Roofing Glossary
50 roofing terms defined with specifications, measurements, and industry standards. Written by roofing professionals, reviewed for accuracy.
Architectural Shingles
Architectural shingles are defined as multi-layered asphalt shingles that create a dimensional, textured appearance on the roof surface. They are thicker and more durable than three-tab shingles, with a typical lifespan of 25 to 50 years depending on manufacturer and grade.
Read full definition →Asphalt Shingles
Asphalt shingles are defined as the most widely used residential roofing material in North America, comprising a fiberglass or organic mat base coated with asphalt and topped with ceramic-coated mineral granules. They are manufactured in two primary types: three-tab (flat, single-layer) and architectural (dimensional, multi-layer).
Read full definition →Attic Ventilation
Attic ventilation is defined as a system of intake and exhaust openings that allows air to circulate through the attic space, regulating temperature and moisture levels beneath the roof deck. Proper attic ventilation requires a minimum of 1 square foot of net free ventilation area per 150 square feet of attic floor space, or 1:300 if a vapor barrier is installed.
Read full definition →Cap Shingles
Cap shingles are defined as specially manufactured or field-cut shingles installed along the ridge and hip lines of a roof to provide a finished, weatherproof seal at these peak intersections. Factory-made cap shingles such as Owens Corning DecoRidge are typically 9 inches by 33 inches and are designed to match the profile and color of the field shingles.
Read full definition →Counterflashing
Counterflashing is defined as a piece of metal flashing that is embedded into or attached to a vertical surface such as a wall, chimney, or parapet to overlap and protect the top edge of step flashing or base flashing below it. Counterflashing is typically made from aluminum, galvanized steel, or copper and is installed in a reglet (groove) cut into the masonry or mortar joint.
Read full definition →Cricket
A cricket is defined as a small peaked structure built on the backside of a chimney or other roof penetration to divert water and prevent ponding and debris accumulation. The IRC (International Residential Code) requires a cricket on the upslope side of any chimney wider than 30 inches.
Read full definition →Decking
Decking is defined as the structural substrate, typically plywood or oriented strand board (OSB), that is fastened to the roof rafters or trusses and serves as the base surface for the underlayment and roofing materials. Standard roof decking thickness is 7/16-inch OSB or 1/2-inch CDX plywood, though 5/8-inch or 3/4-inch panels are required for wider rafter spacing.
Read full definition →Dormer
A dormer is defined as a roofed structure containing a window that projects vertically from the slope of a main roof, adding usable space, natural light, and ventilation to the attic or upper floor. Common dormer types include shed, gable, hip, and eyebrow.
Read full definition →Drip Edge
Drip edge is defined as an L-shaped metal flashing strip installed along the eaves and rakes of a roof to direct water runoff away from the fascia and into the gutter system. The IRC requires drip edge on all asphalt shingle roofs as of the 2012 code cycle.
Read full definition →Fascia
Fascia is defined as the vertical board or trim piece that caps the exposed ends of the roof rafters along the eave, serving as the mounting surface for the gutter system and the termination point for the drip edge. Fascia is typically made from 1x6 or 1x8 lumber, fiber cement, or aluminum cladding.
Read full definition →Felt Underlayment
Felt underlayment is defined as a traditional asphalt-saturated paper product installed over the roof deck and beneath the shingles to provide a secondary moisture barrier. Available in 15-pound and 30-pound weights per 100 square feet, felt underlayment has been the industry standard for over a century.
Read full definition →Flashing
Flashing is defined as thin pieces of impervious material, typically galvanized steel, aluminum, or copper, installed at roof transitions, penetrations, and intersections to prevent water from entering the building envelope. Common flashing locations include valleys, chimneys, skylights, vent pipes, dormers, and wall-to-roof junctions.
Read full definition →Gable
A gable is defined as the triangular section of wall between the edges of intersecting roof pitches, forming the peaked end of a building. A gable roof is the most common roof shape in residential construction, consisting of two sloping sides that meet at a central ridge.
Read full definition →Gambrel Roof
A gambrel roof is defined as a symmetrical two-sided roof design with two slopes on each side, where the lower slope is steeper than the upper slope. The gambrel design maximizes interior headroom and usable attic space and is commonly associated with barn-style and Dutch Colonial architecture.
Read full definition →Granules
Granules are defined as the ceramic-coated crusite minerals or manufactured mineral particles embedded in the surface of asphalt shingles to protect the underlying asphalt from UV radiation, provide fire resistance, and add color. A single architectural shingle contains approximately 1,500 to 2,000 granules per square inch.
Read full definition →Gutter
A gutter is defined as a horizontal channel installed along the eave of a roof to collect and redirect rainwater away from the foundation of the building. Standard residential gutters are 5 inches (K-style) or 6 inches (half-round) in width and are made from aluminum, copper, galvanized steel, or vinyl.
Read full definition →Ice Dam
An ice dam is defined as a ridge of ice that forms along the eave of a roof when melted snow refreezes at the roof edge, preventing proper drainage and causing water to back up under the shingles. Ice dams occur when the upper roof surface is above 32 degrees F while the eave overhang is below freezing, typically caused by inadequate attic insulation and ventilation.
Read full definition →Ice and Water Shield
Ice and water shield is defined as a self-adhering, rubberized asphalt membrane applied to the roof deck at vulnerable areas to provide a waterproof barrier against ice dams, wind-driven rain, and standing water. Building codes in cold-climate zones require ice and water shield installation from the eave edge to at least 24 inches past the interior wall line.
Read full definition →OSB
OSB (oriented strand board) is defined as an engineered wood panel made from compressed layers of wood strands bonded with waterproof resin adhesive, used as roof decking and wall sheathing. Standard roof-grade OSB is 7/16-inch thick and rated for 24-inch on-center rafter spacing.
Read full definition →Overhang
An overhang is defined as the portion of the roof structure that extends beyond the exterior wall of a building, providing protection from rain, snow, and sun exposure. Roof overhang depth typically ranges from 12 to 24 inches for residential construction and influences the size of the soffit, fascia, and drip edge required during a roof replacement.
Read full definition →Pitch
Pitch is defined as the steepness or angle of a roof, expressed as a ratio of vertical rise to horizontal run. A roof with a 6:12 pitch rises 6 inches for every 12 inches of horizontal distance.
Read full definition →Plywood
Plywood is defined as a wood panel manufactured from thin layers (veneers) of wood glued together with adjacent layers having their grain perpendicular, providing dimensional stability and strength as roof decking material. CDX-grade plywood at 1/2-inch or 5/8-inch thickness is the standard specification for residential roof decking.
Read full definition →R-Value
R-value is defined as the measure of a material's thermal resistance, indicating its ability to resist heat flow. In roofing, R-value applies to the insulation installed in the attic space beneath the roof deck.
Read full definition →Rafter
A rafter is defined as a structural framing member that runs from the ridge board at the peak of the roof down to the top plate of the exterior wall, supporting the roof decking and shingles. Standard residential rafters are 2x6, 2x8, or 2x10 lumber, sized based on span length, load requirements, and local building codes.
Read full definition →Rake
A rake is defined as the inclined edge of a sloped roof that runs from the eave to the ridge along the gable end of the building. The rake edge requires a drip edge and is finished with rake trim or rake board to protect the roof edge from wind-driven rain and to provide a clean aesthetic line.
Read full definition →Ridge
A ridge is defined as the horizontal line formed at the intersection of two opposing sloped roof surfaces at the highest point of the roof. The ridge is the longest structural span of a roof and is supported by a ridge board or ridge beam.
Read full definition →Ridge Cap
A ridge cap is defined as the finished covering installed over the ridge and hip lines of a roof, consisting of specially designed shingles or metal trim that seals the joint where two roof planes meet. Factory-manufactured ridge cap shingles like Owens Corning DecoRidge provide a thicker, more uniform profile than field-cut shingles.
Read full definition →Ridge Vent
A ridge vent is defined as a continuous ventilation component installed along the entire ridge of a roof to allow warm, moist air to escape from the attic space through the natural convection process known as the stack effect. Ridge vents provide 18 square inches of net free area per linear foot and work in conjunction with soffit vents to create balanced attic ventilation.
Read full definition →Roof Deck
A roof deck is defined as the complete structural surface of a roof, consisting of the sheathing panels (plywood or OSB) fastened to the rafters or trusses, onto which the underlayment and roofing materials are applied. The condition of the roof deck is assessed during tear-off and any damaged, delaminated, or water-damaged sections must be replaced before new materials are installed.
Read full definition →Roof Square
A roof square is defined as a unit of measurement used in roofing that equals 100 square feet of roof surface area. A 2,000-square-foot roof is 20 squares.
Read full definition →Roof Truss
A roof truss is defined as a pre-engineered structural framework of interconnected triangular units designed to support the roof load and span the width of the building without interior load-bearing walls. Trusses are manufactured off-site to precise specifications and installed as complete units, replacing traditional stick-framed rafter systems in most modern residential construction.
Read full definition →Saturated Felt
Saturated felt is defined as an organic or fiberglass mat that has been impregnated with asphalt to create a water-resistant underlayment for use beneath roofing materials. Available in 15-pound and 30-pound weights (per 100 square feet), saturated felt has been used in roofing applications for over 100 years.
Read full definition →Sheathing
Sheathing is defined as the layer of boards or panels (plywood or OSB) fastened to the roof rafters or trusses to form the structural roof deck. The terms sheathing and decking are used interchangeably in residential roofing.
Read full definition →Shingle
A shingle is defined as an individual overlapping element used as the primary weather-resistant covering on a sloped roof. While shingles can be made from various materials including wood, slate, tile, and metal, the term most commonly refers to asphalt shingles in residential construction.
Read full definition →Slope
Slope is defined as the incline of a roof surface, expressed as inches of rise per foot of horizontal run. Slope and pitch are often used interchangeably in residential roofing, though technically pitch refers to the ratio of rise to the full span.
Read full definition →Soffit
Soffit is defined as the finished underside of the roof overhang, spanning from the exterior wall to the fascia board at the eave. Soffits are typically constructed from vinyl, aluminum, fiber cement, or plywood and serve the critical function of housing intake ventilation ports that draw fresh air into the attic.
Read full definition →Soffit Vent
A soffit vent is defined as an intake ventilation opening installed in the soffit panels beneath the roof overhang to allow fresh outside air to enter the attic space. Soffit vents work in conjunction with ridge vents or other exhaust vents to create continuous airflow through the attic.
Read full definition →Starter Strip
A starter strip is defined as a row of shingles or a continuous roll of shingle material installed along the eave and rake edges before the first course of field shingles, providing a sealed adhesive bond and a waterproof barrier at the most wind-vulnerable areas of the roof. Factory-made starter strips like Owens Corning StarterStrip Plus feature a pre-applied sealant line that bonds to the first course of shingles.
Read full definition →Step Flashing
Step flashing is defined as individual pieces of L-shaped metal flashing woven into each course of shingles where the roof meets a vertical sidewall, chimney, or dormer. Each piece of step flashing is typically 5x7 inches and is installed so that it overlaps the piece below it by at least 2 inches, creating a cascading water barrier.
Read full definition →Synthetic Underlayment
Synthetic underlayment is defined as a woven or non-woven polypropylene or polyethylene sheet material installed over the roof deck as a secondary moisture barrier beneath the shingles. Synthetic underlayment has largely replaced traditional felt underlayment due to its superior tear strength (up to 10x stronger), UV resistance (up to 6 months of exposure), lighter weight, and lay-flat characteristics.
Read full definition →Tab
A tab is defined as the exposed portion of a shingle that is visible after installation, as distinguished from the headlap portion that is covered by the course above. In a three-tab shingle, the cutouts between tabs create the appearance of three separate pieces from a single shingle strip.
Read full definition →Tear-Off
A tear-off is defined as the process of removing all existing roofing materials down to the roof deck before installing a new roof system. A complete tear-off involves stripping shingles, underlayment, flashing, and any deteriorated decking.
Read full definition →Three-Tab Shingles
Three-tab shingles are defined as single-layer asphalt shingles with two cutouts that create the appearance of three individual tabs per shingle strip. Three-tab shingles are 12 inches by 36 inches and produce a flat, uniform appearance.
Read full definition →Valley
A valley is defined as the internal angle formed where two sloping roof planes intersect, creating a channel that concentrates and directs water runoff toward the gutters. Valleys are one of the highest-volume water channels on a roof and are waterproofed with ice and water shield membrane covered by either metal valley flashing (open valley) or overlapping shingles (closed-cut or woven valley).
Read full definition →Vent Pipe Boot
A vent pipe boot is defined as a pre-formed flashing assembly consisting of a metal base plate with an integrated rubber or neoprene collar that seals around plumbing vent pipes where they penetrate the roof surface. Standard vent pipe boots accommodate pipe diameters from 1-1/2 inches to 4 inches.
Read full definition →Know the terms. Know your price.
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