The three types of flat roof we lay in Brighton and Sussex are torch-on felt, EPDM rubber and GRP fibreglass. Each one works well on the right roof. Here is how they compare.
Torch-on felt
Modern felt is a reinforced bitumen membrane laid in two or three layers, each one heated with a torch to bond it, finished with a mineral cap sheet that protects it from the sun. It is tough, familiar and easy to repair, and suits garages, extensions and dormers. Expect 20 years or more from a well-laid system.
EPDM rubber
EPDM is a synthetic rubber membrane laid as one sheet, bonded to the deck, with no joints across the roof. It stays flexible in heat and cold, is laid without a flame and suits simple shapes. Expect 25 years or more.
GRP fibreglass
GRP is glass-reinforced resin laid on the roof in liquid form over a mat, then finished with a coloured topcoat. It gives a hard, jointless finish you can walk on, and handles awkward shapes, rooflights and balconies well. Expect 25 years or more.
GRP vs EPDM: which is better?
Neither wins on every roof. EPDM vs GRP comes down to shape and use: EPDM goes down as one flexible sheet, so it is quick and clean on a simple rectangle and copes well with movement. GRP is laid wet, so it wraps neatly round rooflights, upstands and awkward corners and gives a hard surface you can walk on. Both last 25 years or more when the deck underneath is sound.
Which one for your roof?
Felt for value and easy repair. EPDM for a clean, jointless finish on a simple roof. GRP for a hard-wearing surface, complex shapes or a roof you will walk on. The deck underneath matters as much as the covering, so we replace it every time.
What about the old roof?
We strip the old covering and the deck back to the joists, replace rotten timber, lay a new OSB deck and then lay the new system. Overlaying an old roof traps moisture and shortens the life of the new one.
Get a real price for your roof
Ranges are a guide. The real number comes from someone looking at your roof. William comes out, shows you what is needed and gives you a free written quote.
Questions
Which flat roof lasts longest?
EPDM and GRP both last 25 years or more when laid properly. Felt lasts 20 years or more. Workmanship and the deck matter more than the system.
Can you lay felt without a torch?
Yes. Cold-applied and self-adhesive felt systems exist for places where a flame is not suitable.
Which is cheapest?
Felt and EPDM are close on most roofs. GRP costs a little more. Our flat roof cost guide has 2026 ranges.