 12 inches. The pitch of the
roof is a big factor in determining the kinds of materials that can be used and the longevity
of the roof. Usually, a steeper roof (higher pitch) will last longer due to its better drainage

Ply: The number of layers of roofing: i.e. one-ply, two-ply.

Racking: Roofing application method in which shingle courses are applied vertically up the
roof rather than across and up. Not a recommended procedure.

Rake: The inclined edge of a sloped roof over a wall from the eave to the ridge.

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

Shed roof: A roof containing only one sloping plane. Has no hips, ridges, valleys or gables.

Square: A unit of roof measure covering 100 square feet.

Starter strip: Asphalt roofing applied at the eaves that provides protection by filling in the
spaces under the cutouts and joints of the first course of shingles.

Step flashing: Flashing application method used where a vertical surface meets a sloping roof plane.

Tab: The exposed portion of strip shingles defined by cutouts.

Tear off: Removing an existing roof system.

Underlayment: A layer of asphalt saturated (sometimes referred to as tar paper) which is
laid down on a bare deck before shingles are installed to provide additional protection for the

Valley: The internal angle formed by the intersection of two sloping roof planes to provide
water runoff.

Woven Valley: Method of valley construction in which shingles from both sides of the valley
extend across the valley and are woven together by overlapping alternate courses as they are
applied. The valley flashing is not exposed. (Not Recommended)

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