Why GRP Roofs Fail and Leak – Common Issues in Milton Keynes & Surrounding Areas

Written By simon reading

GRP (Glass Reinforced Plastic), also known as fibreglass roofing, is a popular choice for flat roofs across Milton Keynes, Newport Pagnell, and the wider Buckinghamshire area. Known for its clean finish and long lifespan, GRP is widely used on garages, extensions, and commercial properties.

But even the most reliable flat roofing systems can go wrong. If you've noticed leaking, cracking, or bubbling on your GRP roof, you're not alone. In this blog, we explain the most common reasons GRP roofs fail – and what you can do to fix it.

1. Poor Installation

By far the most common issue we see with leaking GRP roofs in Milton Keynes is poor installation. Fibreglass roofs need to be laid with care and attention to detail. If the surface isn't properly prepared, or the resin isn't applied evenly, the roof is far more likely to fail.

Signs of poor GRP installation include:

  • Water pooling or not draining properly

  • Air bubbles or blisters

  • Cracks along the edges or trims

Local Tip: Always use an experienced flat roofing contractor who specialises in GRP. At All Weather Roofing Ltd, we’ve repaired dozens of poorly installed fibreglass roofs across Newport Pagnell and beyond.

2. Curing Issues Due to Bad Weather

GRP roofs need to cure (harden) in the right conditions. If the roof is laid when it's too cold, damp, or raining – which is often the case in unpredictable UK weather – the resin may not bond properly.

This can lead to:

  • A soft or tacky surface

  • Poor adhesion to the deck

  • Leaks and premature deterioration

3. No Room for Expansion

Fibreglass naturally expands and contracts with changes in temperature. If your GRP roof hasn’t been fitted with proper expansion joints, it could crack over time – especially around rooflights, skylights, or upstands.

This is something we regularly see in older roofs around Milton Keynes and Bletchley that weren’t installed with enough flexibility in mind.

4. Physical Damage

While GRP is strong, it’s not immune to damage. Foot traffic, falling branches, or sharp tools can cause small punctures that lead to leaks.

Common causes of GRP roof damage:

  • Tradespeople walking on the roof

  • Misplaced ladders

  • Debris from nearby trees

5. Lack of Maintenance

Like any flat roofing system, GRP requires occasional maintenance. If outlets become blocked, or small cracks are ignored, water can begin to seep in.

We recommend:

  • Annual roof inspections

  • Cleaning debris from gutters and outlets

  • Checking trims and edges for wear

How to Fix a Leaking GRP Roof

If your GRP roof is leaking or showing signs of failure, don’t leave it to worsen. At All Weather Roofing Ltd, we provide:

  • Detailed GRP roof inspections

  • Affordable fibreglass roof repairs

  • Complete GRP replacements if required

Need GRP Roof Repairs in Milton Keynes or Newport Pagnell?

We serve homes and businesses across:

  • Milton Keynes

  • Newport Pagnell

  • Bletchley

  • Olney

  • Buckingham

  • Bedford

Our experienced team specialises in flat roofing and GRP repair solutions throughout Buckinghamshire and Bedfordshire.

Get Your Free Quote Today

📞 Call us on 01908 562077

📧 Or email ALLWEATHEROOFINGLTD@GMAIL.COM

All Weather Roofing Ltd – Trusted flat roofers in Milton Keynes, Newport Pagnell, and surrounding areas.

simon reading
Next

How a New Flat Roof Can Increase Property Value