EPDM vs GRP vs Felt: Flat Roof Options Compared
EPDM rubber suits most Leeds flat roofs, at £95 to £165 per square metre with a typical 25 to 30 year life. GRP fibreglass runs £110 to £185 per square metre and gives a hard walkable finish. Torch-on felt is the cheapest at £80 to £135 per square metre and lasts nearer 15 to 20 years. Ranges reviewed September 2026.
Most people ask which flat roof material lasts longest. It is the wrong first question. Nearly every failed flat roof we lift in Leeds failed at a detail: a lap that was never bonded properly, an outlet set too high, an upstand that was two courses too short, or a deck laid dead level so water sat on it for three days after every shower. Get the fall, the deck and the edges right and all three materials do a decent job. Get them wrong and the best membrane on the market still leaks.
That said, the three coverings behave differently, and one of them will suit your roof better than the others.
How do EPDM, GRP and felt compare?
Typical Leeds market ranges, reviewed September 2026. Prices assume a new deck and normal access from a tower or the ground.
| EPDM rubber | GRP fibreglass | Torch-on felt | |
|---|---|---|---|
| Cost per square metre | £95 to £165 | £110 to £185 | £80 to £135 |
| Typical life | 25 to 30 years | 20 to 30 years | 15 to 20 years |
| Joints on a small roof | None, single sheet | None, laid wet | Two or three lapped layers |
| Fitted in cold or damp | Yes | No, needs dry and above 5 degrees | Yes |
| Foot traffic | Soft underfoot, use a walkway | Hard, walkable | Moderate |
| Repairable | Yes, patched and bonded | Yes, ground back and re-laminated | Yes, heat welded patch |
| Weak point | Poorly bonded laps at upstands | Crazing where the deck moves | Blisters and split seams |
The figures above match the cost rows on our flat roofing page. A typical garage or dormer roof of around 12 square metres, stripped, re-decked and recovered, lands between £1,150 and £2,400.
When does EPDM make sense?
EPDM is a single sheet of synthetic rubber, bonded down over a ply deck. On a dormer or a rear extension up to about 15 square metres, the whole roof is often one piece with no joints anywhere in the field. Water has nothing to find.
It stays flexible in cold weather and copes with the deck moving slightly through the year, which matters on a timber extension. It can be laid on a damp winter day, so it suits emergency work when a felt roof has finally let go in November. The trade off is that the surface is soft. Someone walking on it in work boots with a bit of grit underfoot will mark it, so if the roof gets used for access to a Velux or an aerial, we lay a walkway.
For the flat-roofed rear extensions and dormers you see all over Pudsey and Farsley, EPDM is usually what we recommend.
When is GRP the better choice?
GRP is glass fibre matting laid into resin on a new ply deck, then topcoated. It cures into one hard shell with integral trims at the edges. Where a flat roof is also a balcony, a terrace or a walk-on area outside a loft conversion, GRP earns its price. You can put furniture on it. It takes a non-slip finish.
The catch is the weather. GRP has to go down dry and above about 5 degrees, so in Leeds that realistically means April to October, and it means a tent if the forecast turns. It is also unforgiving of movement. On a deck that flexes, GRP can craze into fine hairline cracks over time. A properly built deck with the right board thickness and noggins solves that, and a thin deck over widely spaced joists will show it up within a few winters.
Is torch-on felt ever the right call?
Yes, in two situations. On a large commercial or garage roof where the budget is fixed and the building has a limited future, a three layer torch-on system is honest value. And on a roof that already has a sound felt build-up with one failed area, a heat welded patch or a cap sheet overlay is a sensible repair at £220 to £650 rather than a full strip.
Modern polymer modified felt is a long way from the bitumen roofs that gave felt its reputation. It still has more joints than the other two, and joints are where flat roofs fail. It is also a naked flame on a timber roof, which we will not do close to a thatched or timber clad detail.
Does a new flat roof need Building Regulations approval?
Usually yes. Replacing the covering on a flat roof is listed on GOV.UK as work that needs building regulations approval, and where more than half the roof surface is being recovered it is treated as renovation of a thermal element. In practice that means the finished roof has to reach a set standard of insulation, which is set out in Approved Document L.
On a cold deck roof with a shallow void, that normally means converting it to a warm deck: insulation board over the deck, membrane over the insulation. Budget £30 to £60 per square metre for the upgrade. Leeds City Council building control can sign the work off, and so can an approved inspector. A patch repair to an existing roof does not trigger any of this.
It matters at resale. If the flat roof went on in the last few years with no building control sign off, a buyer’s solicitor will ask, and the answer costs you time at exactly the wrong moment.
What should a flat roof quote include?
- The deck: is it being replaced, and in what board and what thickness?
- The fall: what fall is being created, and how? Tapered firrings are the usual answer.
- The outlet: where does the water leave, and is the outlet being reset to the low point?
- Insulation: is the roof going warm deck, and to what U-value?
- The membrane: named product, single piece or lapped, and how the upstands are terminated.
- The edges: drip trims, gutter edge, and how the membrane meets the wall above.
- Building control: who notifies, and who gets you the completion certificate.
- The guarantee: workmanship term in writing, and any separate product guarantee.
If a quote gives you a price per square metre and nothing else, you have no way of knowing whether you are buying a roof or a covering laid over an old problem.
Working out which one fits your roof
The right answer depends on the deck, the fall, the access and what the roof has to put up with. We survey it, photograph what is under the existing covering where we can, and put the options in writing with a price against each. See our flat roofing page for how the job runs, or the Pudsey page if that is where your property sits.