Glossary of Roofing Terms

Understanding Common Roof System Terminology Will Help You Plan for the Roofing Process

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.
Bundle: A package of shingles. There are 3, 4, or 5 bundles per square.
Caulk: Using mastic or asphalt cement to fill a joint to prevent leaks.
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.
Collar: Also called a vent sleeve, a collar is a pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening.
Condensation: The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.
Counter Flashing: The 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.
Cutout: The open portions of a strip shingle between the tabs.
Deck, Decking, or Sheathing: The structural “skin” of a roof over which roofing is applied. Most new homes have decking made of plywood. There are four main types of decking commonly used on residential roofing projects:
- Plywood: Plywood is strong, durable, and light. It comes in many grades with ratings from A to D. Use only exterior grade plywood for decking. The thickness of plywood depends on the spacing of the rafters.
- OSB (Oriented Strand Board): OSB is less expensive than plywood but not as strong and does not hold nails as well. One side has a slip-resistant coating and should be placed facing upward.
- Step Sheathing: Step sheathing is used alone or in combination with solid sheathing for the installation of tiles or shakes. Step sheathing allows air circulation under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move.
- Tongue and Groove 2-by-6: If a roof is 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. Also, the boards can be painted or stained on the inside to match the interior.
Dimensional Shingle: A shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect.
Dormer: A framed window unit that projects through the sloping plane of a roof.
Downspout: A pipe for draining water from roof gutters. A downspout is also called a leader.
Drip Edge: An L-shaped, non-corrosive, non-staining material (usually metal) used along the eaves and rakes to allow water run-off to drip clear of underlying construction.
Eave: The horizontal, lower edge of a sloped roof.
Edge Venting: The installation of a vent material along the roof edge (e.g., Starter Vent) as part of a ventilation system. Edge vent material should be used in conjunction with other venting material (e.g., ridge vent).
Exposure: The portion of the shingle is exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.
Fascia or Fascia Board: (pronounced fey-shuh) Horizontal trim at the eaves that covers the rafter ends.
Felt: A flexible sheet that is saturated with asphalt and used as an underlayment. Sometimes called “tar paper”, the GAF brand used is called Shingle Mate, made with a fiberglass mat instead of a paper mat.
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. Galvanized metal flashing should be a minimum of 26-gauge. There are 4 main types of flashing used in residential roofing systems:
- Valley Flashing: This flashing is used in open valleys of the roof. Most often leaks are found in the valley flashings due to flashing that is nailed too tightly to the decking or shingles that are not trimmed far enough off the flashing.
- Plumbing Vent Flashing: Plumbing vent flashing prevents rainwater from running into holes cut for pipes in the roof. This flashing is sold according to the size of the vent pipe and the roof angle. Roofing material is installed over the flashing.
- Lead Flashing: When working with tile roofs, lead flashing is used. In the case of a plumbing vent flashing, the lead flashing is actually molded to the shape of the tile’s surface. Then, the top of the lead flashing is covered by the next tile to prevent water from seeping under the flashing.
- Step Flashing: When a chimney or dormer wall intercepts the slope of the roof, step flashing is used. Step flashing is usually a metal piece that is bent in the middle, so that one end sits on the roof, and the other against the vertical wall of the dormer or chimney.
Gable: The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.
Gable Roof: A type of roof containing sloping planes of the same pitch on each side of the ridge. A gable roof typically contains a gable at each end.
Gambrel: A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. A gambrel roof usually contains a gable at each end, just like a standard gable roof.
Granules: Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.
Gutter: The trough that channels water from the eaves to the downspouts.
Hip: The inclined external angle formed by the intersection of two sloping roof planes. The hip runs from the ridge to the eaves.
Hip Roof: A type of roof containing sloping planes of the same pitch on each of the four sides. A hip roof contains no gables.
Laminated Shingles: Strip shingles containing more than one layer of tabs to create extra thickness. Laminated shingles are also called three-dimensional shingles.
Mansard Roof: A type of roof containing two sloping planes of different pitches on each of the four sides. The lower plane has a much steeper pitch than the upper, often approaching vertical. (has no gables)
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.
Overhang: That portion of the roof structure that extends beyond the exterior walls of a building.
Pitch: Also known as “slope”, the 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 capabilities.
Racking: Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. It is not a procedure we recommend.
Rafter: The supporting framing member is immediately beneath the deck, sloping from the ridge to the wall plate.
Rake: The inclined edge of a sloped roof over a wall from the eave to the ridge.
Re-roofing: Installing a new roof system on a building that is not new.
Ridge: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
Ridge Vent: Vent placed along the ridge of the roof. It allows ventilation of the roof by slightly raising the level of the ridge to leave room for air flow. A filtration fabric placed in the side vents allows air to move through while preventing insects from entering.
Rise: The vertical distance from the eaves line to the ridge.
Run: The horizontal distance from the eaves to a point directly under the ridge.
Sheathing: Exterior grade boards used as a roof deck material. “Step sheathing” is used alone or in combination with solid sheathing for the installation of tiles or shakes.
Shed Roof: A roof containing only one sloping plane. It doesn’t have hips, ridges, valleys or gables.
Slope: The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.
Soffit: The finished underside of the eaves.
Soil boot: A vent pipe that penetrates the roof.
Span: The horizontal distance from eaves to eaves.
Square: A unit of roof measure covering 100 square feet (10 feet by 10 feet).
Starter Strip: Asphalt roofing is applied at the eaves that protects by filling in the spaces under the cutouts and joints of the first course of shingles.
Steep Slope Application: Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.
Tab: The exposed portion of strip shingles is defined by cutouts.
Three-dimensional Shingles: See laminated shingles.
Three-Tab Shingle: The most popular type of asphalt shingle usually 12″ x 36″ in size with three tabs.
Underlayment: Roofing underlayment or roofing paper comes in three common types:
- Asphalt-Saturated Felt (Felt Paper)
- Rubberized Asphalt.
- Non-Bitumen Synthetics (Synthetic Felt Paper)
Valley: The internal angle formed by the intersection of two sloping roof planes to provide water runoff.
Vent: Any air outlet that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable, or soffit to ventilate the underside of the roof deck.
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.

Glossary of Roofing Terms

Understanding Common Roof System Terminology Will Help You Plan for the Roofing Process

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