A fire rated GRP roofing kit has been independently tested to BS476 Part 3, confirming it meets the external fire spread requirements of UK Building Regulations Approved Document B. It is not a marketing term — it is a documented classification. Without it, your roof will not pass Building Control on any project where fire rating is required.

Under Approved Document B, any roof within one metre of a property boundary must use fire-resistant materials. This applies to extensions, flat roof replacements, garages, and outbuildings. If your roof sits within that boundary distance, a standard GRP kit is non-compliant. A fire rated kit is not optional in that situation.

No. Standard GRP kits contain no fire retardant chemistry and carry no BS476 classification. Only specifically formulated systems — Silverseel, Cure-It Fire Retardant, Res-Tec 100, Pro 25, and Metrodeck — meet the fire rating requirement. If the product listing does not reference BS476 Part 3, it is not fire rated.

The gsm refers to the weight of the chopped strand matting in the laminate. 450gsm is for standard flat roofs with no foot traffic. 600gsm is for balconies, terraces, and any area that will bear regular foot traffic. Both weights can carry the same BS476 fire classification — the gsm is a structural decision, not a fire performance decision.

For a standard garage flat roof with no foot traffic, Res-Tec 100 450gsm or Cure-It Fire Retardant 450gsm are the go-to options — both meet BS476 Part 3, both carry a manufacturer guarantee, and both are suitable for competent DIY installation. If the garage roof doubles as a walkable area, move to the 600gsm version of either system.

Yes, for domestic projects under Permitted Development. There is no legal requirement for a certified installer. The fire retardant chemistry is already built into the resin and topcoat — the application process is the same as standard GRP. What matters is correct surface preparation, correct catalyst ratios, and correct application temperature as per the product datasheet. For commercial projects, confirm installer requirements with the system manufacturer before proceeding.

Measure your roof area in square metres, then add 10% for wastage, laps, and edge detailing. Include upstands and trim areas — not just the flat deck. Coverage details are shown on each product page. You can also use our GRP roofing kit calculator to estimate the correct kit size for your roof before ordering. If you are unsure, call Apex on 0800 612 7903 before ordering. Under-ordering mid-job creates a compliance gap and a potential batch colour mismatch.