Glossary and Definitions

The following is a list of roofing industry-standard terms and definitions.

  • Asphalt: a bituminous waterproofing agent applied to roof materials during manufacturing
  • Asphalt roof cement: a mixture of solvent-based bitumen, mineral stabilizers, other fibers or fillers
  • Architectural shingle: a shingle that offers a dimensional appearance
  • Ballast: an anchoring material, such as precast concrete pavers, which allows gravity to hold single-ply roof membranes in place
  • Base sheet: a coated felt used as the first ply in some multi-ply built-up and modified bitumen roof membranes
  • Batten: a cap or cover in a metal roof set over, or covering the joint between, adjacent metal panels
  • Bitumen: any material composed principally of bitumen, typically asphalt or coal tar
  • Blisters: bubbles or holes that can appear on the surface of asphalt roofing after installation
  • Buckle: the result of asphalt shingles not lying flat either from wrinkling of the roofing underlayment or movement of the roof deck
  • Built-up roof: a flat or low-slope roof with multiple layers of asphalt and ply sheets
  • Bundle: an individual package of roofing shingles; there are typically 3, 4, or 5 bundles per roofing square (100 square feet)
  • Butt edge: the lowest edge of each shingle tab
  • Cant Strip: a strip of wood or similar material that serves as a transitional plane between the horizontal surface of a roof deck and a vertical surface
  • Caulk: a sealant material used to fill a joint to prevent leaks
  • Chalk line: a temporary line drawn on a roof used for alignment purposes, made by snapping a string or cord dusted with chalk
  • Class “A”: the highest rating for fire-resistance for roofing, as determined per ASTM E108; this rating indicates that a roof can withstand extreme exposure to fire starting from a source outside the building
  • Class “B”: fire-resistance rating that means roofing materials can withstand moderate exposure to fire starting from sources outside the building
  • Class “C”: fire-resistance rating that means roofing materials can withstand light exposure to fire arising from sources outside the building
  • Class 4 Impact Resistant shingle: shingles that achieve the roof industry’s highest ratings for impact resistance, UL 2218. Homeowners often qualify for an insurance premium discount.
  • Coating: a fully adhered, fluid applied roofing membrane applied on top of an existing flat-roof product to solve roof leaks and extend the life of an existing roof
  • Collar: a pre-formed rubber or metal flange inserted on top of a vent pipe to seal the roof around the pipe opening
  • Condensation: water which collects on a surface when warm, moist air comes in contact with a cold surface
  • Coping: the top covering of an exterior roof wall, typically made of metal, masonry, or stone
  • Counterflashing: the portion of flashing attached to a vertical surface to prevent water damage
  • Course: a row of shingles that extends the length of a roof
  • Cricket: a ridge construction at the back of a chimney designed to help deflect water away from a chimney
  • Deck: the surface installed over the roof frame to which roofing is applied
  • Dormer: a window that projects vertically from a sloping roof
  • Downspout: a pipe designed to drain water from roof gutters
  • Drip edge: a non-corrosive metal used along a roof’s eaves and rakes to allow water runoff to drip clear of the underlying construction
  • Eaves: the horizontal edge of a sloped roof, typically where gutters exist
  • Elastomeric Coating: a roof coating that is approximately ten times thicker than paint and forms an incredibly dense, yet flexible, cover that helps waterproof the exterior of a structure
  • EPDM: Ethylene Propylene Diene Monomer, a synthetic rubber used in a range of applications including flat roof cover material
  • Fascia: a board that runs along the lower edge of the roof
  • Felt: a fibrous material that acts as an underlayment immediately above the roof deck
  • Fiberglass mat: an asphalt roofing material manufactured with glass fibers
  • Flashing: a piece of metal used to prevent unwanted water entry into a building at any roof intersection, such as vent pipes, chimneys, and valleys
  • Gable: the vertical triangular end of a building from the eaves to the ridge
  • Gable roof: a roof type with a sloping plane on each side of a single ridge and a gable at each end
  • Granules: ceramic-coated colored crushed rock adhered to the exposed surface of asphalt roofing shingles
  • Gutter: a trough that acts as a water distribution system to remove water from the roof eaves into the downspouts
  • Hip: the inclined external angle formed at the intersection of two sloping roof planes, which extends from the eaves to the ridge
  • Hip roof: a roof type where all sides slope downwards to the walls; a hip roof has no gables or vertical sides to the roof
  • Hip shingles: shingles installed to cover the inclined external angle formed at the intersection of two sloping roof planes
  • Ice dam: a condition formed at the lower roof edge by the thawing and refreezing of melted snow on the overhang that can force water up and under shingles, causing leaks
  • Laminated shingles: shingles with multi-dimensional layers to create extra thickness; also called architectural or dimensional
  • Low slope application: the method of installing asphalt shingles on roof slopes between two and four inches per foot
  • Louver: a slanted opening for ventilation
  • Mastic: a roofing product used to seal a roof so water cannot penetrate. Several different kinds of products referred to as mastic; generally speaking, roof mastics are sticky, drying to a soft, rubbery finish after they are applied and allowed to cure.
  • Metal flashing: an accessory component fabricated from sheet metal and used to weatherproof terminating roof covering edges, typically used with cap flashing (coping), counterflashing, step flashing, etc.
  • Mil: a unit of measure often used to indicate the thickness of a roofing membrane
  • Mineral-surfaced roofing: asphalt shingles and roll roofing covered with granules
  • Modified bitumen: a roof coating made of bitumen using special combinations of polymers to modify the underside of the sheet
  • Natural ventilation: a ventilation system utilizing ventilators in an attic to leverage the natural airflow to remove hot or moist interior air and replace it with fresh outside air
  • Normal-slope application: the roofing installation method on roof slopes between 4 inches and 21 inches per foot
  • Open valley: the method of valley construction in which shingles on both sides of a valley get trimmed, and the valley flashing is exposed
  • Organic felt: a roofing base material manufactured from cellulose fibers
  • Parapet wall: the extension of a wall at the edge of the roof that extends above the roof
  • Pitch: the measurement degree of roof incline expressed as the ratio of rise over run, in feet
  • Ply: the number of layers of roofing
  • Ponding: water accumulation at low-lying areas on a roof
  • Rafter: the supporting framing immediately beneath the roof deck, sloping from the ridge to the wall
  • Rake: the inclined edge of a roof, from the eave edge to the ridge
  • Ridge: the highest point on a roof represented by a horizontal line where two opposing roof areas intersect
  • Ridge vent: a roof vent positioned at the ridge that allows warm or moist air to escape from the attic area
  • Ridge shingles: shingles installed to cover the horizontal ridgeline
  • Rise: the vertical distance from a roof eave to the ridgeline
  • Roll roofing: asphalt roofing material that is manufactured and installed in roll form
  • Run: the horizontal distance from a roof eave to a point directly under the ridge
  • Sheathing: a strong layer of wood boards fixed to a roof’s joists and trusses; also known as roof decking
  • Shingle: an individual unit of prepared roofing material designed for installation in overlapping rows or courses on inclines typically exceeding 3:12 slope
  • Slope: the measurement in degrees of roof incline expressed as the ratio of the rise over run
  • Soffit: the finished underside of the eaves
  • Square: a unit of roof measurement; one roofing square is equal to 100 square feet
  • Starter course: the first layer of roofing installed adjacent to the lowest perimeter of the roof area, also known as starter strip. With steep-slope water-shedding roof coverings, the starter course gets covered by the first course.
  • Step flashing: a flashing application that integrates the roof cladding into the exterior wall cladding to prevent water leaks
  • Synthetic underlayment: a premium type of underlayment with an extremely high tear strength compared to felt, which means less tearing around fasteners during roof installation and fewer opportunities for water infiltration
  • Tab: the exposed portion of three-tab or strip shingles defined by cutouts
  • Three-tab shingle: a single-layer shingle which has three tabs and a uniform appearance
  • UL: Underwriters Laboratories, LLC
  • Underlayment: a layer of felt that provides an additional moisture-resistant layer between the roof deck and roof shingles
  • Valley: the angle formed where two roof slopes meet where water collects to flow off the roof
  • Vent: a device installed on a roof that protrudes through the roof deck, such as a pipe or stack, to ventilate the underside of the roof deck
  • Woven valley: the method of valley construction in which shingles from both sides of the valley get woven together