GRP Fibreglass Roofing

GRP (Glass Reinforced Polyester) fibreglass is a cold-applied liquid system that cures to form a completely seamless, hard-wearing roof surface. It's the premium choice for walkable flat roofs like balconies and terraces.

What is GRP fibreglass roofing?

A two-part system applied cold directly to an OSB deck:

1. Resin and mat layer — chopped strand glass mat saturated with polyester resin, applied by hand
2. Topcoat — pigmented, UV-resistant, wear-resistant finish

The system cures chemically to form a fully-bonded, seamless surface with no joints or weak points.

Where GRP excels

• Walkable surfaces — balconies, terraces, roof gardens, step-out areas
• Complex shapes — valleys, upstands, intricate details
• Premium installations — when you want the best finish possible
• Colour matching — topcoat available in any RAL colour

Where GRP isn't ideal

• Large simple roofs where EPDM is more cost-effective
• Garages and outbuildings where budget matters more than finish

Installation process

1. Strip existing roof covering
2. Inspect and repair deck — must be 18mm OSB or plywood in good condition
3. Install insulation if needed (warm roof construction)
4. Apply resin and mat to upstands, edges and details
5. Apply main field of resin and mat
6. Apply coloured topcoat (with optional non-slip aggregate)
7. Cure time: 1-2 hours per coat, walkable same day
8. Register 25-year manufacturer warranty

Anti-slip options

For balconies and terraces we can broadcast fine quartz aggregate into the topcoat to create a Class 3 anti-slip surface — meets building regulations for outdoor walkable surfaces.

Warranties

• Material warranty: 25 years (with approved installer scheme)
• Expected service life: 25-30+ years
• Workmanship warranty: 10 years from us

Cost guide

• Typical garage roof (15-20m²): £1,800-£2,800
• House extension (20-40m²): £2,400-£4,800
• Walkable balcony/terrace (10-20m²): £1,500-£3,000
• Large flat roof (50m²+): £5,500-£9,000