Flat Roof Installation
and Repair Specialists
in South Wales
From garage roofs to large commercial flat roof systems, we install and repair EPDM, fibreglass, and felt flat roofs that deliver decades of leak-free performance — even in the harshest Welsh conditions.
★ EPDM flat roofs with 50+ year life expectancy as standard
What This Service Involves
Flat roofs are one of the most common roofing structures on extensions, garages, porches, dormers, and bay windows across South Wales. When installed correctly using modern materials, a flat roof can last over 50 years with virtually no maintenance. When installed poorly, it becomes a source of constant leaks and frustration.
Gwent Roofing and Building Maintenance specialises in flat roof installation and repair across Tredegar, Ebbw Vale, Merthyr Tydfil, and the surrounding valleys. We install three primary flat roof systems — EPDM rubber membrane, GRP fibreglass, and traditional built-up felt — each suited to different situations and budgets.
We are approved installers of leading EPDM systems, which means your flat roof comes with both our workmanship guarantee and the manufacturer's material guarantee. This dual protection gives you confidence that your investment is protected for decades.
Whether you need a new flat roof on an extension, a replacement for a failing felt roof, or a repair to an existing system, we deliver clean, precise work that keeps your property watertight.
Why Flat Roofs Fail — and How to Avoid It
The most common reason flat roofs fail prematurely is poor installation. Inadequate preparation of the timber deck, incorrect adhesive application, insufficient overlap at joints, and poor detailing around upstands and outlets all create weak points where water eventually penetrates.
Traditional felt flat roofs — still found on many older properties in the valleys — have a lifespan of only 10 to 15 years. As the felt ages, it cracks, bubbles, and splits, particularly in areas exposed to direct sunlight. Many homeowners patch these repeatedly instead of replacing with a modern system.
Ponding is another major issue. If your flat roof does not have adequate falls (a minimum 1:40 gradient), rainwater pools on the surface. Standing water accelerates material degradation, adds weight stress to the structure, and eventually finds a way through. A properly designed flat roof sheds water to outlets and gutters efficiently.
Poor ventilation of the roof void below a flat roof causes condensation, which mimics a leak from above. Homeowners often blame the membrane when the real problem is trapped moisture vapour. We install appropriate ventilation to prevent this issue entirely.
How We Work
Survey & Assessment
We inspect the existing structure, check timber condition, assess falls, and determine the best flat roof system for your property and budget.
Detailed Specification
You receive a clear specification detailing the system, materials, insulation, and finish — along with a fixed-price quote.
Deck Preparation
We strip the old covering, inspect and replace any damaged timber, install insulation boards, and prepare a clean, dry deck surface.
System Installation
Your chosen flat roof system is installed with precision — every joint sealed, every upstand detailed, every outlet trimmed and watertight.
Testing & Handover
We flood-test the roof where possible, check all details, and hand over your guarantee documentation.
Why Homeowners Choose Us
50+ Year Lifespan
EPDM rubber membrane flat roofs carry a life expectancy exceeding 50 years. Install once and forget about it.
No Maintenance Required
Modern flat roof systems require virtually no maintenance — no painting, no re-coating, no annual checks.
Lightweight & Strong
EPDM and GRP are lightweight materials that do not add structural load, making them ideal for extensions and garages.
Manufacturer Guarantee
As approved installers, your flat roof is covered by both our workmanship guarantee and the manufacturer's product warranty.
Rapid Installation
Most flat roof installations are completed in 1 to 3 days, minimising disruption to your home.
Improved Insulation
We install high-performance insulation boards that improve thermal efficiency and reduce heating costs.
Flat Roof Systems Explained
EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber membrane that has become the gold standard for domestic flat roofing. It is supplied in large single sheets, which means most domestic flat roofs can be covered with no joints at all — eliminating the most common failure point. EPDM is UV stable, ozone resistant, and remains flexible across a temperature range of -45°C to +130°C.
GRP (Glass Reinforced Polyester) fibreglass is our recommendation for walkable flat roofs, balconies, and areas where a hard-wearing finish is required. GRP is applied as a liquid resin with fibreglass matting, creating a seamless, rigid shell. It is extremely durable, has a life expectancy of 25 to 30 years, and can be finished in a range of colours including anti-slip textures.
Traditional built-up felt systems use multiple layers of bituminous felt bonded with hot or cold adhesive. While felt is the most affordable flat roof option, it has a shorter lifespan (10 to 15 years) and requires more maintenance. We still install felt systems where budget is the primary concern, but we always advise homeowners of the long-term cost comparison with EPDM.
Insulation is a critical component of any flat roof installation. We use high-performance rigid insulation boards (typically Celotex or Kingspan) installed above the deck to meet current Building Regulations Part L requirements. This not only keeps your home warmer but also prevents interstitial condensation — a common cause of damp problems beneath flat roofs.
Upstand details, edge trims, and outlet connections are where flat roof quality is truly tested. We use proprietary trim systems matched to each membrane type, ensuring clean, secure, and watertight termination at every edge, wall junction, and drainage point.
For properties in the upper valleys where wind exposure is significant, we specify mechanically fixed membrane systems rather than fully adhered. This provides superior wind uplift resistance and is essential for exposed locations around Ebbw Vale, Blaenavon, and the Heads of the Valleys corridor.
Frequently Asked Questions
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