Flat Roof Costs 2026
Flat roofing has evolved. From the traditional 3-layer felt to seamless rubber and fibreglass systems, choosing the right material for your extension or garage depends on longevity, durability, and budget.
Bitumen Felt
The budget option. Modern torch-on felt is durable but has the shortest lifespan.
EPDM Rubber
The best all-rounder. 50-year lifespan, seamless, and highly resistant to UV damage.
GRP Fibreglass
The premium choice. Hard-wearing, ideal for balconies, and completely seamless.
Warm Roof vs Cold Roof
Warm Roof (Recommended)
Insulation is on top of the deck. No condensation risk, better energy efficiency, and easier to install to 2026 standards.
Cold Roof (Traditional)
Insulation between joists. Requires a 50mm ventilation gap to prevent 'interstitial condensation' and timber rot.
If you replace more than 50% of your flat roof, you are legally required to upgrade the insulation to achieve a U-value of 0.18 W/m²K.
Don't ignore "Ponding" water
If water stands on your roof for more than 48 hours, it's called ponding. This adds significant weight and can degrade even the best membranes over time. We recommend using firring strips during installation to create a 1:80 fall, ensuring water runs off into your gutters.
50-Year Potential
EPDM is biologically inert and resistant to ozone and UV, meaning it won't crack or rot.
Seamless Finish
GRP and large EPDM sheets eliminate joints, which are the #1 cause of roof leaks.
Quick Installation
Most domestic flat roofs can be completed in 1-2 days, minimizing disruption.
Flat Roofing FAQ
Calculate Your Flat Roof
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