Description
EPDM rubber isn't the only way to waterproof a flat roof — GRP fibreglass is the other system UK roofers reach for, and some jobs simply suit it better: roofs with lots of foot traffic, complex details and corners, or owners who want a hard, seamless, walk-on surface with a crisp trimmed edge.
This kit gives you the complete GRP system for a new deck, sized by roof area, with the tools included — resin, topcoat, catalyst, matting, tape, rollers, brushes and buckets in one box.
Key benefits
- Complete system in one kit — 450g fibreglass matting, base resin, grey topcoat, catalyst, woven tape, laminating and paddle rollers, brushes, buckets and gloves
- Cures to a hard, seamless, fully walkable waterproof surface with no joints or seams
- Cold-applied — no torches or hot works on the roof
- Six kit sizes, matched to your roof area from a 5m² porch to a 30m² garage roof
- The proven GRP wet-lay system used across UK domestic flat roofing
Suitable applications
New flat roof decks on garages, extensions, porches, sheds, garden rooms, dormers and balconies — anywhere you're boarding a new deck (GRP is laid onto new OSB3, not over old felt) and want a hard-wearing seamless finish.
Prefer a rubber membrane instead?
Our Complete EPDM Flat Rubber Roof Kit covers the same roofs with a one-piece EPDM membrane — GRP suits heavy foot traffic and complex detail; EPDM suits speed, flexibility and larger single sheets.
If your roof sits close to a boundary or needs a fire-rated covering under Building Regulations, see our Fire-Rated GRP Roofing Kit (BROOF(t4)) — the same sizes and process, with a fire-rated resin and topcoat.
Specification
| Kit size | Covers | Matting | Topcoat colour | Tools included |
|---|---|---|---|---|
| 5m² kit | Up to 5m² | 450g CSM | Grey | Yes |
| 10m² kit | Up to 10m² | 450g CSM | Grey | Yes |
| 15m² kit | Up to 15m² | 450g CSM | Grey | Yes |
| 20m² kit | Up to 20m² | 450g CSM | Grey | Yes |
| 25m² kit | Up to 25m² | 450g CSM | Grey | Yes |
| 30m² kit | Up to 30m² | 450g CSM | Grey | Yes |
Each kit contains base resin, grey GRP topcoat, catalyst (MEKP), 450g chopped strand matting, 50mm woven tape, laminating and paddle rollers, brushes, mixing buckets, gloves and an installation guide.
Installation & ordering guidance
Measure your roof deck area in m² and order the kit size at or above it — if you're between sizes, size up, since detail work around edges and upstands uses more material than the flat field.
GRP is laid onto a clean, dry, new OSB3 deck in dry weather above roughly 5°C: catalysed resin wets out the matting, cures within the hour, and the pigmented topcoat seals and finishes the surface.
To finish the perimeter properly, add our GRP roof edge trim perimeter packs — the laminate is taken out over the trim's fixing arm and sealed in, giving a straight, weathertight edge in black, grey or white.
For the tools you'll reuse on any roofing job, see our Professional Installation Kit.
FAQs
GRP or EPDM — which should I choose?
Both waterproof a flat roof for decades.
GRP gives a hard, seamless walk-on surface that shrugs off ladders and foot traffic and excels at fiddly details; EPDM goes down faster in one flexible sheet and tolerates structural movement better.
If you're unsure, our team can advise against your actual roof.
Can I lay this over my old felt roof?
No — GRP needs a new, dry OSB3 deck to bond to.
If you're overlaying an existing covered roof, an EPDM system or a liquid coating is usually the better route.
How much time do I have once the resin is mixed?
Working time is typically 20–30 minutes per mix depending on temperature — mix in batches you can use immediately rather than catalysing the whole tin.
Which kit size do I need?
Match the kit to your measured deck area and round up — e.g. a 3.5m × 5m garage (17.5m²) takes the 20m² kit.
How is it delivered?
As a multi-box kit on a courier or pallet service depending on size; resins are date-sensitive, so order close to your planned installation and store cool until use.
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