Most of the Building Safety Act's strictest duties hang on one question: is this a higher-risk building? The answer comes down to two thresholds, 18 metres and 7 storeys, and a precise way of measuring them. Here's the definition, how to measure, and which buildings are left out, summarised from GOV.UK guidance.
Before you rely on this: it's a plain-English summary of GOV.UK guidance on the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 as it stood in October 2026, and it applies to England. It isn't legal advice. If a building is close to a threshold, check the official guidance and its diagrams, listed at the end.
The higher-risk building definition at a glance
| Question | In short |
|---|---|
| Height test | At least 18 metres high, or at least 7 storeys. It only has to meet one of the two |
| Use test, once occupied | Contains at least 2 residential units |
| Excluded once occupied | Buildings used entirely as a hospital, care home, secure residential institution, hotel or military barracks, and buildings with Ministry of Defence living accommodation |
| During design and construction | Also includes hospitals and care homes that meet the height test |
| How height is measured | From ground level to the top of the floor surface of the top storey, ignoring roof-top plant |
| Where it applies | England |
The definition in the Act
Section 65 of the Building Safety Act 2022 defines a higher-risk building, for the part of the Act that covers occupied buildings, as a building in England that:
- is at least 18 metres in height or has at least 7 storeys, and
- contains at least 2 residential units.
The height test is either-or. GOV.UK's guidance gives the example that a building of 17 metres and 6 storeys meets neither threshold, so it isn't a higher-risk building whatever it's used for. A building of 7 storeys that meets the use test is one, without needing to be measured for height.
Which buildings are excluded
Once a building is occupied, it's excluded from this part of the regime if the entire building is used as a hospital, care home, secure residential institution, hotel or military barracks, or if it contains any living accommodation provided by the Ministry of Defence for military personnel.
The rules for buildings being designed and built are slightly different. During design and construction, a building that meets the height test is a higher-risk building if it contains at least 2 residential units, or is or contains a hospital or a care home. That's why hospitals and care homes go through the Building Safety Act gateways but aren't covered by the occupation duties.
How to measure the height
The 2023 Regulations set the method. Height is measured from ground level to the top of the floor surface of the top storey, not to the roof. Two details matter:
- Ground level. On flat ground, it's the surface of the ground immediately next to the building. On sloping or uneven ground, it's the lowest part of the ground next to the building.
- Roof-top plant. A top storey that is only roof-top machinery or plant rooms is ignored, so you measure to the floor of the storey below it.
How to count the storeys
Storeys are counted from the storey at ground level up to the top storey. The Regulations say to ignore:
- any storey below ground level. A storey counts as below ground if any part of its finished ceiling is below the adjacent ground level
- any storey that is only roof-top machinery or plant rooms
- a gallery whose internal floor area is less than half that of the largest storey above or below it.
The guidance adds that a storey must be fully enclosed to count. An open roof, such as a roof garden, isn't a storey. And only roof-top plant is ignored: a plant room floor in the middle of a building still counts as a storey.
What it means if your building is one
For an occupied higher-risk building with residential units, the duties fall on the accountable persons, led by the principal accountable person. Among other things, the building must be registered with the Building Safety Regulator before anyone lives there, with its key building information. The principal accountable person prepares a safety case report, and the building's information is kept as the golden thread. For the whole picture, there's a plain-English summary of the Building Safety Act.
Where Building Search fits
Answering "is this a higher-risk building?" usually means finding drawings, sections and survey records for the building. Building Search makes a building's documents searchable and answers a plain question with the document and exact page the answer came from. It doesn't decide whether a building is in scope, so check borderline cases against the official guidance. You can try the interactive demo, which uses fictional sample data.
Looking after several buildings' files? I'll send you a free one-page plan showing what a search page for one of your buildings would look like and what it would cost. See how Building Search works.
Questions people actually ask
What is a higher-risk building?
Under the Building Safety Act, an occupied building in England that is at least 18 metres high or has at least 7 storeys, and contains at least 2 residential units. Some buildings are excluded, such as those used entirely as hotels, hospitals or care homes.
How do you measure the height of a higher-risk building?
From ground level to the top of the floor surface of the top storey, ignoring any top storey that is only roof-top plant. On sloping ground, measure from the lowest part of the ground next to the building.
Does a building have to be both 18 metres and 7 storeys?
No. It only has to meet one of the two thresholds, as well as the use test.
Do basements count as storeys?
No. Any storey below ground level is ignored, and a storey counts as below ground if any part of its finished ceiling is below the adjacent ground level.
Are hotels higher-risk buildings?
Not for the occupation part of the regime. Buildings used entirely as a hotel are excluded, as are hospitals, care homes, secure residential institutions and military barracks.
