In short
- In occupation, a higher-risk building is 18m+ or 7+ storeys with at least two residential units.
- Height is measured from ground level to the top floor surface of the top storey, ignoring roof-top plant storeys.
- Hotels, care homes and hospitals are excluded only if the whole building is that use. Student halls are in scope.
- In-scope buildings must be registered and have an accountable person, a safety case and a golden thread.
The test for occupied buildings
Under section 65 of the Building Safety Act 2022 and the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023, an occupied building is a higher-risk building (HRB) if it:
- is at least 18 metres high or has at least 7 storeys, and
- contains at least two residential units, and
- isn't an excluded building.
A residential unit is a unit of living accommodation – a flat, a studio, a room in an HMO, a university hall bedroom or a supported-housing unit. Tenure doesn't matter, and short-term lets count.
How to measure height
Measure from ground level to the top of the floor surface of the top storey. Ignore any top storey that consists only of roof-top machinery or plant rooms. On sloping ground, use the lowest part of the ground next to the building.
Common mistakes are measuring to the roof or parapet, or including a plant room storey. The government's FRAEW quality guidance lists "roof plant included in the height" as a red flag for the same reason.
How to count storeys
When counting storeys, ignore:
- Storeys below ground – any storey with part of its finished ceiling below the adjacent ground level
- Storeys consisting only of roof-top machinery or plant rooms
- Galleries and mezzanines with a floor area under 50% of the largest storey above or below them
The government's current position is that open roof gardens are not storeys, but this has been challenged at tribunal, so take advice on borderline cases.
Which buildings are excluded
A building is excluded only if it consists entirely of a care home, hospital, secure residential institution, hotel or military barracks, or contains certain defence accommodation. Mixed-use buildings are not excluded – a block with a hotel on the lower floors and flats above can still be an HRB. Student accommodation is not excluded.
Where a structure has independent sections – with their own external access and no residential links between them – each section may be assessed as a separate building against the thresholds.
New buildings are slightly different
During design and construction, the definition also includes hospitals and care homes of 18m or 7 storeys. New HRBs go through the regulator's gateway regime – see Gateway 2 rejections. Planning Gateway One uses a related but separate test: see Planning Gateway One fire statements.
What follows if your building is in scope
- Registration with the Building Safety Regulator. It's an offence to allow an unregistered HRB to be occupied.
- Key building information submitted after registration (the regulations set a 28-day window).
- A principal accountable person and any other accountable persons identified – see responsible person vs accountable person.
- An assessment of building safety risks – fire spread and structural failure – and reasonable steps to manage them.
- A safety case report, and a building assessment certificate application when the regulator directs – see why safety cases get refused.
- A mandatory occurrence reporting system, a resident engagement strategy and the golden thread of information.
- The Fire Safety (England) Regulations 2022 duties for high-rise residential buildings, such as the premises information box, and the residential PEEPs duties.
Borderline cases
Buildings close to 18 metres, with sloping sites, roof-level accommodation or several connected blocks are often borderline. Getting it wrong either way is costly – unnecessary compliance spend, or offences for failing to register. Our Building Safety Act support includes measured height checks and written advice you can rely on.
Worked examples
- A 6-storey block of flats, 19m to the top floor surface. Fewer than 7 storeys, but over 18m – it's a higher-risk building.
- An 8-storey block where one storey is a basement. The basement is ignored, leaving 7 storeys – still in scope, whatever the height.
- A 7-storey block where the top storey is only plant rooms. The plant storey is ignored, leaving 6 storeys; whether it's in scope then depends on the height of the top occupied floor.
- A 20m hotel with two staff flats on the top floor. Not wholly a hotel, and it has two residential units – likely in scope. Take advice on borderline mixed-use cases.
- A 10-storey student hall. Student accommodation isn't excluded – in scope. See PBSA fire safety.
How we can help
We match each project to a qualified specialist and confirm the scope, the named professional and a fixed fee before you commit.
Sources
- GOV.UK – Criteria for being a higher-risk building during the occupation phase
- GOV.UK – Criteria for whether a new building being designed and constructed is a higher-risk building
This guide is general information based on the law and guidance in England as at 8 November 2026. It isn't legal advice – for advice on a specific building, get in touch.