BROOF(t4): What You Need to Know
BROOF(t4) is the highest fire performance rating for flat roof systems. Since the Building Safety Act 2022, it has become a key requirement for demonstrating compliance and ensuring buildings are protected against external fire spread.
Why It Matters
Flat roofs are large exposed surfaces. In an external fire, flames and burning debris can travel quickly across a roof that isn’t properly tested. This risk is greater in built‑up areas where buildings are close together.
When BROOF(t4) Is Required
Roofs within 6 metres of a boundary usually need a BROOF(t4) classification. Many designers and Building Control Officers also specify it beyond 6 metres to maximise safety and future‑proof the building.
What BROOF(t4) Tests
BROOF(t4) assesses the entire roof system, not individual products. A full roof build‑up is tested to ensure:
Fire does not penetrate the roof
Flames self‑extinguish within five minutes
Flame spread stays below 380mm
This confirms the roof can resist external fire and limit spread between buildings.
Consequences of Non‑Compliance
Failing to meet fire safety requirements can lead to:
Financial penalties
Stop notices
Costly remedial work
Legal action or prosecution
Getting Specification Right
Compliance requires evidence that the whole roof system has been tested and classified correctly. Keeping documentation and reviewing fire performance early in design helps avoid delays and redesigns.