The Selsey peninsula is one of the most demanding environments for flat roofing in the South. We install GRP fibreglass and EPDM rubber exclusively here — coastal UV and salt air make felt a false economy.
Flat roofing on the Selsey peninsula presents challenges that simply don't exist 10 miles inland. The combination of extreme UV exposure from the southern coastal position, salt-laden air arriving from three compass points, and the near-constant wind movement across the flat peninsula creates a working environment that is genuinely hostile to traditional felt flat roofing systems.
The bungalow stock that dominates Selsey's housing is extensively extended — rear additions, garage conversions, glazed link extensions and annexes are very common across the peninsula, and the vast majority of these additions have flat roofs. Most were originally laid in mineral felt, and the majority of those are now past end of design life. We replace Selsey flat roofs exclusively with GRP fibreglass or EPDM rubber — felt replacement is not something we recommend in this location as the lifespan differential makes it poor long-term value.
Why We Always Specify GRP or EPDM in Selsey
UV resistance: Selsey's south-facing coastal position means higher UV exposure than inland towns — felt degrades visibly within 5–8 years, GRP and EPDM show no degradation over 25+ years
Salt air: Salt aerosol attacks felt surfacing and accelerates the cracking that leads to water ingress — GRP and EPDM are inert to salt exposure
Wind uplift: Properly installed GRP has no seams that wind can find — its single-piece surface eliminates the primary failure point of felt overlay systems
Ponding tolerance: Both GRP and EPDM handle standing water far better than felt — important on flat peninsula roofs where drainage outlets can be overwhelmed by coastal rain
Flat Roof Costs in Selsey
GRP fibreglass (extension): £1,500–£3,500 · EPDM rubber (garage): £1,200–£3,000 · Felt replacement (not recommended, available on request): £800–£2,000 · Free quotes on all jobs.
Need a roofer in Selsey? Free quotes — no call-out fee
"GRP flat roof on our bungalow rear extension in East Beach — replacing 1970s felt that had failed in three places. The GRP is perfect, completely seamless, no issues in two full winter seasons."
Lionel S. · East Beach, Selsey
★★★★★
"EPDM on our double garage roof — they explained the coastal specification clearly and why felt wasn't the right choice here. The system they installed looks and performs exactly as they described."
Pauline R. · Selsey Bill area
★★★★★
"Full flat roof inspection followed by GRP replacement on our link extension. Very thorough survey, clear quote, no surprises on the day. Best roofing experience we've had."
Kenneth W. · West Sands, Selsey
Why Selsey Specifically
Selsey bill is the most southerly point of west sussex and the most exposed location in our entire coverage area — three sides of the peninsula face open sea and the wind loading here is exceptional. For flat roofing in Selsey this means we carry out more post-storm emergency call-outs per property in Selsey than anywhere else we cover — the combination of low pitch, aging fixings and severe wind exposure creates a consistently high-risk profile. The town is predominantly bungalow and low-pitch residential from the 1950s onwards, with a significant number of properties that have had repeated storm damage from south-westerly gales. Full mechanical fixing throughout — tiles, ridge and hip — is our standard recommendation for any selsey re-roof, not just the exposed elevations.
EPDM vs GRP on Selsey Flat Roofs
On Selsey's exposed coastal position, the UV intensity and salt aerosol make the choice of flat roof system more consequential than on sheltered inland sites. GRP fibreglass performs well but requires careful installation — the gelcoat must be mixed and applied within the correct temperature range, which is not always achievable on exposed coastal sites in cooler weather. EPDM rubber has no temperature-sensitivity constraints during installation and its single-ply membrane has excellent resistance to UV and ozone degradation. For Selsey flat roofs, EPDM is our preferred specification where the installation conditions are uncertain.
Honest advice
How to Tell You Need Flat Roofing
Flat roof problems in Chichester almost always come down to a failed felt covering at the end of its 8–12 year life — ponding, splits, or blistering on an extension or garage roof.
Water pooling on the roof more than 48 hours after rain
Blisters, splits or cracks in an old felt surface
A damp patch on the ceiling directly below a flat roof
Felt lifting at the edges or around the upstand
A flat roof over 10 years old that has never been replaced
When it is not the answer: If the covering is a modern GRP or EPDM system only a few years old and the failure is a single localised split, a patch repair may be all it needs — not a full replacement. Read the full guide.
Warm deck vs cold deck flat roof constructionThe process
What to Expect: Flat Roofing in Selsey
1. Free survey
We assess the deck condition, the falls, and whether the failure is localised or end-of-life across the whole roof.
2. Written itemised quote
A quote covering deck repair if needed, the chosen system, and all edge detailing and upstands — itemised.
3. Scheduling
We book dry conditions for GRP work; EPDM has more flexibility on timing.
4. Strip and prepare
We strip the failed covering, repair or replace the deck, and correct the falls to the outlet.
5. System installation
We install the GRP or EPDM system with correctly formed upstands, trims and outlets — where flat roofs actually fail.
6. Cleanup and sign-off
Site cleared, final check, and the written guarantee plus 20-year system warranty handed over.
Timescales
Typical Timescales
Job
Typical duration
Garage flat roof
1 day
Extension flat roof (up to 25m²)
1–2 days
Larger EPDM area
2–3 days
Deck replacement (add-on)
+1 day
Dormer flat top
Half a day
GRP needs dry conditions above 5°C to cure correctly, so we plan fibreglass work around the forecast; EPDM is more weather-tolerant on exposed coastal sites.
Access
Access, Scaffolding & Permits in Selsey
Most flat roofs are single-storey extensions or garages reached from a tower or short scaffold; scaffold is quoted where the roof is at height or edge protection is needed. Scaffold is specified for: first-floor and higher flat roofs, or any flat roof where edge protection is required for safe working - always itemised in your written quote, never a hidden extra, and we arrange it.
Selsey's bungalow and chalet stock on the Manhood Peninsula gives easy low-level access, but maximum wind exposure demands secure fixing. Pavement scaffold and skip permits go through Chichester District Council; allow a few working days on streets like High Street, Hillfield Road, Beach Road where space is tight.
Pricing
Flat Roofing Prices in Selsey
Job
Typical range
Notes
Garage flat roof (GRP)
£900–£1,800
Seamless fibreglass
Extension flat roof (GRP)
£1,800–£4,000
Up to 25m²
Larger area (EPDM)
£3,500–£5,500
Single-ply rubber
GRP (per m²)
£80–£120
Supplied & fitted
Deck replacement
£25–£45/m²
If existing deck failed
What moves the price
Roof area and the chosen system (GRP vs EPDM)
Deck condition once the old covering is stripped
Number of upstands, outlets and edge details
Access height and edge protection
Whether falls need correcting to clear ponding
Worked example: A failed felt garage roof in Portfield stripped and refitted in GRP with new decking: around £1,450 including waste.
No deposit on flat roofs under £5,000. Payment on completion and inspection. No payment before materials are on site.
Covering PO20 and surrounding postcodes.
Guarantee
What the 10-Year Guarantee Actually Covers
The installation carries our written 10-year workmanship guarantee, with a 20-year manufacturer warranty on the GRP or EPDM membrane on top.
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 flat roof job is low-disruption — usually one to two days, single storey, minimal noise, and no need to be home for external work. You do not need to stay home for external work - we just need power and access agreed in advance.
EPDM installs in most conditions; GRP waits for a dry window. If rain interrupts, the deck is sheeted and protected until we can resume. Selsey Bill takes three-sided sea exposure — the most storm-battered position in the district.
FAQ
Frequently Asked Questions
A standard bungalow extension flat roof replacement in Selsey costs £1,000–£2,500 for EPDM rubber and £1,500–£3,500 for GRP fibreglass depending on size. We recommend GRP or EPDM over felt for all Selsey properties given the coastal exposure — felt lifespans are significantly reduced in this environment.
GRP fibreglass is our primary recommendation for the Selsey peninsula. Its seamless surface, UV resistance, and long design life (25+ years) makes it the most appropriate system for the extreme coastal exposure here. EPDM rubber is a close second for larger garage roofs. We do not recommend felt replacement as a long-term solution for Selsey — coastal UV and salt air reduce felt lifespan to 8–12 years at best.
Both. We patch and seal damaged GRP and EPDM sections, and repair felt blistering where the underlying structure is still sound. If more than 30% of the flat roof is affected, replacement is usually more cost-effective — we advise honestly after survey.
A standard bungalow extension flat roof replacement typically takes 1–2 days. Larger garage or multi-section roofs may take 2–3 days. We carry all materials to site and rarely need to source anything once work starts.
Blistering, cracking, pooling water after rain, or felt that has become soft and spongy to walk on are all signs a replacement is needed rather than a patch repair. If a felt flat roof is over 12 years old in Selsey's coastal climate and showing any of these signs, replacement with GRP or EPDM is almost always the more cost-effective long-term decision.
Replacing a flat roof like-for-like on a house extension or outbuilding is generally permitted development in Selsey. Changing the height or footprint, or work on a listed building or in a conservation area, may require consent. We advise at the survey stage.
Correct drainage is the single most important factor in flat roof longevity. All our flat roof installations include assessment of falls, outlet positioning and gutter connections before work starts. We correct any drainage deficiencies as part of the installation — a new flat roof laid to inadequate falls will fail early regardless of the material quality.
Survey and Specification for Selsey Flat Roofs
Every flat roof survey covers: the existing deck condition (whether the existing decking boards are sound or require replacement), the current falls (whether adequate drainage exists or whether tapered insulation is needed to correct the falls), the upstand heights (whether the covering can be taken up to the required minimum height at edges and abutments), and the outlet position and sizing. In Selsey, where the most exposed coastal location with three-sided sea exposure, we also assess whether coastal UV intensity or harbour moisture exposure affects the system recommendation. A flat roof that drains correctly and has proper upstand details lasts decades longer than one where these fundamentals were not addressed at installation.
GRP Installation Process
GRP fibreglass is applied as a liquid laminate that cures to a rigid seamless surface. We apply two layers of chopped strand mat saturated with resin, followed by the coloured gelcoat finish. The entire surface is seamless — no joints to open, no laps to fail. Upstands are formed to the correct height and radius at all edges. Outlets are GRP-lined. The gelcoat provides UV protection that significantly outlasts felt surface treatment in Chichester's coastal UV environment. Installation requires temperatures above 5°C — we plan flat roof work around weather forecasts to ensure the correct curing conditions.
Flat Roof Costs in Selsey
A standard single-car garage flat roof in GRP typically costs £900 to £1,800 in Selsey. Rear extension flat roofs up to 25m² cost £1,800 to £4,000. Larger areas of 25 to 60m² run £3,500 to £7,500. These prices include deck inspection, any necessary deck replacement, falls correction where needed, full GRP lamination and gelcoat finish. EPDM rubber costs approximately 10 to 15 per cent less than GRP on the same area with comparable performance over the long term.
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