Roofing Terms Explained: A Homeowner Glossary

Roof structure and anatomy terms

These describe the physical parts of your roof. Contractors use them constantly and rarely stop to explain them.

• Deck: the structural surface, usually plywood or OSB, that everything else is fastened to. "Decking" usually means the sheet material itself, though most contractors use the two words interchangeably.
• Rafter: a sloped framing member running from ridge to eave.
• Truss: a pre-engineered triangulated frame used instead of site-built rafters. Worth knowing because trusses generally cannot be cut or altered without an engineer.
• Ridge: the horizontal line at the top where two roof planes meet.
• Hip: the sloped outside angle where two roof planes meet.
• Valley: the inside angle where two planes meet and funnel water.
• Eave: the lower edge of a roof plane, usually overhanging the wall.
• Rake: the sloped edge of the roof at a gable end.
• Fascia: the vertical board along the eave that usually carries the gutter.
• Soffit: the underside of the roof overhang, often vented to let intake air in.
• Dormer: a framed projection with its own small roof, set into a slope.
• Penetration: anything passing through the roof plane, such as a pipe, vent, chimney, or skylight.

For a visual walkthrough of how these fit together, see the parts of a roof explained.

Material terms

• Three-tab shingle: the original flat, single-layer asphalt shingle. CertainTeed describes it as the most basic type, named for how the shingle is cut.
• Architectural, dimensional, or laminate shingle: all three words mean the same product, made with two or more asphalt layers fused for a thicker look. Nobody should charge you more for calling it architectural.
• Luxury shingle: the top laminated tier, with a distinct appearance or performance above dimensional.
• Underlayment: the layer between deck and shingles. Building code requires it to meet specific ASTM standards. Many contractors still call it "felt" or "paper" even when what they install is synthetic.
• Ice barrier: a specific waterproof membrane at the eaves. See the misunderstood section below, because this one has a code-defined geometry that catches people out.
• Starter strip: the first row installed at the eave and often along the rakes, which improves wind resistance.
• Hip and ridge cap: shingles made or cut specifically to cover hips and ridges.
• Granules: the ceramic-coated mineral surface that gives a shingle its color and shields the asphalt from UV.

Sources for the shingle grades: CertainTeed on types of asphalt shingles. For a deeper comparison see architectural vs 3-tab shingles and roof underlayment types.

Slope, pitch, and why low-slope costs more

Slope is expressed as vertical rise per 12 units of horizontal run, like 6:12. The residential code permits asphalt shingles only on slopes of 2:12 or greater.

Between 2:12 and 4:12 the code requires a double layer of underlayment. At 4:12 and above a single layer is allowed. That is a real cost difference, and it is a line item worth checking if your roof is shallow.

Strictly speaking, pitch and slope are not the same thing: slope is rise over 12 units of run, while pitch is rise over the total span. In practice essentially every US contractor says pitch when they mean slope, and you should read it that way.

Slope rules and underlayment requirements: IRC Chapter 9, Roof Assemblies.

Water management and flashing terms

• Flashing: metal installed where the roof meets something else, to keep water out. Code requires it at wall intersections and valleys.
• Step flashing: individual L-shaped pieces woven into each shingle course where a roof meets a vertical wall.
• Counterflashing: the upper piece, usually set into masonry, that laps over the base flashing.
• Kick-out flashing: a small diverter at the bottom of a roof-to-wall junction that throws water clear of the siding. It is frequently left off, and its absence is a classic cause of hidden wall rot.
• Drip edge: metal at the eaves and rakes. Code requires it, and specifies that it extend at least 1/4 inch below the sheathing and at least 2 inches back onto the deck, with laps of at least 2 inches.
• Cricket or saddle: a small peaked structure behind a chimney that splits water around it.
• Pipe boot: the flashing collar that seals a round pipe penetration. A common leak point as the rubber ages.

The four valley types, and why they are not interchangeable

• Open valley: metal runs down the valley and the shingles are cut back on both sides, leaving metal exposed.
• Closed-cut valley: shingles from one plane run past the center, the other plane overlaps and is cut in a straight line about two inches off center.
• Woven valley: shingles from both planes are laced together through the valley. Difficult with stiff laminate shingles.
• California valley: a variant of the open metal valley with shingles run parallel to the centerline alongside the flashing.

This matters for more than looks. IKO recommends open metal valleys and states that other valley types are not covered by its limited warranty. Check what your own shingle manufacturer says: IKO on open versus closed valleys. More detail in our guide to roof valley types.

Ventilation terms

• Net free ventilating area: the actual open area of a vent once screens and louvers are subtracted. Vents are rated this way, not by their overall size.
• The 1/150 rule: code sets minimum ventilating area at 1/150 of the vented space.
• The 1/300 exception: 1/300 is allowed only when both required conditions are met, including that 40 to 50 percent of the venting sits in the upper portion of the attic with the balance in the bottom third. It is an exception with conditions, not the default, even though it gets quoted as standard.
• Intake vent: low vents, usually in the soffit, that let air in.
• Exhaust vent: high vents, usually at the ridge, that let air out.
• Baffle: a channel that stops insulation from blocking soffit intake.

Code text: IRC R806.2 on minimum vent area. See also roof ventilation explained.

Insurance and claims terms

This vocabulary decides how much money you actually receive. It is worth more attention than the roofing terms.

• Actual Cash Value (ACV): what it costs to fix your home minus the decrease in value from age and wear. In other words, replacement cost minus depreciation.
• Replacement Cost Value (RCV): what it costs to repair or replace at today prices with materials of like kind and quality, without the depreciation subtracted.
• Depreciation: the decrease in value of your property from age or use.
• Recoverable depreciation: under a replacement cost policy the insurer typically pays the ACV amount first, then reimburses the withheld depreciation once the work is done and you submit receipts.
• Deductible: your out-of-pocket share. Note that wind and hail deductibles are often a percentage of your dwelling coverage, not a flat dollar figure, which makes them much larger than people expect.
• Scope of loss: the adjuster itemized list of damage and required repairs.
• Supplement: a request for additional payment when the real scope turns out bigger than the original estimate.
• Public adjuster: a licensed adjuster you hire, independent of your insurer. Licensing is state-regulated.

Definitions here follow the North Carolina Department of Insurance and the NAIC. Go deeper in actual cash value vs replacement cost and recoverable depreciation explained.

Contract and permit terms

• Home improvement contract: the written agreement describing all labor, services, and materials. Written contracts are required above a dollar threshold in many states, and the threshold varies.
• Right to cancel: many states give you a few business days to back out of a contract signed at your home. The details, the window, and the exceptions are state law, so check your own state rather than assuming.
• Change order: a written amendment covering work added after signing. Verbal change orders are how disputes start.
• Progress payments: paying as work is completed rather than up front. Several states also cap how large a deposit a contractor can take before starting.
• Mechanics lien: a claim that anyone who improved your property but was not paid can place against your home. If your contractor does not pay a supplier or a sub, that party may be able to lien you even though you paid the contractor.
• Lien waiver: a signed release of lien rights in exchange for payment. Some states have mandatory forms, and a non-conforming waiver may not hold up.
• Manufacturer warranty vs workmanship warranty: the first covers product defects and comes from the shingle maker. The second covers installation error and comes from your contractor. They are separate documents with separate terms and separate ways to fail.

Liens are the one to take seriously. See roofing liens explained and roofing warranties explained.

The terms that actually cost people money

If you skim everything else, these are the ones where a misunderstanding has a dollar figure attached.

1. Square vs square foot. A square is 100 square feet. Misreading per-square pricing as per-square-foot pricing makes an honest bid look like a scam, and makes a scam look like a bargain.
2. ACV vs RCV. This single distinction decides whether you get the depreciated value of a worn roof or the cost of a new one. It is the largest dollar swing on any roof claim.
3. Recoverable depreciation. Homeowners see the first check, assume it is the whole settlement, and never file the receipts needed to claim the rest. That money is forfeited by doing nothing.
4. Ice barrier vs underlayment. They are different products. Code requires the ice barrier to run from the lowest roof edge to a point at least 24 inches inside the exterior wall line. That is measured from the wall, not the roof edge, so a deep overhang needs more than one course. "Ice and water shield" is a brand name that became generic, not the code term.
5. The 1/300 ventilation ratio. It is an exception with two mandatory conditions, not the standard. If someone quotes 1/300, ask which conditions your roof meets.
6. Low-slope. Between 2:12 and 4:12 the code requires doubled underlayment. If your roof is shallow and the bid does not mention it, ask.
7. Valley type. Warranty coverage can depend on which one is installed, and the estimate usually just says "valley".
8. Class 4 does not mean hail-proof. Impact-rated shingles resist cracking. They can still dent, and cosmetic denting is often excluded from coverage anyway.

Ask, do not guess

A good contractor will happily explain any term on their own estimate. Hesitation or irritation when you ask what a line item means tells you something useful about how the rest of the job will go.

When you are ready to read a real bid line by line, see what a roofing estimate should include and red flags when hiring a roofer.

The Parts of a Roof, Explained