Garage Roof Replacement: Felt, GRP or Tiles — Which Is Right?

Flat Felt Garage Roofs

The majority of Aylesbury's garage flat roofs are built-up felt on timber deck — either flat or with a minimal pitch designed to shed water to one edge. These were standard construction from the 1950s through the 1990s and have a design life of 20–25 years. On properties built before 1990, the original felt is now at or past end of life.

Replacement options are GRP fibreglass (our default recommendation for most situations), EPDM rubber, or torch-on felt. GRP and EPDM significantly outperform torch-on felt for longevity — they carry 25-year warranties versus 10–15 years for quality torch-on systems. The key decision factor is deck condition: a rotten or saturated deck needs replacing regardless of which membrane system is chosen, and the deck replacement cost is the same across all systems.

Pitched Concrete Tile Garage Roofs

Single-garage pitched roofs with concrete interlocking tile are found across Bedgrove, Quarrendon, and the broader 1970s–80s estate housing. They share the same nail sickness timeline as the main house roof. Where the garage roof is connected to the main roof — sharing battens or a ridge — the nail sickness and felt condition typically mirror the house.

Re-roofing a detached garage in concrete tile costs significantly less than the main house — a typical single detached garage is 15–20m² compared with 55–70m² for the house. Budget £800–£1,800 for a standard concrete tile re-roof on a single garage, depending on access and tile specification. This is worth combining with the house re-roof if both are due — single scaffold access reduces overall cost.

Pitched Clay Tile Garage Roofs

Less common — typically found on older properties where the garage was built to match the original house specification. Clay plain tile garages in the conservation area or on period properties require like-for-like replacement matching the original profile. Cost is higher than concrete tile due to material cost, but the specification requirement is non-negotiable on conservation area and listed properties.

When to Repair vs Replace a Garage Roof

For flat felt roofs: if the membrane is under 15 years old and the failure is localised (one split seam, a failed outlet), targeted repair is appropriate. Over 20 years old, or where failures are widespread, replacement is the more economical choice over a 10-year horizon. Pitched tile roofs follow the same repair/replace logic as the main house — nail sickness extent and felt condition are the deciding factors.