Highworth's flat roof stock is concentrated on the post-war estates where 1970s–80s rear extensions added kitchen-diners and utility rooms under flat felt roofs. These are now 35–45 years old — well past the 15–20 year felt lifespan. The hilltop exposure compounds every failure mode: UV degradation is more intense at elevation, wind uplift stress on the membrane edges is higher, and the wider temperature swings cause more expansion-contraction cycling.
Highworth's flat roof stock is concentrated on the post-war estates where 1970s–80s rear extensions added kitchen-diners and utility rooms under flat felt roofs. These are now 35–45 years old — well past the 15–20 year felt lifespan. The hilltop exposure compounds every failure mode: UV degradation is more intense at elevation, wind uplift stress on the membrane edges is higher, and the wider temperature swings cause more expansion-contraction cycling.
Flat roof edges are the most vulnerable point for wind uplift. In Highworth's exposed position, the uplift force at the roof perimeter is significantly higher than in Swindon. We fit all flat roofs with mechanical edge trims screwed at 200mm centres rather than the standard 300mm, and use bonded GRP or fully adhered EPDM rather than loose-laid systems. This prevents the membrane lifting that causes so many flat roof failures in wind-exposed locations.
When we strip old felt flat roofs in Highworth, we consistently find chipboard decking that has swelled and delaminated from decades of moisture ingress. The hilltop humidity — less than Cricklade's river valley but higher than you'd expect for a hilltop — keeps the deck damp enough to deteriorate. We replace all chipboard with 18mm WBP marine-grade plywood, which handles moisture without structural compromise.
Proper falls matter everywhere, but at Highworth's elevation, standing water is subject to more freeze-thaw cycles than in sheltered locations. Ponded water freezes faster and stays frozen longer, expanding against the membrane and deck. We build minimum 1:40 falls using tapered firring strips, ensuring positive drainage to the outlet after every rainfall.
Flat roofs in Highworth face the same hilltop wind exposure as pitched roofs — but with less pitch to shed water and more surface area for wind uplift. The 1970s–80s rear extensions across Pentylands and Hampton used felt flat roofs that have long exceeded their design life. The exposed position means these roofs cycle through more extreme temperature ranges than in sheltered Swindon, cracking the membrane faster. GRP or EPDM replacement is the only lasting solution.
No call-out fees. Free quotes. 10-year guarantee. Call 0179 329 7084.
0179 329 7084"Our kitchen extension flat roof had been leaking for three winters. They stripped the old felt, replaced the chipboard deck, and laid GRP fibreglass with proper edge trims. First winter completely dry. The difference is remarkable — should have done it years ago."
"Garage roof was a mess — felt cracked everywhere. They recommended EPDM for the larger area, fitted it in a day, and it looks neat and professional. Twenty-year guarantee gives real peace of mind at this exposed location."
"The dormer window flat roof had been a problem since we bought the house. They stripped it, found rotten timber underneath, replaced two joists and the full deck, then laid GRP. Finally sorted after years of patching."
A porch or bay flat roof: £800–£1,500. A garage: £1,200–£2,500. A rear extension: £2,500–£5,000. Highworth specifications include enhanced edge fixings for wind exposure — this adds a small amount to the standard price but prevents the uplift failures we see on basic installations. Porch: £800–£1,500. Garage: £1,200–£2,500. Extension: £2,500–£5,000. GRP and EPDM both carry 25–30 year manufacturer guarantees. See our flat roof cost guide for detailed pricing.
GRP for smaller roofs and walkable surfaces — it's rigid, seamless and extremely durable. EPDM for larger areas like garages — it handles thermal movement better and can cover big areas in a single sheet. Both carry 20+ year guarantees. We recommend based on your specific roof. GRP is seamless, rigid and walkable. EPDM is flexible and better for larger areas. Both massively outperform traditional felt. BS 6229:2018 specifies minimum 1:40 falls. See our GRP vs EPDM comparison.
The exposed hilltop position creates wider daily temperature swings and more freeze-thaw cycles than sheltered locations. This expansion-contraction cycling cracks older felt membranes faster. Wind uplift stress on membrane edges is also higher here. Modern GRP and EPDM handle these conditions far better than old felt. We always strip to deck, inspect joists, and build correct falls. No overlaying. Warm deck insulation specified as standard per Building Regulations. See our warm vs cold deck guide.
If the membrane is intact with localised damage, a repair may work. If the felt is cracked, blistered or delaminating across the surface — which is the case on most 35+ year old Highworth flat roofs — replacement with GRP or EPDM is the only lasting fix. We always strip to deck, inspect joists, and build correct falls. No overlaying. Warm deck insulation specified as standard per Building Regulations. See our warm vs cold deck guide.
Always. We strip back to the deck and inspect every board. In Highworth, we find chipboard deck failure on about 70% of the flat roofs we replace. We always upgrade to marine-grade plywood — it costs slightly more but eliminates the deck rot that kills flat roofs from underneath. We always strip to deck, inspect joists, and build correct falls. No overlaying. Warm deck insulation specified as standard per Building Regulations. See our warm vs cold deck guide.
Most domestic flat roofs in Highworth are completed in 1–2 days. Larger or more complex roofs with deck replacement may take 2–3 days. We schedule around weather — particularly important at this exposed elevation. We always strip to deck, inspect joists, and build correct falls. No overlaying. Warm deck insulation specified as standard per Building Regulations. See our warm vs cold deck guide.
Yes — manufacturer-backed guarantees of 20–25 years on both GRP and EPDM, plus our 10-year workmanship guarantee. We always strip to deck, inspect joists, and build correct falls. No overlaying. Warm deck insulation specified as standard per Building Regulations. See our warm vs cold deck guide.
Highworth sits on an exposed limestone ridge at 120m above the Upper Thames vale. The hilltop position creates wind loading 20-30% higher than sheltered Swindon. Ridge and verge tiles are displaced more frequently here than anywhere else we cover. The 1970s-80s Pentylands and Hampton estates are entering peak re-roof demand as nail sickness reaches critical failure point on 50-year-old fixings.
We strip the old membrane completely, inspect the deck (replacing rotten chipboard with marine-grade plywood where needed), build proper falls using tapered firring strips to ensure positive drainage, install ventilation to prevent condensation, and lay the new GRP or EPDM membrane with mechanical edge trims and proper upstand detailing. Most domestic flat roofs are completed in 1-2 days.
We are NFRC registered, carry £5m public liability insurance, and provide a written 10-year workmanship guarantee on every job. We know Highworth's housing stock, its specific climate challenges, and the materials that work best in local conditions. We do not subcontract — our own team handles every job from survey to completion. Call 0179 329 7084 for a free quote.
We strip the existing membrane completely — we never overlay new material on top of old. We inspect every board of the deck, replacing any chipboard, OSB or plywood that shows moisture damage, delamination or structural weakness. All replacement decking is 18mm WBP marine-grade plywood. We build falls using tapered firring strips to achieve a minimum 1:40 gradient to the outlet — standing water is the number one killer of flat roofs and correct falls eliminate it. Edge trims are mechanically fixed at 200mm centres with stainless steel screws. Upstands are formed to a minimum 150mm above the finished roof surface. We install ventilation to prevent condensation in the void.
A well-installed GRP or EPDM flat roof needs minimal maintenance, but a few simple steps will maximise its lifespan. Keep the surface clear of debris — leaves, moss and dirt can block drainage outlets and cause ponding. Check the edges and upstands annually for any lifting or separation, particularly after winter. Inspect the outlet and ensure it is flowing freely after heavy rain. Do not place heavy items on the surface without load-spreading boards. Do not use a pressure washer on EPDM — it can damage the rubber surface. For GRP, avoid dragging furniture or ladders across the surface — the resin coat can be scratched. If you notice any damage, call us early — a small patch repair costs a fraction of the damage that water ingress will cause if left untreated.
Every specification we write for Highworth accounts for the hilltop wind exposure. Enhanced mechanical fixings on ridge and verge tiles, code 4 lead with additional dressing on west-facing flashings, and deep-profile guttering rated for the higher rainfall volume that wind-driven rain delivers at elevation.
From £150, no call-out fee.
More →Full re-roofs, 10yr guarantee.
More →GRP/EPDM, 25yr guarantees.
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Call Now →Cleaning, repairs, replacement.
More →Repointing, flashings, stacks.
More →Biocide, 3-5yr protection.
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More →Code 4 flashings, valleys.
More →Repair, matching, re-roofing.
More →Surveys from £120, fee credited.
More →Here is how to tell if this is the right service for your property.
When it is not the answer: If membrane is flexible, deck firm, and leak is from one point, a £200-£400 patch may give years more service.
Check membrane, deck, falls, upstands, outlet.
GRP and EPDM options, itemised.
Strip, new deck, firring strips for falls, membrane, trims, upstands.
10-year workmanship + 25-30yr manufacturer warranty.
| Job | Duration |
|---|---|
| Porch/bay | 1 day |
| Garage | 1-2 days |
| Extension | 2-3 days |
Weather dependent.
Ladder access for most. Scaffold for first-floor flat roofs.
Hilltop at 120m — fully exposed from all directions. Limestone properties require period-correct materials. Pavement scaffold and skip permits go through Swindon Borough Council; allow a few working days on streets like Sheep Street, High Street, Brewery Street.
Workmanship 10 years. System warranty 25-30 years.
2-3 days. GRP resin odour during cure — close windows below for a few hours.
GRP needs dry conditions and 5°C+. EPDM more tolerant. Elevated position produces 10-15% more frost days than Swindon town centre.
Last updated: August 2026
No call-out fees. No obligation. Local Highworth roofers you can trust.
0179 329 7084