EPDM Roof Calculator — Membrane, Adhesive & Trims
Calculate EPDM rubber membrane sizing with 75mm upstand allowance. Includes contact adhesive, perimeter trim and water check quantities.
Length of the flat roof
Width of the flat roof
Minimum 75mm per manufacturer spec
1.2mm is standard for domestic
How We Calculate This
This calculator sizes your EPDM membrane by adding upstand allowances to your roof dimensions, then calculates adhesive, trims and accessories.
The formula
Membrane size = (Roof length + 2 × Upstand) × (Roof width + 2 × Upstand)
Contact adhesive (L) = Membrane area ÷ Coverage rate (m\u00b2/L)
Perimeter trim = 2 × (Length + Width) + 10% extra
Frequently Asked Questions
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Last updated: March 2026
All calculations are estimates. Verify with your supplier.