Garage Flat Roof Replacement: A Complete UK Guide

Garage flat roof replacement is one of the most common roofing jobs we carry out. Most garages were originally covered with mineral felt, which has a lifespan of 10–20 years. When it fails, it's an opportunity to upgrade to a modern, long-lasting system.

Signs Your Garage Roof Needs Replacing

• Felt has cracked, split, or lifted at the edges
• Blistering across the surface
• Water staining inside the garage
• Moss and algae growth
• The felt is more than 15 years old

Which System Should You Choose?

For a typical domestic garage, GRP fibreglass is our most recommended option. It's extremely durable, seamless, looks great, and comes with a long guarantee. EPDM rubber is an excellent alternative — it's particularly good if the roof has an unusual shape or low pitch.

Typical Costs

A standard single garage (roughly 3m × 5m = 15m²) will typically cost £800–£1,500 for GRP fibreglass or EPDM, including removal and disposal of the old felt. A double garage will be proportionally more. Prices vary by region.

The Process

The old felt is stripped off. The deck is inspected and any rotten timber is replaced. New insulation may be added at this point. The new membrane is then installed. A typical single garage can be completed in one day.

Planning Permission

Replacing a flat roof on a garage does not normally require planning permission as long as you're replacing like-for-like. If you're significantly changing the structure or height, check with your local planning authority.