Understanding Part B: Fire Safety Requirements for Buildings in England

Approved Document B (Fire Safety) provides guidance on meeting the fire safety requirements of the Building Regulations 2010 in England. It is published in two volumes: Volume 1 (dwellinghouses) and Volume 2 (all other buildings). Part B has five functional requirements: B1 (Means of Warning and Escape), B2 (Internal Fire Spread – Linings), B3 (Internal Fire Spread – Structure), B4 (External Fire Spread), B5 (Access for the Fire Service).

Fire Detection and Alarm

New dwellinghouses need mains-powered interlinked smoke alarms on each floor, a heat alarm in the kitchen, and carbon monoxide alarms in rooms with combustion appliances.

Means of Escape

Bedrooms in two-storey houses need escape windows: minimum 0.33m² opening, 450mm minimum height and width, sill no more than 1,100mm above floor. Houses of three or more storeys require a protected stairway in fire-resisting construction with self-closing fire doors throughout.

Fire Doors

FD20 doors (20 min resistance) for dwellings; FD30 (30 min) for flat entrance doors and compartment walls; FD60 (60 min) for higher-risk applications. All fire doors must have self-closers and be correctly installed in fire-resisting frames.

External Wall Systems

Buildings over 18m (and from December 2024 over 11m) must have external wall systems entirely of Class A1 or A2 materials. Combustible cladding and insulation is banned in high-rise residential buildings following the Grenfell Tower fire.

Higher-Risk Buildings and the Building Safety Act 2022

Residential buildings 18m+ or 7 storeys+ with 2+ residential units are higher-risk buildings (HRBs). The Building Safety Regulator (BSR) is the building control authority for HRBs. A Gateway regime applies with mandatory sign-off at three project stages. Sprinklers are mandatory in residential buildings over 11m.

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