How to Read a Roofing Estimate (and Catch Hidden Costs)
By Roofing Price Tool Editors · Updated · 6 min read
The line items every honest estimate must include, the ones shady contractors leave off, and the per-sheet decking question that prevents four-figure surprises.
What a real estimate must list
An estimate that says "Roof replacement - $18,400" is not an estimate, it's a guess. A real estimate (following NRCA conventions) has line items so you can compare contractors apples-to-apples and so the work is contractually defined. Look for these eight items.
1. Material brand, line, and color
Not "30-year shingles." The brand (GAF, Owens Corning, Malarkey, Certainteed, IKO), the specific product line, and the color. Generic "comparable" language lets the contractor swap in cheaper stock without you noticing.
2. Underlayment type
Synthetic underlayment (Tyvek-style) vs felt (#15 or #30 paper). Synthetic is the modern standard. If the estimate says "felt" or nothing at all, ask why.
3. Ice & water shield coverage
Self-adhering membrane that goes at eaves, in valleys, and around penetrations. Code typically requires 3 feet up from the eave; some regions require 6. The estimate should state where it's installed.
4. Flashing
New flashing at chimneys, sidewalls, and valleys - not reused from the old roof. Reused flashing is the #1 source of post-install leaks. Ask explicitly: "Is all flashing new?"
5. Ventilation spec
Ridge vent, box vents, or powered vents - and intake at soffits. Code requires roughly 1 sq ft of net free vent area per 150 sq ft of attic, split between intake and exhaust. Mis-balanced ventilation voids most shingle warranties.
6. Tear-off and disposal
Removing the old roof, the dumpster rental, and dump fees should be included in the price - not added "if needed." A layover install (new roof on top of old) is a red flag.
7. Decking replacement allowance
This is the line item that creates 4-figure surprises. The estimate should state a per-sheet price for plywood replacement if rot is found (typically $50 - $100 per sheet) and an allowance for how many sheets are included. Without this, "we found rot - add $1,800" is a surprise at the worst possible moment.
8. Warranty terms
Both the manufacturer's warranty on materials (years, transferable or not, prorated or not) and the contractor's workmanship warranty (typically 5 - 25 years on labor). The contractor warranty is only as good as the contractor still being in business.
Red flags
- Single price, no breakdown. You can't compare bids and you can't dispute work.
- "Storm chaser" same-day quote. Real estimates take an inspection plus measurement, not 10 minutes in your driveway.
- Pressure to sign today. Real quotes are good for 30+ days.
- Large upfront payment. Standard is 30 - 50% on material delivery, balance on completion. Anyone wanting 100% upfront is risk you don't need.
- Cash-only discount. Unlicensed, unreported, no recourse if it leaks.
- Verbal change orders. Anything not in writing isn't real.
The three-quote rule
Get three written estimates from licensed contractors. Throw out the highest and the lowest. The middle one is almost always the right ballpark. If two bids are close and the third is far off in either direction, the outlier is wrong.
Before you collect any quote, know what the range should be. Run the calculator for your roof - when bids come in, you'll know which to trust.
Sources: NRCA · Better Business Bureau