Flat Roof Membrane Calculator — ft to rolls, adhesive, cost
How to use this calculator
Enter flat roof dimensions in feet and inches — length × width or direct area. Choose membrane type (EPDM, TPO, PVC, or modified bitumen), roll width, and seam overlap. The calculator estimates rolls needed, adhesive/bonding material, perimeter edge detail, and optional insulation boards.
Membrane types — EPDM (rubber, fully adhered or ballasted), TPO (heat-welded seams), PVC (heat-welded, chemical resistant), Modified bitumen (torch or cold-applied).
Overlap — Typical seam overlap is 3–6″ depending on membrane type and manufacturer specs.
Saved Calculations
| Time | Type | Area ft² | Rolls | Adhesive | Edge | Total $ |
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How to Calculate Flat Roof Membrane
This calculator estimates the number of membrane rolls, adhesive pails, edge metal pieces, and mechanical fasteners for flat or low-slope roofs. Supported membrane types include EPDM rubber, TPO, PVC, and modified bitumen. Enter roof dimensions in feet and inches, choose roll width (5 ft or 10 ft) and length (50 ft or 100 ft), set seam overlap, and get instant results.
Formulas
Effective roll coverage = (roll width − overlap) × roll length. Rolls needed = ⌈(roof area × (1 + waste%)) / effective coverage⌉. Adhesive = area / 100 ft² per gallon (fully adhered), rounded up to 5-gal pails. Fasteners ≈ 1 per ft² of membrane for mechanically attached systems.
FAQ
EPDM vs TPO vs PVC? EPDM is rubber-based, flexible, and economical. TPO is heat-welded with energy-efficient white surface. PVC is the most chemical-resistant, ideal for restaurants and industrial. Modified bitumen is traditional multi-ply.
How much adhesive? Fully adhered systems use ~1 gallon per 100 ft². Mechanically fastened systems use less adhesive but more fasteners.
