Roofing estimates are written in a trade language, and contractors know most homeowners cannot read it. When you understand basic roofing terms — square, pitch, flashing, underlayment, decking — you can compare bids line by line, spot padded quotes, and ask questions that tell a salesman you cannot be steamrolled. A “square” alone confuses more homeowners than any other word in the business, and it appears on every single estimate. This glossary covers the vocabulary that actually shows up in quotes, inspections, and insurance claims, organized the way a roof is built: from the structure up.
Part of our Roofing guide — explore the full guide →
Measurement and Geometry Terms
A square is 100 square feet of roof area — the universal pricing unit. A 2,400-square-foot roof is a 24-square job, and shingles are sold in bundles, usually three bundles per square. Pitch (or slope) describes steepness as rise over a 12-inch run: a 4/12 roof rises 4 inches per horizontal foot. Anything below 2/12 is considered low-slope and needs membrane roofing rather than shingles; above roughly 8/12, crews add steep-slope labor charges of 20 to 40 percent because everything must be done from staging or harnesses.
The geometry words describe where roof planes meet. The ridge is the horizontal peak. A hip is an external corner where two planes slope together; a valley is the internal channel where they drain together, and valleys carry more water than any other spot on the roof. Eaves are the lower horizontal edges that overhang the walls, while rakes are the sloped edges at gable ends. A dormer is a small roofed projection with a window, and every dormer adds flashing complexity — and cost.
Structure and Deck Terms
Under the shingles sits the skeleton. Rafters are sloped framing members cut on site; trusses are factory-engineered triangulated frames, standard in homes built after about 1970, usually spaced 24 inches on center. The decking or sheathing — typically 7/16-inch OSB or 1/2-inch CDX plywood — spans the framing and gives nails something to bite. When a bid includes “re-deck” or per-sheet decking allowances of $65 to $120, this is the layer being replaced.
The fascia is the vertical trim board at the eaves where gutters hang, and the soffit is the horizontal underside of the overhang, usually vented to feed air into the attic. Rot in either is common collateral damage from clogged gutters and shows up as a line item on thorough estimates.
The Waterproofing Layers
Modern roofs are systems, and the layers matter more than the shingles. Underlayment is the water-shedding sheet between decking and shingles — traditionally 15-pound or 30-pound asphalt felt, now more often a synthetic like GAF FeltBuster or Owens Corning ProArmor that resists tearing and can stay exposed for weeks. Ice and water shield is a self-adhering rubberized membrane applied at eaves, valleys, and penetrations; code in cold climates requires it to extend at least 24 inches past the interior wall line to defend against ice dams.
Flashing is the metal that waterproofs transitions. Step flashing consists of L-shaped pieces woven into each shingle course along walls and chimneys. Counterflashing is embedded in chimney mortar and laps over step flashing. A pipe boot seals plumbing vents, and cracked neoprene boots cause a huge share of small roof leaks. Drip edge is the angled metal at eaves and rakes that kicks water into the gutter instead of behind the fascia — required by the IRC since 2012 and still missing from lowball bids.
Shingle Vocabulary
Shingle estimates carry their own terms worth decoding:
- Three-tab: flat, single-layer shingles with cutout tabs; the budget option, roughly $90 to $110 per square in materials, with 60 to 70 mph wind ratings.
- Architectural (dimensional/laminate): layered shingles with a textured profile — the current standard, $110 to $160 per square, typically rated 110 to 130 mph.
- Starter strip: a purpose-made first course at eaves and rakes that seals shingle edges against wind lift; crews cutting up three-tabs instead is an old shortcut.
- Hip and ridge cap: shaped shingles that cover peaks; matching designer caps cost extra but finish the roof properly.
- Sealant strip: the factory adhesive line that heat-activates and bonds courses together — the reason new roofs should experience a few warm days before a windstorm.
- Granules: the ceramic-coated mineral surface protecting asphalt from UV; heavy granule loss in gutters signals an aging roof.
Ventilation and Attic Terms
Ventilation vocabulary matters because bad airflow quietly kills roofs. A ridge vent is a continuous exhaust slot at the peak; soffit vents supply intake air at the eaves; together they should meet the code minimum of 1 square foot of net free area per 300 square feet of attic (with balanced intake and exhaust) or 1 per 150 otherwise. Baffles are foam or cardboard chutes that keep insulation from blocking soffit airflow. An ice dam forms when attic heat melts snow that refreezes at the cold eaves, ponding water under shingles — a ventilation and air-sealing problem more than a shingle problem.
You may also see gable vents (in end walls), turbine vents (“whirlybirds”), and powered attic fans. Mixing exhaust types can short-circuit airflow, which is why good roofers standardize on one exhaust system.
Estimate and Insurance Terms
Paperwork has its own dialect. Tear-off means removing existing roofing to the deck; an overlay or nail-over installs new shingles over old, capped by code at two total layers. A waste factor — usually 10 to 15 percent — covers cutting losses on hips and valleys. On insurance claims, ACV (actual cash value) pays the depreciated worth of your old roof, while RCV (replacement cost value) pays full replacement, releasing recoverable depreciation after the work is done. A supplement is a contractor’s request for added scope the adjuster missed, and Xactimate is the pricing software both sides use.
Watch for exclusions in contracts: decking replacement, flashing reuse, and permit fees are the three places cheap bids hide costs.
Metal and Low-Slope Roof Terms
Metal roofing brings its own dialect. Standing seam panels join at raised vertical ribs with concealed clips, so no fasteners penetrate the weather surface; exposed-fastener panels (corrugated, R-panel, 5V) screw straight through with gasketed screws that need retightening every decade or so. Gauge describes steel thickness — 24-gauge is heavier and flatter-looking than 26 or 29 — and Galvalume is the aluminum-zinc coating that protects the steel beneath the paint. Oil canning names the wavy distortion visible on wide flat panels in raking light; it is cosmetic, common, and reduced by striations or heavier gauge.
Flat and low-slope roofs over porches and additions use membrane vocabulary. EPDM is black rubber sheet, TPO is white heat-welded thermoplastic, and modified bitumen is asphalt sheet applied in torch-down or peel-and-stick rolls. Ponding — water still standing 48 hours after rain — is the defect inspectors flag, and tapered insulation is the usual cure. Knowing these dozen words matters even on a shingle house, because the porch roof is often where the estimate hides its weakest detail.
Terms That Signal Trouble
A few phrases deserve heightened attention when you hear them. “We’ll reuse your existing flashing” often means water problems in five years, since old flashing rarely matches new shingle thickness. “No permit needed” is almost never true for a full replacement. “Storm chaser” describes out-of-town crews who follow hail events, collect deductibles, and vanish before warranty calls. And “lifetime warranty” refers to a prorated limited manufacturer warranty with registration requirements — ask specifically what is covered in year 15, and get the workmanship warranty (the one covering installation errors, ideally 5 to 10 years) in writing.
Learn these roofing terms once and every future conversation gets easier. When you can ask a bidder whether the price includes new drip edge, ice and water shield to code, and starter strip at the rakes, you have already filtered out half the bad actors in the market.
