Definition of a Higher-Risk Building for the purposes of the Building Safety Act 2022.

Current official guidance makes the following distinction between a general definition of a Higher-Risk Building, and a Higher-Risk Building in occupation.

1. Higher-risk building is the technical term for buildings within the scope of the higher-risk regime.

2. Higher-risk building in-occupation refers to buildings which are in scope of the requirements of Part 4 of the Building Safety Act.

The Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 [The Regulation] completed the legal definition of higher-risk building. They Regulation came into force on 6th April 2023.

A Higher-Risk building is defined as a building with at least two residential units, which are at least 18 metres in height, or have at least seven storeys.

Further refinement of the definition is made by the Building Safety Regulator to explain when buildings with two or more qualifying towers may be viewed as a single High-Rise Building for registration purposes.

Section 5 of the Regulation define how the height of the building can be measured.

5.(1) Subject to paragraph (2), the height of a building is to be measured from ground level to the top of the floor surface of the top storey of the building (ignoring any storey which is a roof-top machinery or roof-top plant area or consists exclusively of roof-top machinery or roof-top plant rooms).

5.(2) Where the top storey is not directly above the lowest part of the surface of the ground adjacent to the building, the height of the building is to be measured vertically from the lowest part of the surface of the ground adjacent to the building to the point which is a horizontal projection from the top of the floor surface of the top storey of the building (ignoring any storey which is a roof-top machinery or roof-top plant area or consists exclusively of roof-top machinery or roof-top plant rooms).

Section 6 of the Regulation defines what is to be included and excluded as being a storey.

6.1 Subject to paragraph 6.2, when determining the number of storeys a building has, the following is to be ignored:

• any storey which is below ground level;
• any storey which is a roof-top machinery or roof-top plant area or consists exclusively of roof-top machinery or roof-top plant rooms; and
• any storey consisting of a gallery with an internal floor area that is less than 50% of the internal floor area of the largest storey vertically above or below it, which is not below ground level.

6.2 Any storey directly beneath the building which is not below ground level is to be counted in determining the number of storeys the building has.

6.3 A storey is treated as below ground level if any part of the finished surface of the ceiling of the storey is below the ground level immediately adjacent to that part of the building.

The Regulation exclude the following from being a Higher-Risk Building:

• a building that contains living accommodation provided by the Ministry of Defence (either alone or in combination with other accommodation);
• a care home;
• a hospital;
• a secure residential institution;
• a hotel; or
• military barracks;
• a building that contains living accommodation provided by the Ministry of Defence (either alone or in combination with other accommodation;
• a building that contains living accommodation (either alone or in combination with other accommodation) for:
• His Majesty’s forces;
• any visiting force or an international headquarters or defence organisation designated for the purposes of the International Headquarters and Defence Organisations Act 1964.

The definition of higher-risk building is only for the purpose of the new higher-risk regime. The definitions in the Act and Regulations do not amend definitions in other legislation or definitions of building in other parts of the Act, such as the definition of “relevant building” under section 117 of the Act which defines a ‘relevant building’ for the purpose of the leaseholder protections under sections 119 to 125 and Schedule 8 of the Act.