What is a higher-risk building? The two definitions, kept separate
Higher-risk building (HRB) sounds like one definition. It isn't. The Building Safety Act runs two regimes — one for buildings in occupation, one for buildings being designed and constructed — and they define an HRB differently. Using the wrong one is the most common mistake, so this page keeps them apart.
In occupation
An occupied building in England is a higher-risk building if it is at least 18 metres in height or has at least 7 storeys, and contains at least 2 residential units.
- How height is measured: to the top of the floor surface of the top storey; rooftop machinery and plant areas are excluded; on sloping ground, measured from the lowest part of the ground.
- How storeys are counted: exclude storeys below ground, storeys that are only rooftop plant or machinery, and gallery floors smaller than half the adjacent storey's area.
- Excluded uses: a building used entirely as a hospital, care home, secure residential institution, hotel or military barracks is not an in-occupation higher-risk building.
- Residential unit: a dwelling or any other unit of living accommodation — flats, studio flats, student accommodation, supported housing.
Legal duty — Building Safety Act 2022, s65 · Measurement — Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 · BSR guidance, occupation-phase criteria
In design & construction
For a new building being designed or constructed, the threshold is the same — at least 18 metres or at least 7 storeys — but the qualifying uses are wider: a building with at least 2 residential units, or a care home, or a hospital.
Work to an existing building — including changes of use or adding storeys — has separate BSR guidance and additional building-definition considerations. This summary covers the new-building test; check the existing-building criteria separately.
- Key difference: care homes and hospitals are higher-risk buildings for design and construction, but not for the occupation regime.
- Cannot split: during design and construction, attached structures are treated as a single higher-risk building — you cannot split it by individual component thresholds. The occupation regime allows independent sections in defined cases.
Descriptions — Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 · Procedures — Building (Higher-Risk Buildings Procedures) (England) Regulations 2023 · BSR guidance, design-and-construction criteria
Occupation vs design & construction, side by side
| In occupation | Design & construction | |
|---|---|---|
| Height / storeys | ≥18m or ≥7 storeys | ≥18m or ≥7 storeys |
| Residential units | ≥2 required | ≥2, or a care home, or a hospital |
| Hospitals / care homes | Excluded | Included |
| Excluded uses | hospital, care home, secure residential, hotel, barracks | secure residential, hotel, barracks |
| Attached structures | may be independent sections | single building (cannot split) |
| Regime | BSA 2022 Part 4 | building-control regime (Gateways) |
Try the higher-risk building checker, read the accountable person's duties, or go back to Building Safety Act compliance.
Higher-risk buildings — FAQs
Does a care home ever count as a higher-risk building?
Yes, but only in the design and construction regime. A care home meeting the height or storey threshold is a higher-risk building for design and construction. It is not a higher-risk building under the in-occupation regime, which is limited to buildings with at least 2 residential units.
Is it 18 metres or 7 storeys — and, or?
Either one meets the height/storey limb: a building at least 18 metres tall or with at least 7 storeys qualifies on that limb. You still need the use limb as well (residential units, or — in design and construction — a care home or hospital).
Does this definition apply in Wales?
No. Wales has its own separate regulations for higher-risk buildings. This page is about the England regime.