The test
Three numbers decide it. The building must be at least 18 metres high or have at least 7 storeys, and it must contain at least 2 residential units. Meet the height or the storeys, and the homes, and the building is a higher-risk building for the occupation duties of the Building Safety Act 2022.
Some buildings are left out of the occupation duties even when they are tall enough: care homes, hospitals, hotels, secure residential institutions and military premises. Their fire safety is still governed by other law.
How to measure
The height and the storey count follow set rules, and they are easy to get wrong on a sloping site or a building with plant on the roof.
- 1Measure height from the lowest ground level next to an outside wall to the top of the floor of the top storey, not to the roof or parapet.
- 2Ignore a top storey that holds only roof plant or machinery.
- 3Count storeys above ground only; storeys below ground do not count.
- 4A mezzanine counts as a storey only if its floor area is at least half that of the largest storey above ground.
Registration
A higher-risk building must be registered with the Building Safety Regulator before anyone lives in it. Buildings already occupied had to be registered by 1 October 2023, and letting residents occupy an unregistered higher-risk building is an offence.
The principal accountable person makes the application. Key building information about the structure, the external walls, the roof, the fire and energy systems and more follows within 28 days of applying.
Below the line
A building under 18 metres and under 7 storeys is not higher-risk, but the Regulatory Reform (Fire Safety) Order 2005 still applies to its common parts and any workplace in it: a responsible person, a current fire risk assessment and the measures it calls for.