Estimate flat roof felt roll count and cost from area, lap loss, and roll pricing assumptions.
Underlayment cost is roll-coverage math. Overlap loss changes effective coverage and roll count significantly.
Enter values and click Calculate to see roll count and cost.
Start with the area that actually needs felt coverage.
Use the felt/synthetic roll specification planned for this project.
Reduce nominal coverage to effective coverage after overlaps and practical losses.
Round up to whole rolls, then apply price-per-roll for estimate totals.
Recheck valleys, upstands, and edge detailing before procurement.
Lap loss, layers, upstands, and detail rules vary by product/system. Confirm exact install instructions before final procurement.
Most ordering mistakes happen when assumptions are mixed across units, pitch, and coverage rules. Using Flat Roof Felt Calculator early helps align scope, quantity, and labor planning before supplier pricing or installer scheduling. This reduces reorders, avoids under-counting, and improves quote consistency.
Start with verified dimensions, run conservative waste assumptions, then compare output against product data sheets and field conditions. For cross-checks, pair this page with Underlayment cost calculator and Flat roof cost calculator.
Treat calculator output as a controlled estimate, then validate accessories, overlaps, and edge details separately. Final checks are stronger when you review assumptions with Single ply roofing cost calculator before submitting purchase orders.
It is designed for felt roll coverage planning and cost estimation. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions. Recheck dimensions, product coverage, and install requirements before purchase.
Overlap and lap losses reduce effective coverage per roll. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions. Recheck dimensions, product coverage, and install requirements before purchase.
Yes, include practical waste and detail allowances in addition to lap loss where needed. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.
Not exactly. Overlaps, end laps, and upstands reduce effective coverage, so real installed area per roll is lower than nominal label coverage. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.
Confirm sidelap and endlap requirements for your membrane system and local guidance before ordering. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.
Layer count depends on system specification and exposure needs. Follow product installation guidance and local requirements rather than generic one-layer assumptions. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.
Yes. Perimeter and penetration details consume additional material and must be included in final takeoffs. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.
No. Use it for planning quantities, then finalize with the selected membrane system specification and detail drawings. For better estimating accuracy, cross-check roll coverage, overlap width, and edge detailing with your project notes, then confirm drainage falls before final ordering. This keeps your system specification aligned with real site conditions and reduces costly quantity revisions.