How to repair a flat roof (UK Homeowner Guide – 2025)

Flat roofs are popular on UK garages, extensions, and porches — but they’re also known for developing leaks, cracks, and pooling water over time.

So if you’re searching

“How to repair a flat roof?”

This guide will walk you through the essentials:

what you can do yourself, what you shouldn’t touch, and when it’s time to call a professional.

Let’s break down how flat roof repairs really work in 2025.

🔹 Identify the Type of Flat Roof You Have

Before you even think about repairing it, you must know what material it uses:

EPDM Rubber Roof

Flexible, single sheet, long-lasting.

Typical issues: splits, punctures, loose edges.

GRP Fibreglass Roof

Hard, smooth surface, seamless.

Typical issues: cracks, pinholes, blistering.

Torch-On Felt Roof

Older style.

Typical issues: cracking, blistering, poor joins.

Different materials need different repair techniques — get this wrong and the repair won’t last.

🔹 Find the Source of the Leak

Most flat roof leaks come from:

• Cracks or splits in the material

• Loose edge trims

• Standing water (ponding)

• Failed joins or seams

• Damaged flashing

• UV deterioration

• Blistered patches

Flat roof leaks often travel sideways, so the wet patch inside your home might not be directly under the problem.

🔹 Repairing an EPDM (Rubber) Flat Roof

Best for: garages, extensions, dormers

Lifespan: 20–25 years

EPDM repairs are straightforward — if you know what you’re doing.

Small splits or punctures can be repaired by:

• Cleaning the area

• Applying EPDM primer

• Installing a rubber patch with roller pressure

• Sealing edges with EPDM adhesive

Larger issues need professional repair:

• Loose membranes

• Failing seams

• Water trapped underneath

• Structural problems

Because EPDM repairs require special primers and patches, most homeowners prefer a specialist.

🔹 Repairing a GRP Fibreglass Roof

Best for: extensions, visible areas

Lifespan: 25+ years

GRP repairs are harder than EPDM because the material is rigid.

Minor cracks can be repaired with:

• Cleaning the crack

• Sanding the area

• Applying resin

• Reinforcing with matting

• Finishing with a new topcoat

Blistering or delamination requires professional help, as the top layer must be cut back and rebuilt properly.

🔹 Repairing a Traditional Felt Roof

Felt roofs are common on older Telford homes.

Small repairs include:

• Cutting away blisters

• Letting trapped air escape

• Re-fusing with heat

• Applying bitumen and a patch

But felt repairs often fail again later — once felt deteriorates, replacement is usually the best long-term option.

🔹 When NOT to Repair a Flat Roof Yourself

DIY repairs can make things worse if you notice:

• Water pooling for more than 48 hours

• Large cracks or widespread blistering

• Damage around roof edges

• Issues with structural timber

• Leaks coming from flashing

• Rotten or perished underlay

These problems need a proper inspection — a patch won’t fix them.

🔹 When It’s Time for a Full Flat Roof Replacement

Sometimes repairs cost more long term than replacing the roof.

You may need a new flat roof if:

• The roof is over 20–25 years old

• Multiple leaks have appeared

• Moss and water damage keep returning

• The material has perished

• The roof deck is soft or sagging

Modern EPDM and GRP systems last much longer and offer excellent waterproofing.

🔹 How Much Do Flat Roof Repairs Cost in the UK?

Typical repair costs:

• Minor EPDM repair: £80–£250

• Minor GRP repair: £120–£350

• Felt patch repair: £60–£180

• Edge trim repair: £50–£150 per metre

• Flashing repair: £150–£450

New flat roof installation:

• EPDM: approx £70 per m²

• GRP: higher cost, premium lifespan

The Best Way to Repair a Flat Roof? Get It Checked Properly

Flat roofs can be tricky — water behaves differently on them, and small cracks often hide bigger issues underneath.

At Correct Way Roofing, we provide:

✔ Free flat roof inspections

✔ Honest advice (repair or replace)

✔ EPDM & GRP repairs

✔ Same-day emergency patching

✔ Long-lasting, guaranteed fixes

✔ Local Telford specialists

Before you spend money on a repair product that might not work, let a professional assess the real cause.

📞 Call Correct Way Roofing for a free on-site inspection and honest price estimate.

Call Us Today