Flat roof on its last legs? In 2026, with quotes climbing and every pound counting, more UK homeowners than ever are skipping the roofer and fitting a GRP fibreglass roof themselves. The big question is simple: how much do you actually save — and is it really a job you can do yourself? Short answer: you save mainly the labour — often more than half the fitted cost — and yes, with the right kit, a properly prepared deck and dry weather, fibreglass is one of the most DIY-friendly flat-roof systems there is. Here's the honest breakdown of the costs, savings and work involved. How Much Does a Roofer Charge for a Flat Roof in 2026? For a professionally fitted GRP or felt flat roof in the UK, homeowners are commonly quoted approximately £80–£120 per m² once labour, materials, removal of the old covering, waste disposal, overheads and profit are included. In practical terms: Single garage (~15 m²): typically £1,500–£2,500 or more fitted Larger extension (~30 m²): often £3,000–£4,500 or more fitted The final price depends on your location, roof access, roof condition, required trims, insulation, decking and whether the old roof needs removing. Always get two or three detailed quotes — but the pattern is consistent: labour and installation make up the biggest part of the bill. How Much Does a DIY Fibreglass Roof Kit Cost? This is where DIY GRP roofing delivers the saving. An Apex GRP roofing kit supplies the materials to form the laminate — roofing resin, chopped strand fibreglass matting, Dark Iron Grey topcoat and catalyst — with free UK delivery on qualifying kits. Current options include: 450gsm GRP roofing kits for standard flat roofs — currently from £138.60 600gsm heavy-duty GRP roofing kits for balconies, maintenance access and foot traffic — currently from £158 Kits available in a wide range of sizes, with larger and custom sizes on request Optional tool kits if you don't already own GRP installation equipment Trims, roof decking, insulation and tools may be needed separately depending on your roof. But for that same ~15 m² garage, your materials cost a fraction of a fitted quote — the rest of a roofer's bill is labour you're now doing yourself. → Work out your exact kit in minutes with the free GRP Kit Calculator. DIY Kit vs Hiring a Roofer: The Potential 2026 Saving Cost factorHiring a rooferDIY Apex GRP kit ~15 m² garage ~£1,500–£2,500+ fitted Kit + trims/decking + optional tools Main cost Materials and professional labour Primarily materials Scheduling Depends on the roofer's diary Completed around your own schedule Potential lifespan 20–30+ years (correctly installed) 20–30+ years (correctly installed) Workmanship cover May include an installer's guarantee Materials only — no labour guarantee The saving comes mainly from removing the professional labour cost — the material is the same GRP either way. But a DIY roof must still be done correctly: preparation, weather, resin-to-catalyst ratios and proper consolidation all affect the result. Can You Really Install a Fibreglass Roof Yourself? Yes — provided you're comfortable with practical building work and follow the process carefully. A GRP roof is cold-applied: no roofing torches, naked flames or hot bitumen, which makes it far more approachable than torch-on systems. The main stages are: Remove the failed covering where necessary Check the structure for rotten or damaged timber Fit a clean, dry, securely fixed OSB roof deck Fit the appropriate GRP edge trims Reinforce joints, corners and detailed areas Lay the fibreglass matting Apply and consolidate the roofing resin Allow the laminate to cure Apply the final Dark Iron Grey topcoat If you can prep a clean OSB deck, measure and cut matting, apply resin evenly and consolidate with the correct roller, you can lay a GRP roof. An optional fibreglass tool kit supplies the rollers, brushes, mixing containers and acetone you'll need. New to it? The step-by-step video tutorials cover every stage from timber deck to topcoat. → Everything for the laminate in one box — shop GRP Roofing Kits with free UK delivery. When Should You Hire a Professional Roofer? DIY isn't right for every roof. Consider hiring an experienced roofer if: The structure has extensive rot or damage The design includes complicated outlets, upstands or penetrations Access is difficult or working at height can't be made safe The roof needs structural alterations You're unsure about falls, drainage or ventilation You can't complete the work in suitable dry weather You need a professional workmanship guarantee Saving money matters — but the roof still has to be installed safely and correctly. Which GRP Roofing Kit Should You Buy: 450gsm or 600gsm? The right fibreglass weight depends on how the roof will be used. 450gsm GRP roofing kit — the standard choice for conventional flat roofs: garages, extensions, sheds and workshops, dormers, porches, and any flat roof that won't take regular foot traffic. For most standard domestic projects, 450gsm gives the right balance of strength, cost and ease of installation. 600gsm heavy-duty GRP roofing kit — heavier matting for balconies (tiled or decked), green roofs, maintenance walkways, roofs needing occasional access and areas exposed to extra wear. It uses more resin than 450gsm but creates a heavier, stronger laminate. How Do You Calculate the Correct Kit Size? Measure the actual length and width of the roof in metres and multiply: Roof length × roof width = roof area in m² — e.g. 5 m × 3 m = 15 m² Don't guess quantities or add your own waste — the Apex calculator rounds your roof area up to the nearest available kit size. Use the free GRP Kit Calculator to enter your dimensions, choose 450gsm or 600gsm, add a tool kit if needed, select the right trims for each edge, and drop the finished kit straight into your basket. It stops you ordering too little — or paying for more than you need. What Other Materials Might You Need? The kit supplies the main laminate materials, but a complete project may also need: OSB3 roof decking GRP drip and raised-edge trims, wall flashing trims, expansion trims (larger roofs), internal/external corner trims Roofing outlets and pipe collars, suitable fixings, PU adhesive for trims Additional catalyst for specific temperatures, PPE, a GRP tool kit, and waste-removal materials Inspect the existing roof before ordering so damaged decking, timber or drainage components are in your budget. How Long Does It Take, and How Long Does It Last? A small, straightforward garage roof can be completed over a dry weekend — but removing the old covering, repairing the structure and fitting new decking adds time. Don't rush the prep: the deck must be clean, completely dry, securely fixed and correctly detailed around edges, walls and outlets. A correctly installed GRP roof can last 20–30 years or longer. Lifespan depends on material quality, deck preparation, installation temperature, accurate catalyst measurement, full resin saturation, proper air removal, correctly fitted trims, good drainage and correct topcoat application. The GRP doesn't know whether a homeowner or a professional laid it — but installation quality directly affects performance. Is a DIY Fibreglass Roof Worth It? For a competent DIYer with a straightforward flat roof, the right tools and enough time to follow the process, the answer is usually yes. You get significant labour savings, a seamless waterproof surface with no joints to fail, no naked flames, a long service life and low maintenance — all completed around your own schedule. The biggest risks are poor preparation, incorrect catalyst measurement, unsuitable weather and incomplete consolidation. If you're not confident about any stage, professional installation may be the safer choice. But for many practical homeowners, a complete GRP kit is an affordable way to replace a failing flat roof without paying the full cost of professional labour — and in 2026's market, that's about as good as home-improvement value gets. Frequently Asked Questions How much does a roofer charge to fit a flat roof? Professional flat-roof installation in the UK is commonly estimated at around £80–£120 per m² once materials and labour are included — so roughly £1,500–£2,500 or more for a single garage, depending on access, roof condition and the work required. Can I install a GRP fibreglass roof myself? Yes, if you're confident with practical DIY and can safely prepare the deck, fit the trims, measure the catalyst and apply and consolidate the laminate correctly. GRP is cold-applied, so no roofing torches or naked flames are required. Does an Apex GRP roofing kit include everything? The kit contains the primary materials for the laminate — resin, fibreglass matting, catalyst and Dark Iron Grey topcoat. Depending on your project you may also need trims, OSB decking, fixings and an optional tool kit. How long does a DIY fibreglass roof last? A correctly installed GRP roof can last 20–30 years or longer, depending on material quality, roof preparation, weather conditions and installation quality. What size GRP kit do I need? Measure your roof's length and width and enter them into the free GRP Kit Calculator — it recommends the right kit size and helps you choose trims and tools. Is 450g or 600g fibreglass better? Neither is automatically better. 450g suits most standard domestic flat roofs; choose 600g for balconies, maintenance access, green roofs, foot traffic or heavier-duty applications. Do I need a tool kit? You'll need resin rollers, a consolidation roller, topcoat rollers, brushes, mixing containers, measuring equipment and cleaning materials. If you don't own these, add an optional tool kit when ordering. Can I install a GRP roof in the rain? No. The deck and materials must stay dry throughout. Check the forecast and allow enough dry time to prepare the deck, laminate the roof and apply the topcoat. Start Planning Your DIY Fibreglass Roof Measure your roof and use the Apex GRP Kit Calculator to build the right kit, trims and tools in minutes. For standard flat roofs, explore the 450g GRP roofing kits; for balconies, maintenance access and heavier-duty jobs, view the 600g GRP roofing kits. Free UK delivery, free catalyst — do it once, do it right, and keep the labour in your pocket.
