Roofing Terminology 101

Whether you are planning a DIY project or working with a professional roofer, the sheer number of terms out there may be daunting. The following list contains both common and uncommon terms, alphabetized and broken into categories to make it easier for you to find a specific term quickly.

Descriptive Terms

Absorption: the ability to absorb moisture or gasses, often used when discussing the rate of or resistance to absorbing.

Adhesion: used to describe how well certain materials, such as asphalt, contact cement, and roofing cement can hold two surfaces together.

Aging: the effects over time on materials; may also be used to describe weathering and erosion.

Alligatoringcracks on surface bitumen that resemble alligator skin and may or may not go through the bitumen layer.

Back Surfacing: granular material found on the back of shingles to help keep them separated during storage or transport.

Blister: bubble in a roof membrane caused by air, water, and/or solvent vapor; also known as blackberries, blueberries, and tar-boils.

Blow-Off: shingle torn from a roof deck by high winds.

Buckle: wrinkle or ripple in a membrane or shingles; may indicate movement within the roof’s assembly.

Cupping: defective, over-exposed, or improperly installed shingles which have warped into a curl or cup.

End Laps: area where a rolled roofing product ends and the next rolled section overlaps.

Exposure: describes any roofing material which remains exposed to the elements.

Fasteners: nails and staples that connect the roof to the deck.

High-Nailing: shingles nailed above the manufacturer’s nail marks.

Ice Dam: re-frozen snow runoff along the eaves which causes water to back-up under the shingles.

Overdriven: Fasteners are driven too forcefully, breaking the material.

Pitch: an important term describing three categories of roof angle which affects what materials and roof types may be used:

  • Flat Roof – pitch is less than 2:12
  • Low Slope – pitch measures between 2:12 and 4:12
  • Steep Slope – pitch measures between 4:12 and 21:12

Telegraphing: uneven surfaces reflected by the overlying shingles.

Underdriven: fasteners not driven flush to the shingle’s surface.

Wind Uplift: changes or drops in air pressure above a roof as wind is deflected by the edges, peaks, or other protrusions; may cause the membrane to pull away from the deck if pressure is introduced under the edges.

Related Organizations

APA: APA – The Engineered Wood Association

ARMA: Asphalt Roofing Manufacturers Association

ASTM: American Society for Testing and Materials

BOMA: Building Owners and Managers Association

EWTA: Engineered Wood Technology Association

NRCA: National Roofing Contracting Association

Roof Components

Aggregate: various types and conditions of rock, such as crushed stone or marble chips, used for surfacing material or ballast.

Angled Fasteners: roofing nails or staples which are driven into the roof deck at an angle.

Apron Flashing: the flashing located where the top of a sloped roof meets a vertical wall, chimney, or a steeper-sloped roof.

Architectural Shingle: shingle which gives the appearance of shape or dimension.

Ballast: gravel, precast concrete pavers, or other materials used to anchor a single-ply roofing membrane in place.

Base Ply: lowest ply in a roof or membrane system.

Counter-Flashing: metal or siding material installed over a base flashing system.

Cricket: peaked diverter which directs water around large roof projections such as chimneys.

Deck: substrate of wooden boards, planks, or plywood upon which the roofing is built.

Dormer: raise section of roof extending from a larger section of roof plane.

Drip Edge: a lip, usually metal flashing, which helps control dripping water and protect the underlying section of wall.

Eaves: the first three feet of a roof, or the area from the edge of the fascia to the outside wall.

Flange: metal pan which extends around the flashing along vents or chimneys.

Flashing: materials placed around the edges of roof projections to waterproof.

Gable: triangular portion of wall between a sloping roof and eave line.

Joist: beams or timbers stretching horizontally between walls to support ceilings or roofs.

L-Flashing: continuous metal flashing along a horizontal wall and bent at a 90 degree angle.

Membrane: either flexible or semi-flexible material that acts as a waterproofing element.

Ply: layer of ply sheet, felt, or reinforcement.

Rafter: support beams upon which the roof deck rests.

Ridge: the horizontal line at the peak of two roof planes.

Roof Plane: A section of roof with four distinct edges.

Soffit: enclosed underside of the eaves, often including an intake vent.

Substrate: the deck or insulation upon which the roofing materials are placed.

Transition: The intersection of two roof panes of different pitches.

Underlayment: asphalt-based rolled materials that add extra protection when laid under the main roofing layers.

Valley: a V-shaped intersection between two roof planes.

Vent: opening to release heat, vapor, or gasses from the inside of a building.

Weep Hole: small drainage openings in components such as skylight frames.

Roofing Techniques

Accelerated Weathering: Materials are exposed to various weather-like effects to prematurely age or erode them. The materials are then compared to unexposed materials to measure changes in the physical properties of the material.

Back/Blind-Nailing: Fasteners are driven into the back of a roofing component such as a ply so that it is covered by the next sequential ply. This keeps the fastener from becoming exposed to weather.

Brooming: Using a broom, squeegee, or other tool, to smooth out a ply an ensure contact with any underlying adhesive.

Closed-Cut Valley: One set of shingles in the valley where two roof planes meet is cut to match the valley lines, completely covering the other set.

Hand-Sealing: This method ensures the sealing of shingles on steep-pitched roofs, during cold weather installation, or in areas with high wind.

Infrared Thermography: An infrared camera is used to record the temperature of a roof. Deviations in the temperature can indicate moist or wet patches of insulation.

Mopping: Hot bitumen is applied to the substrate or membrane using either a roofer’s hand mop or mechanical applicator.

Open Valley: The metal flashing is left exposed instead of covering the valley with shingles.

Woven Valley: Shingles from the connecting roofs are laid atop one another in an alternating pattern.

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