If you're considering a flat roof replacement or installation, you've probably heard about GRP fibreglass roofing. It's one of the most popular modern flat roofing solutions, and for good reason. But what exactly is GRP, how does it work, and is it the right choice for your property?
In this comprehensive guide, we'll explain everything Hampshire homeowners need to know about GRP roofing — from how it's installed to how much it costs, and why it outperforms older alternatives like felt and EPDM rubber.
What Is GRP Fibreglass Roofing?
GRP stands for Glass Reinforced Plastic, also known as fibreglass. It's a modern, seamless waterproof coating system that's applied directly to your flat roof surface to create a durable, weatherproof barrier. Unlike traditional felt or EPDM roofs that have seams and joins, GRP creates a completely seamless roof with no leak points.
GRP is made from layers of fibre mat and polyester resin, creating a material that's incredibly tough, flexible, and long-lasting. The result is a roof that can typically last 25-50+ years with minimal maintenance — significantly longer than felt (10-15 years) or EPDM (20-30 years).
How Is GRP Fibreglass Roofing Installed?
The GRP installation process is straightforward but requires skilled professionals to get right. Here's what happens:
Step 1: Surface Preparation
Your existing roof is thoroughly cleaned and prepared. If there's old felt or EPDM, it can be removed or left in place as a base, depending on its condition. The surface is cleaned to ensure the new coating adheres properly.
Step 2: Primer Application
A primer coat is applied to seal the substrate and ensure proper adhesion of the GRP layers.
Step 3: Fibre Mat and Resin Application
Layers of fibre mat and polyester resin are applied directly to the roof. These layers bond together to create a strong, flexible, waterproof membrane. The process typically involves laying fibre mat, then saturating it with resin, building up multiple layers for strength and durability.
Step 4: Final Topcoat
A final protective topcoat is applied. This can be a white reflective coating (to reduce heat and UV damage), a coloured finish, or a specialist protective layer depending on your preferences and requirements.
The entire installation is seamless — there are no joints or seams where water could penetrate. This is a major advantage over EPDM, which relies on sealed seams that can deteriorate over time. A typical GRP roof installation can be completed in just 1-2 days, minimizing disruption to your home or business.
Key Benefits of GRP Fibreglass Roofing
1. Exceptional Longevity (25-50+ Years)
A properly installed GRP roof will last 25-50 years or more — substantially longer than felt (10-15 years) or EPDM (20-30 years). This means fewer replacements over your lifetime and better value for money.
2. Seamless and No Leak Points
Unlike EPDM or felt roofs with seams and joints, GRP is completely seamless. There are no joins for water to exploit, meaning fewer leaks and less maintenance. Once installed, you can forget about it.
3. Low Maintenance
GRP requires minimal maintenance compared to other roofing types. Occasional cleaning and inspection is all that's needed. No constant patching or repairs like felt roofs require.
4. Excellent Aesthetics
GRP comes in various finishes and colours. The white reflective finish looks clean and modern, and the topcoat can be customized to match your preferences or property style. It's far more attractive than aging felt or EPDM.
5. Walkable Surface
GRP is tough enough to walk on without damage (unlike some roofing materials), making maintenance, cleaning, and future repairs much easier. You won't damage the roof by accessing it for inspections or maintenance.
6. Fast Installation
Most GRP roofs are installed in 1-2 days. Compare this to other roofing methods that might take longer. Quick installation means less disruption and faster completion of your project.
7. Environmentally Friendly
GRP is durable and long-lasting, which means it needs replacing less often than short-lived alternatives like felt. The longer lifespan means less waste and fewer replacements — better for the environment.
GRP vs. Felt vs. EPDM: A Detailed Comparison
| Feature | GRP Fibreglass | Felt | EPDM Rubber |
|---|---|---|---|
| Expected Lifespan | 25-50+ years | 10-15 years | 20-30 years |
| Installation Time | 1-2 days | 1-2 days | 1-2 days |
| Seams/Leak Points | None (seamless) | Multiple (joints) | Multiple (seam-based) |
| Maintenance Required | Minimal | High (frequent repairs) | Moderate |
| Walkable | Yes | No (easily damaged) | Yes |
| Cost per m² | £70-£120 | £30-£60 | £50-£100 |
| Long-term Value | Excellent | Poor (frequent replacement) | Good |
| UV Resistance | Excellent | Poor (fades and cracks) | Good |
| Aesthetics | Modern, attractive | Basic, ages poorly | Acceptable |
GRP Roofing Costs in Hampshire
How much does GRP roofing cost? The typical price range is £70-£120 per square metre installed, though this varies based on several factors:
- Roof size: Larger roofs typically cost less per m² due to economies of scale. A 50m² garage roof will cost more per m² than a 200m² extension.
- Roof access: Difficult-to-access roofs (steep pitches, complex shapes) cost more due to safety requirements and additional setup time.
- Existing roof condition: Removing old felt or EPDM adds cost. Leaving existing roofing in place (if it's sound) can reduce costs.
- Additional work: New flashing, guttering repairs, or structural work will add to the total cost.
- Location: While we work across Hampshire, some rural areas may have slightly higher travel costs.
For a typical 100m² flat roof replacement in Hampshire, you'd expect to pay £7,000-£12,000 fully installed. At CMW Roofing, we provide detailed quotes after surveying your roof, so there are no surprises.
Is GRP Suitable for My Roof?
GRP roofing works well on most flat or low-pitch roofs, including:
- Garage roofs
- Flat roof extensions
- Bay window roofs
- Balconies
- Summer houses and garden rooms
- Commercial building roofs
- Dormer roofs
If you have a pitched tile roof on your main house, GRP isn't the solution — you'd need tile repair or replacement. But for any flat roof or low-pitch area, GRP is an excellent choice.
Our GRP Roofing Guarantee
At CMW Roofing, we're confident in the quality of our GRP installations. We provide a 15-year guarantee on all new GRP roofs, giving you peace of mind that your roof is protected. We use quality materials and proven installation techniques to ensure your roof performs for decades to come.
Next Steps: Get a Free Quote
If you're considering GRP fibreglass roofing for your flat roof, the best next step is a free survey and quote from our experienced team. We'll assess your current roof, discuss your options, and provide a no-obligation quote for GRP installation or any other roofing solution.
CMW Roofing specialises in flat roof repair and installation across Hampshire and Southampton. Whether you need a complete GRP roof installation or have questions about repairs and maintenance, we're here to help.
Contact us today for a free GRP roofing quote and let's get your flat roof the protection it deserves.