Higher-risk buildings explained

What is a higher-risk building?

In England, a higher-risk building during design and construction is at least 18 metres high or has at least 7 storeys, and contains at least two residential units or is a hospital or care home. Once occupied, only the residential buildings stay in the regime; hospitals and care homes drop out of the occupation-phase rules.

The definition decides who the building control body is, what must be submitted before work starts, and how much the project team has to document. If a scheme is a higher-risk building (HRB), building control approval comes from the Building Safety Regulator (BSR) through the gateway process, not from a local authority or a registered building control approver.

The legal definition is in section 120D of the Building Act 1984 for design and construction, and section 65 of the Building Safety Act 2022 for occupation. Both are supplemented by the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 (SI 2023/275), which set out which uses qualify, how height and storeys are measured, and what is excluded.

The government reviewed the definition after the Grenfell Tower Inquiry Phase 2 report recommended an urgent review. In its response of 17 December 2025 it accepted the BSR's finding that there was insufficient evidence to change the definition at that time, and committed to keeping it under continuous review. Any change would need consultation and Parliamentary approval. As of October 2026 it has not changed.

The size and use tests

A building is an HRB during design and construction if it meets one size test and one use test, and is not excluded. Height and storeys are alternatives; so are the three qualifying uses.

Under regulation 2 of SI 2023/275, a residential unit is a dwelling or any other unit of living accommodation. Government guidance gives flats, studios, houses in multiple occupation, university hall rooms with shared facilities and supported accommodation units as examples. Serviced apartments count. Short-term lets count. A hospital means one with at least one bed for overnight admission, and a care home takes the meaning in the Care Standards Act 2000.

Mixed-use and attached buildings

A mixed-use building qualifies if it meets the height or storey test and contains a qualifying use, so a shopping centre with two or more flats above it can be an HRB. During design and construction, attached structures are treated as one building, even if some parts would not meet the thresholds on their own. Government guidance gives the example of a 4-storey block attached to an 8-storey block on a slope: the whole is measured together and counts as 8 storeys. Independent sections can only be assessed separately for the occupation phase.

What is excluded?

Regulation 7 of SI 2023/275 excludes buildings that consist wholly of a secure residential institution, a hotel, or military barracks and armed forces living accommodation. The word "wholly" does the work: a mixed building is assessed on its qualifying parts.

Government guidance says hostels offering overnight stays for leisure or business are treated as hotels, but hostel-style supported accommodation is not. A building that combines a hotel with two or more residential units, such as serviced apartments, can be an HRB if it meets the height or storey test.

How height and storeys are measured

Regulation 5 of SI 2023/275 measures height from ground level to the top of the floor surface of the top storey, not to the roof or parapet. Regulation 6 sets out which storeys are ignored when counting to seven.

• Storeys consisting only of roof-top machinery or plant are ignored.
• Ground level is the level of the ground immediately adjacent to the building if it is uniform. If it is not, it is the lowest part of the adjacent ground.
• If the top storey is not directly above that lowest point, height is measured vertically from that point to a horizontal projection of the top floor surface.

Which storeys are ignored?

• Storeys below ground level, meaning any storey where any part of the finished ceiling is below the adjacent ground level. Basements therefore do not count.
• Storeys consisting only of roof-top plant or machinery.
• Galleries whose floor area is less than 50% of the internal floor area of the largest storey vertically adjacent to them.

Do roof gardens count as a storey?

The government's position, in guidance last updated on 28 May 2025, is that open roof gardens are not storeys. A First-tier Tribunal decision of 3 July 2024 took a different view, and the government has said it is consulting on amending the regulations to make its position explicit. Until any amendment is made, schemes with accessible roof terraces close to the threshold deserve early advice.

Height is measured to the top storey floor from the lowest adjacent ground, not to the parapet from the street.

What changes for architects on a higher-risk building

An HRB moves building control to the BSR, adds approval gateways before work starts and before occupation, and controls changes in between. The practical effect is that design information has to be complete earlier, and the record has to be kept throughout.

Planning gateway one

For planning applications made since 1 August 2021, schemes involving a "relevant building" (18 metres or 7 storeys, with two or more dwellings or educational accommodation) need a fire statement, and the Health and Safety Executive is a statutory consultee. The relevant-building test is close to the HRB test but not identical, so check both.

Gateway 2

The BSR must approve a building control approval application before any work starts. Under regulation 5 of the Building (Higher-Risk Buildings Procedures) (England) Regulations 2023, the statutory period is 12 weeks for a new HRB, extendable by agreement. The application includes a Building Regulations compliance statement, a fire and emergency file, and construction control, change control and mandatory occurrence reporting plans.

Dutyholders

The client must appoint the Building Regulations principal designer and principal contractor before the Gateway 2 application is submitted, and keep written records of how their competence was checked.

Design information

The BSR can refuse an application that is not detailed enough to show compliance. This pushes design resolution on fire, structure and external walls earlier than many teams are used to. Specifications have to agree with the fire strategy and drawings.

Change control

The BSR lists changes to external walls, structure, escape routes, number of storeys or units, and replacing a product with one of lower reaction-to-fire performance as major changes that need approval before related work starts.

Gateway 3

A completion certificate from the BSR is needed before a residential HRB can be registered and occupied. The application relies on an up-to-date set of agreed documents, a change control log and signed declarations.

Approved Document B height triggers are separate

Approved Document B has its own height-based provisions for residential buildings, and they are not measured in exactly the same way as the HRB test. Check each provision against the method in the current edition of the Approved Document rather than assuming the HRB measurement applies.

What about Wales and Scotland?

The BSR regime described here applies in England. Wales brought its own higher-risk building design and construction regime into force on 1 July 2026, with a wider definition.

Under the Building Safety (Description of Higher-Risk Building) (Design and Construction Phase) (Wales) Regulations 2023, a building of at least 18 metres or 7 storeys qualifies with just one residential unit, and children's homes are included alongside hospitals and care homes. Scotland has its own building standards system.

• ✓Confirm the jurisdiction: England, Wales or Scotland.
• ✓Measure height from the lowest adjacent ground to the top storey floor, ignoring plant-only storeys.
• ✓Count storeys, excluding basements, plant-only storeys and small galleries; take advice on roof terraces near the threshold.
• ✓Treat attached structures as one building during design and construction.
• ✓Count residential units (two in England, one in Wales) and check for hospital, care home or excluded uses.

Where Avoice fits

Whether a scheme is an HRB turns on a few precise definitions spread across an Act, two sets of regulations and government guidance. Most errors come from measuring height the wrong way or missing an attached structure.

The Avoice Regulations library brings together the Building Safety Act regime, the Building Regulations 2010 and the Approved Documents in one searchable place, with AI answers that say whether they come from legislation or statutory guidance. It is useful for quick checks such as how height is measured or what counts as a storey. For live projects, the Building Regs Tracker and Golden Thread export in the Compliance module keep the evidence trail an HRB needs.

Software can retrieve, compare and flag. The client, the principal designer and the BSR still decide whether a building is in scope and whether the evidence is adequate.