Most people searching for flat roofing materials end up with twelve browser tabs open and a vague sense of dread. You came in needing to sort a flat roof. You leave having learned that there are several systems, multiple spec levels, and no obvious answer. GRP (glass reinforced plastic) is one of the more reliable options available in the UK. No joins, no seams, handles British weather without complaint, and when it's installed correctly it can last 25 years or more. The catch is that there are three different GRP systems, and picking the wrong one, or over-specifying when a basic kit would do the same job, costs real money. What follows is a breakdown of all three: what each one does, where it makes sense, and where it doesn't. Route 1: Budget GRP Kit Small & Large Fibreglass Repair Kits Complete, all-in-one solution for creating, moulding, and repairing GRP. View product → Standard · 450g GRP Roofing Kit – Dark Iron Grey Perfect for garages, extensions & standard flat roofs. 25+ year lifespan. View product → Who it's for "Budget" doesn't mean flimsy. It means you're not paying for reinforcement you don't need. The budget GRP kit is built for smaller, lighter-use jobs: a shed roof, a small repair on an existing GRP surface, a minor extension that sees no foot traffic. If your roof is under roughly 10-15m² and nobody's walking on it, this covers what you need. Going heavier just means spending money on performance you'll never use. It won't handle regular foot traffic, suit exposed or high-stress areas, or match the longevity of the heavier systems. If people are walking on it, skip this one and go straight to Route 3. → Shop Budget GRP Kits Route 2: Standard Dark Grey GRP System Waterproofing Repair Kit Apex Owl LAVA 20 Seamless Flexible UV-Resistant(Free Delivery) View product → Single-coat flat roofing system Cure It ONE Roof Kits Anthracite Grey, Fast Single Coat Application, 20-Year Guarantee. View product → Who it's for Most residential flat roofs in the UK end up on this system, and it's not hard to see why. The 450gsm dark grey GRP system is strong enough for a proper residential roof, works across most substrates, and comes with a dark grey topcoat that gives a clean, finished look. Garages, extensions, bay window tops, canopy roofs, most trade installations where the surface sees normal residential use. This is what most of those projects spec. If you want a single-coat option with a 20-year guarantee, the Cure-It ONE system also sits in this tier. Faster to apply, cures quickly, same category of job. Worth knowing before you buy anything: the kit is only as good as the prep underneath it. A premium system laid over a poorly prepared substrate will fail before a budget kit that's been properly primed and laminated. If you're doing this yourself, the HSE's guidance on resin handling is worth reading before you start. → Shop Standard GRP Systems Route 3: 600g Heavy-Duty GRP Kit Fire Retardant Kit ResTec 1010 600grm Heavy Duty Meets all Building Regs 20 Year Guarantee (Trims @ £9.60 ) View product → Strong, Durable & Easy to Install Balcony - Double Layer Two layers of premium 450g fibreglass matting, creating a 900g total laminate. View product → Who it's for Some roofs just take more punishment. Balconies get walked on every day. Rooftop terraces see furniture, plant pots, constant foot traffic. Commercial buildings need fire compliance. None of that is the right situation for a 450gsm kit. The 600gsm heavy-duty system uses heavier matting and in some configurations a double-layer laminate. The result is a thicker, more rigid membrane that handles load, impact, and exposure far better. For anything needing fire-rated performance, which Building Regulations Approved Document B may require depending on your project, the Pro-25 600gsm fire retardant kit and the Silverseel BRoof(t4) kit both carry the relevant certification. Check the Planning Portal's flat roof guidance if you're unsure whether your project needs to comply. → Shop Heavy-Duty 600g Kits Which System for Which Project? Project Type Recommended System Shed roof / small repair Budget GRP kit Garage or small extension roof Standard 450gsm Residential flat roof (15–40m²) Standard 450gsm Balcony or walkable terrace 600gsm heavy-duty Rooftop terrace / communal area 600gsm double-layer Any roof needing fire certification 600gsm fire-rated kit Still Not Sure? Three questions settle it for most people: Does anyone regularly walk on it? Yes → 600gsm. Maintenance access only → standard is fine. Never → budget may do. Does it need fire-rated performance? Yes → 600gsm fire-rated only. How big is the area? Under 15m² with light use → budget. Larger residential → standard. Load-bearing, exposed, or complex → 600gsm. → Browse All GRP Roofing Kits What Our Customers Say ★★★★★ Rated 5.0 out of 5 from 490 reviews on Trusted Shops. Here's what recent customers said: ★★★★★ "Very good product, excellent communication - they go above and beyond to help. Well recommended to others." Verified Customer • July 2025 ★★★★★ "Good communication. Kept me updated from the start, good range of products. Quality is great and price is competitive." Verified Customer • June 2025 ★★★★★ "My first time buying glass fibre, they replied promptly when I needed advice. If the product is half as good as the service, I'll be pleased." Verified Customer • June 2025 Need Help With the Rest of Your Kit? GRP roofing isn't just resin and matting. Getting the trims and edging right makes a real difference to the finished result, especially at corners and perimeters. If you're new to GRP, the installation tutorial videos on our site are worth watching before you start. → View GRP Trims & Edging Call us on 0800 612 7903 or browse the full range at apexfibreglassroofingsupplies.co.uk.
