Roof Terms Defined
Roof terms defined A - B
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Aggregate: A surfacing material or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock or marble chips.

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

Alligatoring: Alligatoring is term used to describe the cracking of surfacing bitumen on a built-up roof. These cracks are the result of the limited tolerance of asphalt to thermal expansion or contraction, and produce a pattern that resembles an alligator's hide.

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

Back surfacing: Fine mineral matter applied to the back side of shingles to keep them from sticking.

zBase flashing: That portion of the flashing attached to or resting on the deck to direct the flow of water onto the roof covering.

Battens: 1"x2"x4' wood strips nailed to the roof, upon which the field tile hangs.

Bird stop: In addition to preventing birds from nesting in the hollows of the tile, this length of formed metal or foam elevates the first course of tile so that it is positioned at the same angle as subsequent courses.

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

Built-up roof: An outer covering of a comparatively flat roof, consisting of several layers of saturated felt. As laid, each layer is mopped with hot tar or asphalt. The top layer is finished with a mineral or rock covering and a special coating.

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

Butt edge: The lower edge of the shingle tabs.

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.

Class "A": The highest fire-resistance rating for roofing as per ASTM E-108. Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.

Class "B": Fire-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating from sources outside the building.

Class "C": Fire-resistance rating that indicates roofing materials are able to withstand light exposure to fire originating from sources outside the building.

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.

Color-through: During manufacturing, the color is mixed throughout the roofing material to become an integral part of it. When the product is cut, the affected area shows the same color as the surface.

Concealed nail method: Application of roll roofing in which all nails are driven into the underlying course of roofing and covered by a cemented, overlapping course. Nails are not exposed to the weather.

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.

Coverage: Amount of weather protection provided by the roofing material. Depends on number of layers of material between the exposed surface of the roofing and the deck; i.e., single coverage, double coverage, etc.

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 or Decking: The structural "skin" of a roof over which roofing in 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 cheaper than plywood, but not as strong as plywood, and does not hold nails as well as plywood. One side has a slip resistant coating and should be placed facing up.

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. Also, the boards can be painted or stained on the inside to match the interior.

Step sheathing: Step sheathing is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.

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

Double coverage: Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.

Downspout: A pipe for draining water from roof gutters. A downspout is also called a leader.

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.

Dutch lap method: Application of giant individual shingles with the long dimension parallel to the eaves. Shingles are applied to overlap adjacent shingles in each course as well as the course below.

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

Eaves flashing: Additional layer of roofing material applied at the eaves to help prevent damage from water back-up.

Edging strips: Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for re-roofing with asphalt shingles.

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) as it not intended for use by itself.

Exposed nail method: Application of roll roofing in which all nails are driven into the cemented, overlapping course of roofing. Nails are exposed to the weather.

Exposure: Portion of the shingle exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.

Fascia: Horizontal trim at the eaves that covers the rafter ends.

Feathering strips: Tapered wood filler strips placed along the butts of old wood shingles to create a level surface when re-roofing over existing wood shingle roofs. Feathering strips are also called horse feathers.

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

Fiber-cement: A roofing material that has cellulose (wood fiber) mixed into it. Cellulose absorbs water and can add greatly to the roof's weight, while reducing its longevity.

Fiberglass mat: An asphalt roofing base material manufactured from glass fibers.

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 minimum 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 to 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 lays on the roof, and the other against the vertical wall of the dormer or chimney. · Flashing is one of the most important elements of the roof because it seals the seams and joints of the roof--the locations where leaks are most likely to occur. Often, flashing is not maintained well, or installed correctly in the first place. Check for the following signs that your flashing needs maintenance or repair: Rusting of metal flashing Excess leaves and debris in valleys or seams of the roof (can lead to rusting and corroding of the metal) Prolonged exposure to the elements such as moisture, UV rays, climate changes--especially when asphalt compounds or caulking material is used. Look for cracks, loss of elasticity and delamination. In many cases the flashing can be cleaned and then repaired, relaminated or repainted (even in the case of rust). In other cases, the flashing may need to be replaced.

Flashing cement: An asphalt-based cement used to bond roofing materials. Flashing cement is also known as mastic.

Free-tab shingles: Shingles that do not contain factory-applied strips or spots of self-sealing adhesive.

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 roof: 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.

HEX shingles: Shingles that have the appearance of a hexagon after installation.

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 four sides. A hip roof contains no gables.

Hip shingles: Shingles used to cover the inclined external angle formed by the intersection of two sloping roof planes.

Ice dam: Ice dams occur when snow melts near the ridgelines of warm roofs (roofs without adequate ventilation). As the water runs down the roof to the overhang, it cools and freezes. If the snow continues this melt and freeze process, an ice dam can form that can seep under the shingles, through the decking and into the house. This, of course, can cause serious roof leaks--even in freezing temperatures. The best prevention to ice dams is a well-ventilated (cool) roof. Additional protection for your roof can be applied with an impermeable ice and water membrane. The membrane is installed on top of the decking, under the roofing material. Temporary prevention of ice dams can also be done through the use of electric cables along the eaves of the roof (where the dams usually form). However, new ice dams can form above the cables and still cause extensive damage. Another emergency solution to ice dams is to fill a sock or nylon with calcium chloride. Lay the stocking vertically across the ice dam. The calcium chloride will melt the ice and release the water so that it can drain outside, and not inside your roof.

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.

Interlocking shingles: Individual shingles that mechanically fasten to each other to provide wind resistance.

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

Laminated shingles: Strip shingles containing more than one layer of tabs to create extra thickness. Laminated shingles are also called three-dimensional shingles.

Lap: To cover the surface of one shingle or roll with another.

Lap cement: An asphalt-based cement used to adhere overlapping plies of roll roofing.

Lean-to roof: A roof with one slope only that is built against a higher wall.

Life-cycle cost: The total lifetime cost of a roof. Calculated by adding maintenance costs to the installed price, then deducting the added value the roof provides when the home is resold.

Low slope application: Method of installing asphalt shingles on roof slopes between two and four inches per foot.

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.

Mastic: An asphalt-based cement used to bond roofing materials. Also known as flashing cement.

Metal drip edge: A narrow strip of non-corrodible metal used at the rake and eave to facilitate water runoff.

Mineral-surfaced roofing: Asphalt shingles and roll roofing that are covered with granules.

Nesting: A method of re-roofing with new asphalt shingles over old shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle tab.

New construction: Installing a roof system on new construction.

No-cutout shingles: Shingles consisting of a single, solid tab with no cutouts.

Non-prorated warranty: A warranty which provides full replacement costs for the item(s) covered during the full term of the warranty. In contrast, a prorated warranty merely reimburses a percentage of replacement costs, depending on the age of the roof.

Non-veneer panel: Any wood based panel that does not contain veneer and carries an APA span rating, such as wafer board or oriented strand board.

Normal slope application: Method of installing asphalt shingles on roof slopes between 4 inches and 21 inches per foot.

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.

Organic felt: An asphalt roofing base material manufactured from cellulose fibers.

Organic shingle: An asphalt shingle reinforced with organic material manufactured from cellulose fibers.

Overhang: That portion of the roof structure that extends beyond the exterior walls of a building.

Pallets: Wooden platforms used for storing and shipping bundles of shingles.

Parapet: A low protective wall that extends above the roofline or balcony for support.

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 capabilities.

Plastic cement: A compound used to seal flashings and in some cases to seal down shingles as well as for other small waterproofing jobs. Where plastic cement is required for sealing down shingles, use a dab about the size of a half dollar unless otherwise specified.

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.

Rafter: The supporting framing member 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.

Random-tab shingles: Shingles on which tabs vary in size and exposure.

Release tape: A plastic or paper strip that is applied to the back of self-sealing shingles. This strip prevents the shingles from sticking together in the bundles, and need not be removed for application.

Re-cover (overlay): The installation of a new roof system over an existing system without removing an existing system.

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 shingles: Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.

Rise: The vertical distance from the eaves line to the ridge.

Roll roofing: Asphalt roofing products manufactured in roll form.

Roofing tape: An asphalt-saturated tape used with asphalt cements for flashing and patching asphalt roofing.

Run: The horizontal distance from the eaves to a point directly under the ridge. One half the span.

Saturant: Asphalt used to impregnate an organic felt base material.

Self-sealing shingles: Shingles containing factory-applied strips or spots a thermal sealing tab cement to firmly cement the shingles together automatically after they have been applied properly and exposed to warm sun temperatures. In warm seasons, the seal will be complete in a matter of days. In colder seasons, sealing time depends on the temperature and amount of direct sunlight hitting the shingles. Hand sealing with plastic cement should be done to ensure sealing in winter.

Self-sealing strip or spot: Factory-applied adhesive that bonds shingle courses together when exposed to the heat of the sun after application. Also known as self-sealing cement.

Selvage: That portion of roll roofing overlapped by the succeeding course to obtain double coverage.

Shading: Slight differences in shingle color that may occur as a result of normal manufacturing operations.

Sheathing: Exterior grade boards used as a roof deck material. "Step sheathing" is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.

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

Single coverage: Asphalt roofing that provides one layer of roofing material over the deck.

Slope: The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.

Smooth-surfaced roofing: Roll roofing that is covered with ground talc or mica instead of granules (coated).

Soffit: The finished underside of the eaves.

Soil stack: A vent pipe that penetrates the roof.

Span: The horizontal distance from eaves to eaves.

Specialty eaves flashing membrane: A self-adhering, waterproofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain.

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

Square-tab shingles: Shingles on which tabs are all the same size and exposure.

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.

Steep slope application: Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.

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

Strip shingles: Asphalt shingles that are approximately three times as long as they are wide.

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

Tar paper: See "Felt" Tear off: Removing an existing roof system.

Telegraphing: A shingle distortion that may arise when a new roof is applied over an uneven surface.

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.

Top lap: That portion of the roofing covered by the succeeding course after installation.

UL: Underwriters Laboratories, Inc.

UL label: Label displayed on packaging to indicate the level of fire and/or wind resistance of asphalt roofing.

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 deck.

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

Vent: Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck

Vent sleeve: See collar. 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.