Bosham's quayside properties are some of the most atmospheric in the county — and some of the most demanding to roof correctly. The combination of conservation area restrictions, tidal moisture from Bosham Channel, and predominantly flint-built construction requires genuine specialist knowledge.
Bosham's quayside properties are some of the most atmospheric in the county — and some of the most demanding to roof correctly. The combination of conservation area restrictions, tidal moisture from Bosham Channel, and predominantly flint-built construction requires genuine specialist knowledge.
Flat Roofing Systems in Bosham
GRP fibreglass with marine-grade gelcoat is the recommended system for Bosham flat roofs. The tidal moisture and salt aerosol from Bosham Channel means EPDM is also appropriate for larger areas. Felt is completely unsuitable for quayside properties.
Garage Flat Roof
£900–£,600
Extension Flat Roof
£1,800–£5,200
Survey
Free
Guarantee
10 Years
Where We Fit Flat Roofs in Bosham
Flat roofing work in Bosham covers rear outbuildings and garage extensions on back-lane properties above the quayside. All flat roof work is surveyed before quoting — falls, drainage points, upstand details and any existing structural issues are assessed as part of the free survey.
Free quote — no call-out fee — Bosham and surrounding area
GRP fibreglass provides the longest lifespan and the most seamless finish; it is our default recommendation for most Bosham properties. EPDM rubber is cost-effective for larger areas and equally durable. Felt is not recommended for any Bosham property — the lifespan is too short to justify the cost, in Bosham's tidal harbour environment.
Customer Reviews
What Bosham Customers Say
★★★★★
"Garage flat roof was leaking after only twelve years on the old felt. GRP conversion — not a drop since. Should have done it years ago."
Seraphina R. · High Street, Bosham
★★★★★
"Extension flat roof done in GRP. Neat finish, no mess left. They explained every step of the process before starting."
Lysander F. · Old Bosham
★★★★★
"Had EPDM on the large back extension. Brilliant product, very professional installation. Highly recommend."
Bosham is tidal harbour village — the quayside properties are within metres of the water and the salt aerosol concentration here exceeds anything we measure elsewhere in the coverage area. For flat roofing in Bosham this means lead flashings on Bosham quayside properties oxidise visibly within 5 years without patination oil — the tidal exposure here is categorically different from harbour-adjacent properties a mile inland. The historic quayside cottages and victorian properties around the church are heritage stock requiring conservation-aware materials, while the residential streets further from the water are standard post-war and modern. Marine-spec lead work with patination oil is mandatory on all bosham harbour-edge properties — we do not offer it as optional on these sites.
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 Bosham
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 Bosham
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.
Bosham's waterside conservation village has narrow lanes, tidal-road access constraints, and listed properties needing conservation-correct work. Pavement scaffold and skip permits go through Chichester District Council; allow a few working days on streets like Bosham Lane, High Street, Shore Road where space is tight.
Pricing
Flat Roofing Prices in Bosham
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 PO18 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. Bosham's harbour setting brings the highest humidity and salt-driven lead oxidation in the area.
FAQ
Flat Roofing Bosham: Common Questions
GRP fibreglass with marine-grade gelcoat is the recommended system for Bosham flat roofs. The tidal moisture and salt aerosol from Bosham Channel means EPDM is also appropriate for larger areas. Felt is completely unsuitable for quayside properties.
A typical garage flat roof in Bosham costs £900–£,600. A rear extension flat roof is typically £1,800–£5,200 depending on size and system. We quote by the square metre after a free survey.
GRP fibreglass lasts 25 to 40 years in Bosham's conditions. EPDM rubber lasts 30 to 50 years. Traditional felt lasts 8 to 12 years at most in Bosham's tidal harbour environment — we do not recommend felt replacement for any Bosham property.
Yes — felt to GRP conversion is a standard job for us. We remove the existing felt and boarding, install new treated decking, apply the GRP system and finish with a UV-stable coloured gelcoat. The improvement in lifespan is significant and the upfront cost difference is recovered within a few years.
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 Bosham'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 Bosham. 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 Bosham 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 Bosham, where tidal harbour quayside properties with maximum salt aerosol, 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 Bosham
A standard single-car garage flat roof in GRP typically costs £900 to £1,800 in Bosham. 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.
Get In Touch
Free Quote — No Call-Out Fee
Honest pricing from a local Chichester roofer. Call now or request a quote online.
