Wondering what a flat roof costs in Farnham? Real 2026 prices for GRP, EPDM and felt, why drainage falls matter more than the membrane, and a worked local example. Free survey and honest material advice.
Flat roofing in Farnham costs £800–£6,000 depending on material and area. A single garage in EPDM is typically £1,600–£2,400; a small extension in GRP £2,400–£4,200. Correct drainage falls are included on every job. Free written quote — call 0125 244 7622.
Flat roofing in Farnham costs £800–£6,000 depending on the material and the area covered. Most domestic flat roofs — on extensions, garages, dormers and bay tops — are priced per square metre supply and fit: felt around £40–£70/m², EPDM rubber £80–£120/m², and GRP fibreglass £95–£140/m². For a typical single-garage or small extension roof of 15–30m², that translates to roughly £1,200–£3,500 for felt, £1,800–£3,200 for EPDM, and £2,400–£4,200 for GRP.
The material you choose is the biggest single variable, and it's a genuine long-term decision rather than just an upfront one. Felt is cheapest to install but lasts only 15–20 years. EPDM rubber lasts 30–50 years with very few seams and is the best all-rounder for garages and larger areas. GRP fibreglass cures into a completely seamless, hard-wearing surface, lasts 25–30 years, and is the right choice for balconies, bay tops and anywhere that will be walked on.
The most common cause of flat roof failure isn't the material — it's inadequate drainage. A flat roof laid without correct falls holds standing water, and no membrane survives permanent ponding. BS 6229 requires a minimum finished fall of 1:80 to ensure positive drainage. Many of the failed flat roofs we're called to inspect in Farnham were installed level or with reversed falls, so they pond and fail regardless of how good the membrane was. We re-profile the deck to correct the falls as part of any flat roof installation — it's not an optional extra.
A proper flat roof quote includes strip-off and disposal of the old covering, any deck repair needed, the new membrane, correct falls, all trims and edge detailing, and — where more than a quarter of the roof is being replaced — the Part L insulation upgrade that Building Regulations require. Strip-out and disposal alone adds £300–£700 to almost every job and is frequently left out of headline quotes, so always confirm it's included in writing.
Most flat roofing work in Farnham is on rear extensions and garages added to properties from the 1960s onwards. The post-war and 1970s–80s houses across Heath End, Badshot Lea and Weybourne almost universally have flat-roofed garages and single-storey additions, and a large proportion of these were originally felted. Felt laid in the 1980s is now decades past its service life — the flat roofs failing across these estates now are the original coverings reaching the end of the line, not recent installations gone wrong.
The 1930s semis in Wrecclesham and Rowledge often carry flat-roofed bay tops and small rear additions where lead and felt meet — junctions that need careful detailing and are a frequent source of leaks when the original work was done cheaply. And the wooded aspect of roads like The Bourne means flat roofs there collect leaf debris that blocks outlets and accelerates ponding, so drainage design matters even more.
One local practicality worth knowing: GRP fibreglass requires warm, dry conditions to cure properly — typically above 5°C and no rain. Through a Surrey winter, GRP installations often can't happen at all, which can push a job into spring. EPDM and felt are less weather-sensitive and can be laid in a wider range of conditions. If your flat roof fails in December, EPDM may be the more practical choice simply because it can be installed sooner.
A typical single-garage flat roof in Heath End, around 18m², with the original failed felt stripped and replaced in EPDM including new trims and a corrected fall, would usually land around £1,600–£2,400 in 2026. The same roof in GRP would be roughly £2,200–£3,000. Felt would be cheaper still upfront, but given it would need doing again in 15 years, EPDM is the better value over the life of the roof for most homeowners.
BS 6229:2018, the British Standard for flat roofs, requires a minimum finished fall of 1:80 to ensure positive drainage and prevent the ponding that is the leading cause of flat roof failure.Source: BS 6229:2018
| Material / Job | Typical Cost |
|---|---|
| Felt (per m² supplied & fitted) | £40–£70/m² |
| EPDM rubber (per m²) | £80–£120/m² |
| GRP fibreglass (per m²) | £95–£140/m² |
| Single garage (~18m²) — EPDM | £1,600–£2,400 |
| Small extension (15–30m²) — GRP | £2,400–£4,200 |
| Bay window roof | £450–£1,200 |
| Strip-off & disposal (add) | £300–£700 |
"GRP flat roof on our kitchen extension. They explained why the falls mattered and re-profiled the deck so it drains properly now. £2,600 all in — fair for the quality."
"Replaced the felt on our garage with EPDM. Quick, clean, and half the price of a couple of other quotes that were pushing GRP we didn't need. Good honest advice."
"Bay window flat roof was leaking into the front room. Sorted with new lead and a proper GRP top. They itemised everything. No hidden costs."
Flat roofing in Farnham costs £800–£6,000 depending on material and area. A single garage in EPDM is typically £1,600–£2,400; a small extension in GRP £2,400–£4,200. Prices are per square metre: felt £40–£70, EPDM £80–£120, GRP £95–£140.
GRP fibreglass is our standard recommendation for bay tops, balconies and walked-on roofs — seamless and hard-wearing. EPDM is the best all-rounder for garages and larger areas, lasting 30–50 years. Felt is cheapest but shortest-lived. We advise at survey stage.
The leading cause is inadequate drainage, not the material. A roof laid without correct falls holds standing water, and no membrane survives permanent ponding. We re-profile the deck to correct the falls on every flat roof installation.
Felt lasts 15–20 years, GRP 25–30, and EPDM 30–50. EPDM is usually the best value over the full lifespan despite a higher upfront cost than felt, because you avoid the replacement cycle.
EPDM and felt can be laid in a wide range of conditions, but GRP fibreglass needs warm, dry weather above about 5°C to cure. Through a Surrey winter, GRP jobs often have to wait for spring. If yours fails in cold weather, EPDM may be the practical choice.
Replacing more than a quarter of a flat roof triggers a Part L requirement to upgrade the insulation. Full replacements usually need Building Control notification. We handle this as part of the job and include it in the quote.
Yes. Stripping and disposing of the old covering adds £300–£700 to most jobs and is a real cost — we always include it in writing rather than adding it later. Always check any quote states this explicitly.
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