EPDM vs GRP vs Felt: Which Flat Roof Is Best for Your Extension?

Flat roofs have improved enormously in the last twenty years. If you are building an extension or replacing a leaking garage roof, these are the three systems worth considering.

EPDM rubber

A single sheet of synthetic rubber with no seams on most domestic roofs. It handles London's freeze-thaw cycles well and can last 40+ years. The finish is a plain matt black.

• Lifespan: 40–50 years
• Very few joints to fail
• Quick to install, usually one day

Choose the system for how the roof will be used, not just the price per square metre.

GRP fibreglass

Laid as a liquid resin over a deck, giving a seamless, hard-wearing surface that can take light foot traffic. A good choice for roofs with lots of detail, or for balconies.

• Lifespan: 25–35 years
• Seamless and walkable
• Colour options available

Torch-on felt

Modern three-layer felt systems are far better than the old single-layer roofs that gave felt a bad name. They are the most affordable option and easy to repair.

• Lifespan: 20–30 years
• Lowest upfront cost
• Mineral finish in several colours