Seamless GRP fibreglass flat roofing for Inverness homes and commercial properties. The preferred specification for Highland conditions - frost-resistant, maintenance-free, 25-year system guarantee. Extensions, garages, bay windows, porches and commercial roofs.
GRP fibreglass is the flat roofing system we specify most frequently across Inverness and the surrounding Highland area. The reason is straightforward: Highland winters are hard on flat roofs. Freeze-thaw cycling, sustained low temperatures, and high moisture loading create conditions that quickly degrade felt and expose the limitations of single-ply membranes. GRP - glass reinforced polyester - is a composite material that forms a seamless, rigid surface with no joints, seams or overlaps for water to penetrate. A correctly installed GRP flat roof on an Inverness property carries a 25-year system guarantee and requires no maintenance beyond an annual clearance of debris from outlets.
Traditional felt flat roofing relies on overlapping layers bonded with hot bitumen. In Highland conditions, sustained below-zero temperatures cause bitumen to become brittle and crack, and thermal cycling across the freeze-thaw boundary causes repeated expansion and contraction that lifts laps and creates pathways for water ingress. The average felt flat roof on an Inverness extension lasts 8–12 years before requiring replacement. A GRP installation in comparable conditions carries a 25-year guarantee and typically lasts considerably longer - the material does not degrade through thermal cycling in the way that bitumen-based systems do.
GRP installation begins with removal of the existing roof covering and inspection of the deck - OSB3 structural decking is specified for all GRP installations and we replace any compromised boarding before laying the system. The fibreglass laminate is applied wet, in layers, and allowed to cure to form a continuous rigid surface. Upstands are formed at all junctions and penetrations, and the surface is finished with a topcoat. The whole process on a standard extension roof takes one to two days. The roof is fully waterproof before we leave site.
GRP flat roofing costs more than felt per square metre but significantly less over its lifetime. On a standard single-storey extension in Inverness, the installed cost of a GRP flat roof runs from £800–£1,800 depending on area and access complexity. Bay windows and porches: £400–£800. Garage roofs: £1,200–£2,500 depending on size. All prices include deck inspection and replacement of any compromised boarding. We provide itemised quotes so you understand exactly what is included.
| Bay window or porch GRP roof | £400–£800 |
| Single-storey extension (up to 15m²) | £800–£1,400 |
| Single-storey extension (15–30m²) | £1,400–£2,200 |
| Garage GRP roof (standard single) | £1,200–£1,800 |
| Garage GRP roof (double) | £1,800–£2,800 |
| Commercial flat roof (per m²) | £45–£75/m² |
Free survey and written quote - no obligation. Call today.
Call 01463 262835"Extension roof in Merkinch - had felt replaced with GRP. Installed in a day and a half. Dry ever since and that was three Highland winters ago. Worth every penny over the felt quote."
"Bay window had been leaking for two years. Two roofers patched it, third one recommended GRP. They stripped it, replaced the deck boarding, installed GRP in one day. No leaks since."
"Garage roof replacement. The GRP quote was higher than felt but they explained why it was the right specification for the north-facing exposure. Three years on - no problems, no maintenance."
Whatever the roofing question, the right starting point is a professional survey carried out by a roofer who knows Highland conditions and the local housing stock. A survey costs nothing when combined with any roofing project, and £95–£150 as a standalone assessment. The written condition report that follows gives you a clear picture of the current state of your roof, what needs to happen and in what sequence, and what the costs will be.
We have been carrying out roof surveys, repairs and replacements across Inverness and Highland since 2003. NFRC registered. £5m public liability insurance. 10-year workmanship guarantee on all work. Free, no-obligation surveys across the full Highland area. Call 01463 262835 to arrange a visit, or use the contact form on our homepage. We aim to confirm survey appointments within one working day.
For a free survey across Inverness and all of Highland, call 01463 262835. We attend survey appointments within 3–5 working days for non-emergency work. Written quotes are provided within 24 hours of the survey visit. We carry NFRC registration, £5m public liability insurance, and offer a 10-year workmanship guarantee on all roofing work. No call-out fees, no obligation to proceed. If you have read this guide and have a specific question about your property, call us directly — we are happy to advise before you commit to any work.
Related reading: How much does a new roof cost in Inverness? — our full cost guide covering all roof types, materials and common price drivers for Highland properties. Also useful: Nail sickness in Inverness — the complete guide, and How to choose a roofer in Inverness for homeowners navigating contractor selection for the first time. Call 01463 262835 for a free survey and direct advice on your property.
Yes - GRP is our preferred specification for Highland flat roofs. Its seamless installation and resistance to thermal cycling make it significantly more durable than felt in freeze-thaw conditions. We carry 25-year system guarantees on all GRP installations.
A correctly installed GRP flat roof carries a 25-year system guarantee. In practice, GRP installations regularly exceed 30 years with no maintenance beyond annual outlet clearance. This is significantly longer than felt (8–12 years) or single-ply membranes (15–20 years) in comparable Highland conditions.
GRP requires ambient temperatures above 5°C during installation and curing. In practice this limits cold installation to dry periods between October and April, though work can proceed year-round in suitable weather windows. We will not install GRP in conditions that compromise the cure - this is part of specifying the job correctly.
A typical single-storey extension GRP roof in Inverness costs £800–£2,200 depending on area and access. Bay windows and porches: £400–£800. Garage roofs: £1,200–£2,800. All prices include deck inspection and replacement of compromised boarding. We provide itemised written quotes.
GRP is a rigid composite laminate; EPDM is a flexible rubber membrane. Both are excellent flat roof specifications for Highland conditions. GRP is more durable and carries a longer guarantee; EPDM is faster to install and marginally cheaper. We specify GRP where long-term performance is the priority and EPDM where budget or installation complexity favours a membrane approach.
Yes - all GRP installations carry a 25-year system guarantee covering both materials and workmanship. This is transferable to new owners if the property is sold. The guarantee requires an annual inspection of outlets and upstands which we can carry out as part of a maintenance visit.
Overlaying GRP onto existing felt is not recommended and is not our practice. We strip the existing covering, inspect and replace compromised deck boarding, and install the GRP system onto a clean, dry substrate. This is the only way to provide a meaningful guarantee on the installation.
No call-out fees. No obligation. Expert advice from local Highland roofing specialists.
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