GRP fibreglass, EPDM rubber and built-up felt flat roofing for extensions, garages and outbuildings across Chippenham and Wiltshire. Long-lasting solutions with proper drainage and free no-obligation quotes.
In short: Flat roofing in Chippenham costs £1,200–£2,500 for a GRP extension (25-year guarantee) or £900–£1,800 in EPDM. We strip, check the deck, correct the drainage falls and re-cover — the standard fix for the failed felt roofs common across Pewsham's extensions.
Flat roofs are only as good as their drainage and membrane. We install proper falls, correct edge detailing and modern membrane systems that last — not the quick fixes that are back leaking in three years.
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GRP Fibreglass Roofing
The most durable flat roofing option for Chippenham extensions and garages. GRP is seamless, waterproof, and carries a 25-year material guarantee. Installed in one continuous laminate with no joins for water to find.
Single-ply EPDM membrane is ideal for large flat roof areas. Lightweight, UV stable and highly resistant to the temperature extremes of Wiltshire winters and summers. Properly bonded with no torching required.
Three-layer built-up felt is a reliable and cost-effective option for garages and outbuildings. We use high-performance mineral-capped felt with full torch-on application — not laid cold over old felt.
Most flat roof failures in Chippenham trace back to poor drainage — insufficient fall, blocked outlets, or raised upstands. We assess and correct drainage design as part of every installation.
Blistering, ponding, splits or failing upstands repaired correctly. We identify the source of failure before patching — saving you money on recurring temporary repairs.
Where a flat roof is beyond repair, full strip and replacement is more cost-effective long term. We remove all existing layers back to deck, replace any rotted decking boards, and install the appropriate modern membrane system.
A failing flat roof rarely needs patching over and over. Once felt is past its life, replacement in GRP or EPDM costs about the same and lasts three times as long.
Ponding water that sits for days after rain
Cracked, blistered or lifting felt
Damp appearing on the ceiling of a single-storey extension
A felt roof more than 15 years old
Green algae and a soft, spongy deck underfoot
When it is not the answer: If a GRP or EPDM roof is only a few years old and has a single localised split, a repair is the right call — we won't sell you a full replacement you don't need. Read the full guide.
Diagram: national roofing standards illustrated. Advice on your roof is given after a free survey.
Local Knowledge
Flat Roofing on Chippenham Properties
The highest concentration of flat roof work we do in Chippenham is on rear extensions — particularly on Pewsham properties from the 1990s and 2000s where the original felt flat roofs are now 20–30 years old. Ponding is the most common complaint, caused by insufficient fall designed into the original extension. We correct the drainage issue as part of the re-roofing rather than applying new membrane over the same drainage problem.
On older Chippenham properties — Victorian and Edwardian terraces where additions to the rear of the property have flat roofs — we often find torch-on felt applied over original mineral felt. Where the underlying deck is sound, we strip to deck, check for rot, and install GRP or EPDM over a new plywood deck where required.
Flat Roofing Costs in Chippenham
GRP fibreglass (up to 20m²): £1,200–£2,500. EPDM rubber (up to 20m²): £900–£1,800. Felt re-roof (up to 20m²): £600–£1,200. Larger areas are priced per m². All prices include strip, deck inspection, drainage assessment and installation. Free written quote before any work starts.
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Chippenham, Wiltshire SN15
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We remove the old covering and inspect the deck for rot — the step most quotes skip.
2. Correct the falls
We check and correct drainage falls so water runs off cleanly rather than ponding.
3. Written quote
A fixed price covering deck repairs, membrane and trims, agreed before work starts.
4. Install the membrane
GRP is laid wet and cures seamless; EPDM is bonded as one sheet. Trims and upstands dressed in.
5. Sign-off & guarantee
The finished roof carries a 25-year material guarantee (GRP) plus our workmanship cover.
Timescales
Typical Timescales
Job
Typical duration
Small extension (GRP, up to 15m²)
1–2 days
Standard extension (GRP)
2–3 days
Garage roof (EPDM)
1 day
Deck / board replacement
+half to full day
Larger / commercial flat roof
per assessment
GRP needs dry conditions to cure; we won't lay fibreglass in rain, so winter jobs are weather-scheduled.
Access
Scaffold, Skips & Street Access
Single-storey flat roofs are usually reached from a tower or ladder; scaffold is quoted for two-storey or awkward access. Scaffold is specified for: two-storey flat sections, parapet work, or where safe edge protection is needed - always itemised in your written quote, never a hidden extra, and we arrange it.
Terraced streets around Chippenham's town centre and the historic core have no side access, so materials and waste pass over the front and scaffold setup takes longer; the post-war estates at Hardenhuish, Stanley and Cocklebury have generous access. Pavement scaffold and skip permits go through Wiltshire Council; allow a few working days on streets like Foghamshire, The Causeway, St Mary Street, the lanes around the Buttercross where space is tight.
Pricing
Flat Roofing Prices in Chippenham
Job
Typical range
Notes
GRP small extension (up to 15m²)
£1,200–£1,800
25-year guarantee
GRP standard extension (15–25m²)
£1,800–£2,500
Seamless fibreglass
EPDM standard extension
£900–£1,800
Single bonded sheet
Garage roof (GRP or EPDM)
£800–£1,600
Per garage
Deck / board replacement
£150–£400
Where timber has gone soft
Larger / commercial flat roof
from £45/m²
Single-ply or GRP
What moves the price
System choice — GRP vs EPDM by roof size and shape
Deck condition — soft boards need replacing before covering
Drainage falls — correcting shallow Pewsham falls adds labour
Number and complexity of upstands, trims and outlets
Worked example: A 18m² felt-roofed rear extension on a Pewsham estate house, stripped, two soft boards replaced, falls corrected and re-covered in GRP: around £2,100 with a 25-year guarantee.
No deposit on jobs under £500. On larger flat roofs, no payment before materials are on site. VAT included. Payment on completion once tested and dry.
Covering SN14, SN15, SN11, SN13 and surrounding postcodes.
Guarantee
The Guarantee in Plain Terms
GRP carries a 25-year material guarantee and EPDM 20 years; our workmanship cover sits on top, and the deck and falls — which decide longevity — are guaranteed too.
Covered: workmanship for 10 years, in writing, transferable if you sell.
On top: manufacturer warranties on materials (terms vary by product).
Not covered: storm or impact damage - that is an insurance matter, and we will document it for your claim.
If a fault appears in covered work, we come back and put it right. No quibbling, no re-charge.
Good to know
Disruption, Mess & Weather
A day or two of work over a single room, minimal internal disruption; we clear the old felt and all waste on completion. You do not need to stay home for external work - we just need power and access agreed in advance.
EPDM can go on year-round; GRP needs a dry weather window. We temporary-weatherproof if rain interrupts a job. Chippenham sits in the Avon valley, open to the prevailing south-westerlies, so exposed elevations weather faster and riverside streets in Hartham and Monkton Park hold damp longer into autumn.
Customer Reviews
What Chippenham Homeowners Say
★★★★★
"Extension flat roof had been patched twice and still leaked. Went for GRP this time — it's been two winters now with absolutely no issues. The drainage correction they did at the same time has stopped the ponding we'd had since the extension was built."
Susan P. · Pewsham, Chippenham · GRP flat roof replacement on extension
★★★★★
"Garage roof was completely sodden — three layers of old felt with water between each. Stripped back to deck, replaced three boards and installed new three-layer torch-on felt. Solid job, fair price, cleaned up perfectly."
Alan D. · Hardenhuish, Chippenham · garage felt roof replacement
★★★★★
"Large L-shaped extension flat roof done in EPDM. Impressed by how neat the upstand detailing is — previous quotes hadn't even mentioned it. No issues after the first winter."
Nicky R. · Calne Road area, Chippenham · EPDM rubber roof on large extension
GRP fibreglass is our first recommendation for domestic extensions in Chippenham — it's seamless, durable, and carries a 25-year material guarantee. EPDM is ideal for larger areas. The right choice depends on your roof size, shape and budget — we'll advise in the free survey.
GRP fibreglass: 25–40 years. EPDM rubber: 20–30 years. Good quality felt: 15–20 years. The most common cause of early failure is poor drainage design rather than membrane failure — we correct drainage as standard on every installation.
Depends on the condition of the deck and existing membrane. Isolated blisters or splits on a relatively new felt roof can be patched effectively. Where the membrane is 20+ years old or the deck is wet, replacement is more cost-effective. We assess and give you an honest recommendation.
Standard flat roof replacement like-for-like doesn't need planning permission. If you're adding a new extension with a flat roof, permitted development rules apply. We'll advise during the survey.
GRP fibreglass carries a 25-year material guarantee and regularly exceeds 40 years in service when correctly installed. The critical factors are proper deck preparation, correct resin formulation for ambient temperature, and correct upstand detailing. Shortcuts in any of these reduce service life significantly.
In some cases yes — usually on extensions where head height allows. It requires a structural assessment and planning consideration in some cases. We can advise on feasibility during the free survey, though pitched conversion work involves a builder as well as a roofer.
GRP fibreglass is rigid, seamless once cured, and has excellent resistance to foot traffic and point loads — ideal for most domestic extensions. EPDM rubber is more flexible, better suited to very large or complex-shaped roofs where thermal movement is a factor. We recommend the right system for your specific roof geometry.
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No call-out fees. No obligation. Honest pricing from a local Chippenham roofer.
