UK Building Regulations and Approved Documents (B, C, L)

In England, building work must comply with the Building Regulations, a set of legal functional requirements. The government publishes Approved Documents as statutory guidance on ways to meet them. Following an Approved Document is not mandatory, but doing so is normally accepted as evidence of compliance. Wales, Scotland and Northern Ireland have their own regulations and guidance with similar subjects but different detail.

The Approved Documents are labelled by Part, from A (Structure) through T (Toilet accommodation), plus guidance on Regulation 7 (materials and workmanship). Three are especially important for roofs.

Approved Document B – Fire safety

Part B deals with fire safety, including the external fire performance of roofs. Roof coverings near boundaries and on certain buildings must meet minimum classes, expressed using the European classification of EN 13501-5 (for example BROOF(t4)). It also covers fire spread at junctions between roofs and compartment walls, and the materials used in and on roofs of taller buildings. Approved Document B has been revised repeatedly since the Grenfell Tower fire in 2017; the government's collection page lists an update in September 2026.

Approved Document C – Site preparation and resistance to contaminants and moisture

Part C requires roofs to resist the passage of moisture from outside and to avoid harmful condensation. It points to British Standards for detailed guidance, notably BS 5534 for slating and tiling, and to British Standards on moisture management. The current edition dates from 2013 with later amendments.

Approved Document L – Conservation of fuel and power

Part L sets energy-efficiency standards, including maximum U-values for roofs in new buildings and for work on existing roofs. Replacing a roof covering on an existing dwelling is often "renovation of a thermal element," which can trigger a requirement to upgrade insulation where technically and economically feasible. The collection page lists the current version as updated in February 2023.

Other relevant parts

• Part A – structural safety, including wind and snow loads, using Eurocodes such as EN 1991-1-4 with UK National Annexes.
• Part F – ventilation.
• Part K – protection from falling, relevant to roof access.
• Regulation 7 – materials and workmanship.

Building control

Compliance is checked by local authority building control or registered building control approvers. Competent person schemes allow registered roofing contractors to self-certify certain work, such as re-roofing, in England and Wales.