Roof Leak Glossary: Roofing Terms Explained
Plain-English meanings for the roofing, insurance and permit words you'll hear when your roof leaks.
Written by the Valrico Roofing Pros team, 2700 St Anthony Dr, Valrico, FL 33594 · Updated October 31, 2026
Roofing terms explained in plain English: what flashing, underlayment, decking, valleys, pipe boots and the other words on your estimate actually mean, plus the Florida insurance and permit terms that come up with a leak. Each links to the page that covers it in detail. These are the words local roofers use every day in roof leak repair.
Roofing terms explained, A to Z
| Term | What it means |
|---|---|
| Assignment of benefits (AOB) | Signing your insurance claim rights over to a contractor. Banned for Florida policies issued since January 1, 2023. More |
| Actual cash value (ACV) | An insurance payout that subtracts depreciation for age and wear. Some Florida policies pay roof claims this way. More |
| Battens | Wood strips screwed down over a tarp's edges so wind can't get under it. More |
| Counter-flashing | Metal set into a wall or chimney that overlaps the step flashing below it. More |
| Cricket | A small peaked structure behind a chimney that sheds water around it instead of letting it pool. More |
| Decking | The plywood or OSB sheets nailed to the rafters that the roof is built on. Also called sheathing. More |
| Drip edge | Metal trim at the roof edge that directs water into the gutter and away from the fascia. More |
| Fascia | The board along the roof edge that the gutters attach to. More |
| Flashing | Thin metal that seals joints where the roof meets walls, chimneys, skylights, vents and valleys. More |
| Hurricane deductible | A separate deductible for named-storm damage, usually 2%, 5% or 10% of dwelling coverage. More |
| Hurricane straps | Metal connectors tying the roof framing to the walls, one of the features a wind mitigation inspection checks. More |
| Lift and relay | Lifting tiles off, replacing the underlayment beneath, and resetting the same tiles. More |
| Notice of Commencement | A document recorded with the county before work over $2,500 starts, under Florida Statute 713.13. More |
| Pipe boot | The rubber or metal collar that seals around a plumbing vent pipe where it comes through the roof. More |
| Ponding | Water that sits on a flat or low-slope roof after rain instead of draining. More |
| Ridge | The peak where two roof slopes meet at the top. |
| Roof-over | A new roof system built over an existing one, common on mobile homes. More |
| Soffit | The panel under the roof overhang, between the fascia and the wall, usually vented. More |
| Square | Roofing measurement: one square is 100 square feet of roof. More |
| Step flashing | L-shaped pieces of metal woven in with each course of shingles where a roof meets a wall. More |
| Underlayment | The waterproof layer under shingles or tiles. On tile roofs it's the real water barrier. More |
| Valley | The channel where two roof slopes meet and water runs off fastest. More |
| Wind mitigation inspection | An inspection recording hurricane-resistant features on Form OIR-B1-1802, used for insurance discounts. More |
| 25% rule | On pre-2007-code roofs, repairing more than 25% of a roof or section in 12 months can require the whole section to meet current code. More |
Why having roofing terms explained helps you
Knowing the words on an estimate helps you compare quotes. "Replace pipe boot and re-shingle 2 squares" is a very different job from "replace underlayment, 30 squares". If a roofer can't explain a line on your estimate in plain English, ask again. Still unsure? See the roof leak FAQ or the roof leak guides.
Glossary questions
What's the difference between flashing and underlayment?
Flashing seals joints where the roof meets something else. Underlayment is the waterproof layer under the whole roof covering.
What is a 'square' in roofing?
100 square feet of roof area. Roofers price and order materials by the square.
What part of the roof usually leaks?
Usually flashing, pipe boots, valleys and edges, not the middle of the roof. See roof leak detection.
Got a leak? The roofer will explain everything.
Call (813) 555-0147 or text us a photo of the stain. We’ll find where the water is getting in, show you photos, and explain the repair before any work starts.