Roofing & exterior terms, explained
Plain-English definitions of the roofing, siding, gutter, and attic terms you'll hear on an estimate — so you can ask sharper questions.
How to use this glossary
Use these definitions to decode estimates, compare options, and understand what matters on your roof before you book. Each term connects to Learn and Evaluate guides so you can move from terminology to real-world decisions.
Roof decking (sheathing)
The flat wood layer nailed across the rafters or trusses that everything else on the roof attaches t…
Define → RoofingOSB (oriented strand board)
An engineered wood panel made from compressed wood strands, commonly used as roof decking. It's stro…
Define → RoofingUnderlayment
A water-resistant layer rolled over the decking beneath the shingles, providing a secondary barrier …
Define → RoofingIce-and-water shield
A self-sealing waterproof membrane applied along eaves, valleys, and penetrations. In Rochester's fr…
Define → RoofingDrip edge
A metal strip installed along the roof's edges that directs runoff into the gutters and away from th…
Define → RoofingFlashing
Thin metal pieces installed at roof joints, walls, and penetrations to seal out water where shingles…
Define → RoofingStep flashing
Overlapping L-shaped metal pieces woven into the shingles where a roof meets a vertical wall, such a…
Define → RoofingValley
The V-shaped channel where two roof slopes meet. It carries a heavy volume of runoff, so it's lined …
Define → RoofingRidge
The horizontal peak line where two roof slopes meet at the top. It's the highest point of the roof a…
Define → RoofingRidge vent
A continuous vent installed along the roof's peak that lets hot, moist attic air escape. Paired with…
Define → RoofingRidge cap
Specially shaped shingles that cover the ridge and hips to seal the peak and give the roofline a fin…
Define → RoofingStarter strip
A row of adhesive-backed shingles installed along the eaves and rakes before the main field. It lock…
Define → RoofingEave
The lower edge of a roof that overhangs the exterior wall, usually where the gutters hang. It's the …
Define → RoofingRake
The sloped edge of a roof that runs from the eave up to the ridge at a gable end, finishing the side…
Define → RoofingGable
The triangular section of wall formed where two roof slopes meet at a ridge. A gable roof is the cla…
Define → RoofingHip
The outward-sloping ridge where two adjacent roof faces meet. A hip roof slopes down on all sides, m…
Define → RoofingDormer
A framed structure that projects out from a sloped roof, usually housing a window. Dormers add headr…
Define → RoofingSkylight
A glazed opening built into the roof to bring in daylight. Proper flashing and curb installation are…
Define → RoofingSquare
A roofing unit of measure equal to 100 square feet. Roofs are priced and ordered by the square, so a…
Define → RoofingPitch (slope)
How steep a roof is, expressed as inches of vertical rise per 12 inches of horizontal run (for examp…
Define → RoofingAsphalt shingle
The most common residential roofing material, made of a fiberglass mat coated in asphalt and mineral…
Define → RoofingArchitectural (dimensional) shingle
A laminated, multi-layer asphalt shingle that gives a thicker, dimensional look and typically carrie…
Define → Roofing3-tab shingle
A flat, single-layer asphalt shingle with three evenly spaced tabs that creates a uniform, lower-cos…
Define → RoofingStanding seam metal roof
A metal roofing system of interlocking vertical panels whose raised seams hide the fasteners. It she…
Define → RoofingGranule loss
The shedding of the protective mineral granules from asphalt shingles, often seen as grit in the gut…
Define → RoofingBlistering
Small raised bubbles on a shingle's surface caused by trapped moisture or poor attic ventilation. Wh…
Define → RoofingCurling
When shingle edges lift or cup upward, usually from age, heat, or inadequate attic ventilation. Curl…
Define → RoofingPonding water
Standing water that lingers on a low-slope or flat roof more than 48 hours after rain. Prolonged pon…
Define → RoofingEPDM membrane
A durable synthetic rubber membrane used on flat and low-slope roofs, installed in large sheets. It'…
Define → RoofingTPO membrane
A single-ply, heat-welded flat-roof membrane with a reflective white surface that lowers cooling loa…
Define → RoofingTear-off
Stripping the old roofing down to the decking before installing a new roof. It costs more than a roo…
Define → RoofingRoof-over (overlay)
Installing new shingles over the existing layer instead of tearing it off. It's cheaper and faster b…
Define → ExteriorGutter
The channel mounted along the eaves that collects roof runoff and routes it to the downspouts, prote…
Define → ExteriorDownspout
The vertical pipe that carries water from the gutters down to the ground and away from the foundatio…
Define → ExteriorGutter guard
A cover or screen fitted over the gutters to keep out leaves and debris while letting water through,…
Define → ExteriorSoffit
The underside of the roof overhang that closes off the gap between the eaves and the wall. Vented so…
Define → Home PerformanceSoffit vent
An intake vent in the soffit that draws cool outside air into the attic. Paired with a ridge vent, i…
Define → ExteriorFascia
The horizontal board running along the roof's lower edge that caps the rafter ends and supports the …
Define → ExteriorFascia board
The actual trim board behind the fascia covering, often wood, that the gutters fasten to. When it ro…
Define → ExteriorVinyl siding
A low-maintenance plastic cladding that's affordable and never needs painting. It's the most common …
Define → ExteriorFiber cement siding
A durable siding made of cement, sand, and cellulose fibers that resists rot, fire, and insects. It …
Define → ExteriorHouse wrap
A breathable weather-resistant barrier wrapped around the sheathing behind the siding. It blocks win…
Define → Home PerformanceIce dam
A ridge of ice that forms at the roof's edge when heat escaping into the attic melts snow that refre…
Define → Home PerformanceAttic ventilation
A balanced system of intake and exhaust vents that keeps attic air moving. Good ventilation extends …
Define → Home PerformanceR-value
A measure of how well insulation resists heat flow — the higher the R-value, the better the insulati…
Define → Home PerformanceVapor barrier
A material that limits moisture from passing through walls or ceilings into the insulation and struc…
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