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Roofing Terms Glossary
Roofing has a language all its own, and it is easy to feel lost when an estimate mentions decking, drip edge, or ice-and-water shield. This plain-English roofing terms glossary explains more than 30 of the words you will actually hear during an inspection, estimate, or insurance claim in South Carolina — so you can make a confident, informed decision about your roof. When you want a real answer for your specific home, 247 Roofs is a phone call away.
How to Use This Glossary
Understand Your Roof Before You Sign Anything
Whether you are comparing estimates, reviewing a storm-damage report, or just trying to follow along during a roof inspection, knowing the vocabulary puts you in control. The terms below are grouped alphabetically and written the way we would explain them to a neighbor. If a word on your estimate is not here, call us and we will explain it — a good roofer should never leave you guessing.
A – F
Roofing Terms: A to F
Architectural shingle — A thicker, layered asphalt shingle (also called dimensional or laminate) that looks like slate or wood shakes and typically lasts 25–30 years. The most popular choice on South Carolina homes.
Asphalt shingle — The common roofing material made of a fiberglass mat coated in asphalt and protective granules. Sold in basic 3-tab and upgraded architectural styles.
Counterflashing — A second layer of flashing set into a wall or chimney that covers the top edge of the base flashing, directing water away from the joint.
Decking (sheathing) — The plywood or OSB boards nailed to the rafters that form the solid surface your roof is built on. Rotted decking is replaced during a re-roof.
Drip edge — A metal strip installed along the eaves and rakes that guides water off the roof and into the gutters instead of behind them, protecting the fascia and decking.
Eave — The lower edge of the roof that overhangs the exterior wall, usually where the gutters are mounted.
Fascia — The vertical board running along the eave that caps the rafter ends and holds the gutters. See our gutters page for how it works with your drainage.
Felt — Traditional asphalt-saturated underlayment rolled over the decking before shingles. Increasingly replaced by synthetic underlayment.
Flashing — Thin metal pieces installed at roof joints, valleys, chimneys, and around skylights to seal out water where the roof plane changes direction. Failed flashing is one of the most common leak sources.
G – P
Roofing Terms: G to P
Gable — The triangular section of wall at the end of a ridged roof; a simple “gable roof” is the classic two-sloped shape.
Granules — The ceramic-coated mineral particles on a shingle’s surface that shield the asphalt from UV rays. Hail knocks granules loose, which is a key sign of storm damage.
Hip — The outward-sloping ridge where two roof planes meet; a hip roof slopes down on all four sides.
Ice-and-water shield — A self-adhering waterproof membrane applied at vulnerable spots like eaves and valleys to block wind-driven rain and leaks.
Membrane — A single-ply waterproof sheet (TPO, EPDM, PVC) used on flat and low-slope roofs, common on commercial buildings. See commercial roofing.
Pitch (slope) — How steep the roof is, expressed as inches of rise per 12 inches of run (e.g., 6/12). Steeper pitches cost more to install and shed water faster.
Ply / plywood — A common form of roof decking; “OSB” (oriented strand board) is the other. Both can rot if water gets past the shingles.
R – Z
Roofing Terms: R to Z
Rafter — The angled structural beams that support the decking and give the roof its shape.
Rake — The sloped edge of a roof at a gable end, running from eave to ridge.
Ridge — The horizontal peak where two roof slopes meet at the top. Covered by ridge caps and often vented.
Ridge vent — A vent along the ridge that lets hot attic air escape, part of a balanced ventilation system that extends shingle life in South Carolina’s heat.
Soffit — The underside of the roof overhang, usually vented to pull cool air into the attic and work with the ridge vent.
Square — The roofing unit of measure equal to 100 square feet (a 10 ft × 10 ft area). Roofs are priced and ordered by the square. Our roofing cost guide explains how squares affect price.
Standing seam — A premium metal roof system with raised, interlocking vertical seams and hidden fasteners; lasts 40–70 years. See metal roofing.
Tear-off — Removing the old roofing down to the decking before installing new material, versus laying new shingles over the old (an overlay).
Underlayment — The protective layer (synthetic or felt) between the decking and the shingles that adds a second line of defense against water.
Valley — The internal angle where two roof slopes meet and channel water; a common leak point that needs careful flashing.
Vent boot (pipe boot) — The rubber or metal seal around a plumbing vent pipe where it exits the roof. Cracked boots are a frequent, easy-to-miss leak source.
Wind rating — The tested wind speed a roofing product can withstand (e.g., 130 mph). Critical for coastal Charleston and Grand Strand homes facing hurricanes.
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Glossary FAQ
Common Roofing-Term Questions
What is a “square” in roofing?
A square equals 100 square feet of roof area (a 10 ft by 10 ft section). Roofers measure, price, and order materials by the square, so a roof described as “24 squares” has about 2,400 square feet of surface.
What is the difference between decking and underlayment?
Decking is the solid plywood or OSB surface nailed to the rafters — the structural base of the roof. Underlayment is the thin waterproof layer rolled on top of the decking, under the shingles, as a second line of defense against water.
Why does flashing matter so much?
Flashing seals the spots where the roof plane changes — valleys, chimneys, walls, and around skylights and vents. Because those joints are where water naturally tries to get in, failed or missing flashing is one of the most common causes of roof leaks.
What is the difference between a tear-off and an overlay?
A tear-off removes the old roofing down to the decking before installing new material, which lets us inspect and replace any rotted wood. An overlay lays new shingles over the old ones — cheaper up front, but it hides problems and usually shortens the new roof’s life. We recommend a tear-off in most cases.
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