GRP fibreglass, EPDM rubber and felt flat roofing for extensions, garages and outbuildings across Chichester. Coastal-rated systems with proper drainage — and a 10-year workmanship guarantee.
Flat roofing in Chichester uses GRP fibreglass and EPDM rubber for extensions and garages, costing £900–£5,500 depending on area. Both significantly outlast felt in the coastal climate and carry 20-year warranties. Free survey, no call-out fee. Call 01243 278085. Covering extensions and garages across Chichester and West Sussex.
Flat roofs are common across Chichester's housing stock — rear extensions on Victorian terraces in St Pancras and Whyke, detached garages on 1930s Summersdale properties, and the single-storey additions that are widespread on Portfield and Donnington post-war homes. Most of these flat roofs were originally laid in traditional mineral felt, and many are now reaching end of design life.
In Chichester's coastal climate, felt roofs deteriorate faster than they would inland. UV exposure and salt-laden air from the harbour cause the top layer to blister and crack, while ponding water accelerates the process. When we replace a Chichester flat roof, we recommend GRP fibreglass or EPDM rubber as the primary systems — both are proven in coastal environments and carry far longer design lives than felt.
All flat roof installations include proper fall specification, edge trims, outlet and drainage details, and upstand work where the flat roof meets a wall or parapet. These details are critical in Chichester where ponding water in a coastal climate accelerates failure.
Felt replacement (standard extension): £800–£2,000 · GRP fibreglass (extension): £1,500–£3,500 · EPDM rubber (garage): £1,200–£3,000 · Prices vary with size and access. Free survey and quote on all jobs.
Need a roofer in Chichester? Call us now — free quotes, no call-out fee
01243 278085"Had a GRP roof put on our rear extension to replace old felt that was leaking. The finish is excellent — completely seamless — and they explained every step of the process. No issues since."
"Our garage felt roof was blistering and pooling. They replaced it with EPDM rubber — it's been two years and it looks exactly as it did on day one. Great job."
"Straightforward felt replacement on our outhouse in Bosham. Competitive quote, turned up when arranged, clean job. Would recommend without hesitation."
The combination of coastal UV intensity, salt aerosol from Chichester Harbour and the persistent moisture from the Solent creates an environment where flat roofing materials — particularly traditional mineral felt — deteriorate measurably faster than in inland locations. UV radiation on the West Sussex coast is higher than at equivalent latitudes further north. Salt aerosol from the harbour deposits on flat roof surfaces, attacking the protective surface coating of felt and degrading the surface of EPDM membranes at a faster rate than in salt-free air. Properties within half a mile of the harbour — in Fishbourne, Bosham, Emsworth, Pagham — see flat roof failure at 8 to 10 years where equivalent inland properties might get 12 to 15 years from the same felt specification.
GRP (glass reinforced plastic) fibreglass is our primary flat roofing recommendation for Chichester properties. The material is applied as a liquid, cures to a rigid seamless surface and is finished with a UV-stable coloured gelcoat — typically light grey or slate grey. The seamless nature of GRP eliminates the jointing that is the primary failure mode of felt systems: there are no lapped joints to open, no weld seams to fail and no mechanical fixings to corrode. The gelcoat provides UV protection that outlasts the surface treatment on felt systems by a factor of 3 to 4 in Chichester's coastal UV environment. GRP can be applied over most existing deck substrates after appropriate preparation, making it a straightforward upgrade from a failing felt system. We back all GRP installations with a 20-year material guarantee from the manufacturer in addition to our 10-year workmanship guarantee.
Free survey — no call-out fee — Chichester & West Sussex
📞 01243 278085EPDM (ethylene propylene diene monomer) rubber is the appropriate flat roof system for larger areas where GRP's rigid nature makes installation more challenging — garage roofs over 40 square metres, large rear extensions, and any application where significant structural movement is anticipated. EPDM is installed as a single-ply membrane in very large sheet sizes — often in a single sheet for a standard garage — with minimal jointing. Its flexibility means it handles building movement without cracking. The material is resistant to UV radiation and ozone, and its design life of 30 to 50 years is comparable to GRP in Chichester's conditions. EPDM has a textured non-reflective finish that some homeowners prefer to the high-gloss GRP surface on visible rear extension roofs.
The single most important factor in flat roof longevity — more important than the membrane material — is correct drainage. A flat roof should not be flat: it needs a minimum fall of 1:40 (about 1.5 degrees) towards the outlet or gutter. A roof installed without adequate falls pools water at the low point, creating a constant wet environment that ages any membrane system faster and creates the freeze-thaw cycling in winter that opens joints and splits surfaces. We assess the existing falls on every flat roof survey and correct any drainage deficiency as part of the installation. On a re-covering job where the existing deck has inadequate falls, we use tapered insulation boards or re-deck with the correct fall built in. This adds modest cost but multiplies the system lifespan.
Replacing an existing flat roof like-for-like on a house extension or outbuilding is generally permitted development in Chichester — no planning permission required. Changing the material is also generally permitted where the visual impact is minimal. For listed buildings and properties in conservation areas, any alteration requires consent — and the material specification for conservation area flat roofs must be appropriate to the building. We advise on the planning position at the survey and will flag any consent requirement before work is committed to. If you are considering a new flat-roofed structure rather than re-covering an existing one, different rules apply and we can advise on whether the proposed structure is likely to require permission.
When a flat roof is being replaced — whether from failed felt to GRP or from an old EPDM system — it is the best opportunity you will have to upgrade the insulation without significant additional disruption. A flat roof extension that was built in the 1970s or 1980s almost certainly has inadequate insulation by current standards, and the heat loss through a poorly insulated flat roof is significant. When we strip back the existing covering, the insulation layer is fully accessible. Adding 80 to 150mm of high-performance PIR insulation boards at this point — combined into the reroof specification — improves the thermal performance of the roof by a factor of 3 to 4 over the original and reduces heating costs noticeably in the rooms below. We include an insulation assessment in all flat roof surveys and quote the insulation upgrade as an optional add-on so you can make an informed decision.
GRP and EPDM flat roofing systems carry manufacturer warranties ranging from 10 to 25 years depending on the product and the installer. These warranties cover material defects — delamination, surface degradation, manufacturing faults — but not installation errors, damage from foot traffic, or blockage of outlets causing ponding. Our 10-year workmanship guarantee runs alongside the manufacturer warranty and covers installation defects. In practice, a correctly installed GRP or EPDM flat roof in Chichester should not generate a warranty claim within its design life. The most common cause of early flat roof failure is incorrect installation — inadequate falls, poor edge detailing, unsupported upstands — rather than material failure. We carry out quality checks during installation and inspect the finished surface and drainage before leaving the site.
A typical rear extension flat roof in Chichester costs £800–£2,500 for a felt replacement, £1,500–£3,500 for GRP fibreglass, and £1,800–£4,000 for EPDM rubber depending on size and access. Garage roofs: £600–£2,000. Free quotes on all jobs.
GRP fibreglass and EPDM rubber both outperform traditional felt in coastal conditions. They resist UV degradation and the salt-laden air that accelerates felt failure. For most Chichester extensions and garages, we recommend GRP as the primary system — it carries a 25-year design life with minimal maintenance.
Traditional felt: 10–15 years before replacement. GRP fibreglass: 25+ years with proper drainage. EPDM rubber: 30+ years. Coastal conditions can reduce these slightly if the roof isn't maintained — we recommend an annual inspection to clear debris and check drainage outlets.
Both. We patch blistered or cracked felt sections, seal ponding areas and repair GRP roof damage. If more than 30% of the flat roof area is compromised, full replacement is usually more economical. We'll survey and advise honestly.
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 Chichester'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 Chichester. 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.
No call-out fees. No obligation. Just an honest quote from a local Chichester roofer who turns up when they say they will.
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