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Resin Flat Roof Installation

A resin flat roof—typically installed using GRP (Glass Reinforced Plastic) or PU (Polyurethane) liquid systems—creates a seamless, durable, and watertight membrane ideal for modern flat roofing. The installation process combines specialist materials with precision workmanship to ensure long-term performance.

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Required Products & Materials

While exact materials depend on the chosen resin system, the following components are commonly used:

Base & Reinforcement Materials

  • OSB3 or plywood decking (structural base)

  • Fibreglass matting (for GRP systems)

  • Non-woven reinforcement fleece (for PU/PMMA systems)

Resins & Coatings

  • Primer (improves adhesion to the deck)

  • Base resin (polyester resin for GRP, PU or PMMA resin for liquid systems)

  • Topcoat (UV-resistant finish)

  • Catalyst or hardener (for GRP resin curing)

Edge Trims & Accessories

  • GRP edge trims (drip trims, kerb trims, upstands)

  • Jointing tape or reinforcement tape

  • Roofing screws and fixings

Tools & Equipment

  • Resin rollers and brushes

  • Mixing buckets

  • Paddle mixer

  • Angle grinder or saw (for trims)

  • PPE: gloves, respirator mask, goggles

Flat roof GRP.jpg
GRP-Roofing-Contractors.jpg

Installation Process

Although techniques vary slightly between resin systems, the typical installation follows this structure:

Step 1: Preparation

  1. Inspect the existing roof structure for damage or moisture.

  2. Install new OSB3 decking if required, fixing it securely to the joists.

  3. Ensure the roof surface is clean, dry, and dust-free.

  4. Fit all GRP edge trims and flashings around the perimeter.

Step 2: Priming

  1. Apply primer to the decking to improve adhesion.

  2. Allow primer to cure as per manufacturer guidelines.

Step 3: Laminating / Base Layer

For GRP systems:

  • Mix the polyester resin with catalyst.

  • Lay the fibreglass matting across the deck.

  • Saturate the matting with resin using rollers, ensuring an even, bubble-free laminate.

For PU/PMMA systems:

  • Apply the base resin directly to the deck.

  • Embed the reinforcement fleece into the wet resin.

  • Apply another layer of resin over the fleece.

Step 4: Curing

  • Allow the laminated base to cure fully.

  • Cure times depend on temperature and resin type (often 30–90 minutes for PMMA, several hours for GRP).

Step 5: Topcoat Application

  • Apply a UV-stable topcoat evenly across the roof.

  • This protects the system from weathering, sun exposure, and mechanical wear.

Step 6: Final Inspection

  • Check for proper curing, seamless coverage, and correct drainage fall.

  • Ensure all trims and edges are sealed.

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