Criteria for determining whether an existing building is a higher-risk building during building work
Source: gov.uk (2025-05-28)

This guidance relates to the legal criteria for determining whether a building is considered a higher-risk building under the Building Safety Act 2022 and the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023. It relates to the definition of higher-risk building during building work in an existing building only.

Following the initial statement (https://buildingsafety.campaign.gov.uk/building-safety-regulator-making-buildings-safer/building-safety-regulator-news/mhclg-and-bsr-reviewing-first-tier-tribunal-on-classification-of-roof-gardens/) dated 18 October 2024, the Ministry of Housing, Communities and Local Government has carefully considered the views expressed by the Tribunal in the First-tier Tribunal decision (https://www.gov.uk/residential-property-tribunal-decisions/smoke-house-and-curing-house-18-remus-road-london-e3-2nf-lon-slash-00bg-slash-hyi-slash-2023-slash-0024) dated 3 July 2024.

The department recognises the need to provide clarity within the legislation. We are consulting the Building Safety Regulator and other relevant stakeholders on a proposal to amend the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 to make it clear that roof gardens should not be considered a storey when determining whether a building is a higher-risk building under section 120D of the Building Act 1984 and section 65 of the Building Safety Act 2022.

In the meantime, the department’s view remains that roof gardens are not storeys for these purposes. This is the basis for current government guidance (https://www.gov.uk/government/collections/guidance-on-the-criteria-for-being-a-higher-risk-building), which the sector and regulatory bodies should continue to refer to.

Introduction

This guidance sets out the criteria for a building to be considered a higher-risk building during building work in an existing higher-risk building. This includes building work to an existing building which will make it a higher-risk building (for example adding storeys) or for a building undergoing a change of use. Higher-risk buildings are subject to the requirements of the new higher-risk regime directly overseen by the Building Safety Regulator (the Regulator).

Higher-risk buildings during building work in an existing building are defined in Section 120D of the Building Act 1984 (the 1984 Act) as amended by the Building Safety Act 2022 (the 2022 Act) and Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 (the Regulations).

To understand whether an existing building during building work is a higher-risk building, the 1984 Act as amended by the 2022 Act, and the Regulations need to be considered together.

During building work in an existing building, higher-risk buildings are defined as buildings with at least two residential units, care homes, and hospitals which are at least 18 metres in height or have at least 7 storeys. This definition does not amend definitions of higher-risk buildings in other legislation - for example, the definition for higher-risk buildings in occupation (section 65 of the 2022 Act), which can be found in the Criteria for being a higher-risk building during the occupation phase of the new higher-risk regime (https://www.gov.uk/guidance/criteria-for-being-a-higher-risk-building-during-the-occupation-phase-of-the-new-higher-risk-regime). Sections 119 to 125 and Schedule 8 of the 2022 Act define “relevant building” for the purpose of leaseholder protections.

This guidance document includes the relevant text from the 1984 Act as amended by the 2022 Act and from the Regulations with explanations and diagrams. It is a tool to help potential dutyholders (i.e., the client, designer, principal designer, contractor, and principal contractor) and accountable persons determine if their building is a higher-risk building. This guidance should be used over other guidance covering buildings, height measurements and/or storey measurements to determine whether the definition of higher-risk building set out is law applies to your building. This guidance and the specific circumstances of your building need to be considered by you when discharging your duties under building regulations.

In addition to becoming a higher-risk building under the Act and the Regulations, your building may also be subject to other legislation and statutory duties, such as the Regulatory Reform (Fire Safety) Order 2005. You will need to work with the relevant dutyholders in the building to ensure it is safe.

Diagrams in this guidance document show examples of potential buildings and are for illustrative purposes only. You will need to consider the legislation carefully to understand whether you are responsible for a higher-risk building in scope of the higher-risk regime. You may wish to seek legal advice on this.

The definitions of key terms in this guidance can be found in the Glossary.

Guidance for understanding whether your building is a higher-risk building during building work in an existing building

Key criteria to consider when determining if a building is higher-risk includes:

1. Use criteria: What is my building used for? Does it meet any of the included or excluded categories of building?

2. Legal definition of building: How does the building definition in Regulations apply to my building structure?

3. Height and storeys: How do the methods for measuring height and storeys in the Regulations apply to my building? Does my building meet either the 18-metre or 7-storey height threshold when measured using these methods?

You will need to consider all 3 criteria.

Use criteria

To be considered a higher-risk building during building work in an existing building, a building must meet a certain set of use criteria. This is in addition to meeting the height or storeys threshold.

If a building meets the height or storeys threshold and contains at least two residential units, is or contains a hospital or a care home, then it is a higher-risk building. This applies unless the entire building is used as a secure residential institution, hotel, or military barracks, or if the building contains any living accommodation provided by the Ministry of Defence for military personnel. These buildings are explicitly excluded.

Use criteria for buildings during building work in an existing building under the Building Act 1984 and the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023

Section 120D of the Building Act 1984 sets out the buildings which are included in the design and construction part of the higher-risk regime.

120D. Meaning of “higher-risk building” etc

(2) “Higher-risk building” means a building in England that—

(a) is at least 18 metres in height or has at least 7 storeys, and

(b) is of a description specified in regulations made by the Secretary of State.

Regulation 2 of the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 sets out the buildings which are included in the design and construction part of the higher-risk regime.

2. Specified descriptions of building under section 120D of the Building Act 1984

(2) The following descriptions of building are specified for the purposes of section 120D(2)(b) of the 1984 Act—

(a) a building which contains at least two residential units;

(b) a care home;

(c) a hospital.

Regulation 7 sets out the buildings which are excluded from the design and construction part of the higher-risk regime.

7. (1) For the purposes of section 120D of the 1984 Act a “higher-risk building” does not include a building of a description specified in paragraph (2).

(2) The following descriptions of building are specified for the purposes of paragraph (1)

(a) a building that comprises entirely of—

(i) a secure residential institution;

(ii) a hotel;

(iii) military barracks;

(b) a building that contains living accommodation provided by the Ministry of Defence (either alone or in combination with other accommodation);

(c) a building that contains living accommodation (either alone or in combination with other accommodation) for—

(i) His Majesty’s forces;

(ii) any visiting force or an international headquarters or defence organisation designated for the purposes of the International Headquarters and Defence Organisations Act 1964.

This means that buildings proposed to be mixed-use buildings are subject to the requirements of the higher-risk regime. For example, if a building contains a shopping centre but also has two or more residential units, then it is a higher-risk building, provided it meets the height or storeys threshold. Buildings which are boarding accommodation in schools and university accommodation would also be considered higher-risk buildings, provided they meet the height or storeys threshold for a higher-risk building, as they contain residential units.

Buildings that contain supported and sheltered accommodation are considered higher-risk buildings if they meet the height or storeys threshold, as they contain residential units. Examples of supported and sheltered accommodation which could fall under the higher-risk regime include domestic abuse refuges, children’s homes and supported or sheltered homes for older people and those with additional care needs.

Residential unit

A residential unit is a dwelling or any other unit of living accommodation and is defined in the Regulations.

Examples of a residential unit are a flat, a studio flat, a home of multiple occupation, shared accommodation within university halls (e.g. a bedroom with shared kitchen and bathroom) or a unit within a supported accommodation building.

A residential unit can be found within any type of building and could have any tenure. Privately owned, private rented and social rented units are all considered residential units under the higher-risk regime.

Care homes and hospitals

Care homes provide accommodation, together with nursing or personal care, for those who are or have been ill, mentally unwell, or dependent on alcohol or drugs or who are disabled or infirm.

Hospitals are institutions for receiving and treating those who are ill, convalescing or need medical rehabilitation, or a maternity home.

Buildings used for receiving and treating those who are ill, convalescing or need medical rehabilitation, or a maternity home without at least one bed for an overnight stay are not considered hospitals under the higher-risk regime. For example, a general practitioner surgery which does not allow overnight stays would not meet the definition of a hospital.

Exclusions

Secure residential institutions

Buildings used entirely as secure residential institutions are excluded from the higher-risk regime. Secure residential institutions include prisons, young offenders’ institutions, detention centres, secure training centres, custody centres, short-term holding centres and secure local authority accommodation. If a proposed building is used entirely for one of these purposes, then it is not a higher-risk building.

Hotels and other serviced accommodation

Buildings used entirely as hotels are excluded from the higher-risk regime. Hotels are buildings which provide overnight accommodation for customers who stay for the purpose of leisure or business.

We consider hostels which also provide overnight accommodation to customers for leisure or business as a type of hotel and so if a building is used entirely as a hostel, then it is not considered a higher-risk building. Hotels are excluded regardless of how long these buildings are occupied by individuals or groups of customers.

Serviced apartments do not fall within the meaning of hotel and are considered higher-risk buildings if they meet the height or storeys threshold.

A short-term let (for example, a short-term rental property let online) is considered a residential unit. If there was another residential unit within the building and the height or storeys threshold was met then the entire building, including the short-term let property, would be considered a higher-risk building.

Military premises

Buildings used exclusively as military barracks are excluded from the higher-risk regime.

Buildings which contain any living accommodation either for His Majesty’s forces, any visiting forces or an international headquarters or defence organisation are also excluded.

Building definition

Building for the purposes of the higher-risk regime is defined in regulation 4 of the Regulations. The diagrams in this section will help you determine how regulation 4 applies to your building.

Legal definition of a building in the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023

Regulation 4 sets out the definition of a building.

(1) Subject to paragraph (2), where a structure is not attached to any other structure, that structure is a “building”.

(2) Subject to paragraph (5), where a structure that is not attached to any other structure contains one or more independent sections, each independent section is a “building”.

(3) Subject to paragraph (4), where two or more structures are attached, that set of structures are a “building”.

(4) Subject to paragraph (5), where two or more structures that are attached contains one or more independent sections, each independent section is a “building”.

(5) Paragraphs (2) and (4) do not apply while a building is being constructed or proposed to be constructed.

(6) An “independent section” is a section that—

a. has access, which can be reached from anywhere in the section, for persons to enter and exit the wider building; and

b. either—

i. has no access to any other section of the wider building; or

ii. only has access to another section of the wider building which does not contain a residential unit.

(7) “Access” means a doorway, archway or similar opening but does not include a doorway, archway or similar opening intended for exceptional use including emergency use or use for the purpose of maintenance.

(8) The “wider building” means—

a. in relation to a section of a structure that is not attached to any other structure, that structure;

b. in relation to a section within two or more structures that are attached, that set of structures.

(9) Where a section is a “building” pursuant to paragraphs (2) or (4), any plant room containing equipment for the provision of services to that section is to be considered as part of that building.

The building definition addresses both single structures and multiple structures which are connected. For certain, more complex, structures the definition allows part (“independent section” in the Regulations) of an overall structure (“wider building” in the Regulations) to be considered as the ‘building’ for the purposes of the higher-risk regime.

For an overall structure to contain independent sections, not every part needs to meet the independent section criteria. Provided the part of the overall structure you are assessing meets the criteria to be an independent section, it is an independent section, and, therefore, its own building. You will then need to assess whether it is also a higher-risk building against the height or storeys threshold and use criteria.

To help assess whether part of an overall structure you are responsible for can be considered an independent section, you should consider whether that section:

1. has its own entrance and exit to the outside, accessible from anywhere within that section

and;

2. either

a. has no access to any other section within the overall structure

or;

b. only has access to another section of the overall structure which does not contain a residential unit.

The key terms (overall structure, access, residential unit and section) from the criteria are defined in the glossary.

Example buildings defined under the building definition

Diagrams 1 – 7 set out examples of different building types and how they should be considered under the definition in the Regulations. These examples are included to help you assess your building; however, they are illustrative examples and do not represent all building types.

Diagram 1 shows one 7-storey residential tower (tower 1A). Tower 1A is:
- not attached to any other structure; and
- does not have anything within the overall structure which could be considered an independent section.
Tower 1A is one building.

Diagram 2 shows one 7-storey residential tower (tower 2A) with a separated gym on the ground floor (section 2B). Tower 2A has:
- its own entrance and exit to the outside, accessible from anywhere within tower A; and
- no access to another section within the overall structure.
Tower 2A (excluding section 2B) is an independent section and considered a ‘building’ for the higher-risk regime.

Diagram 3 shows one 7-storey residential tower (tower 3A) with a function room / commercial cafe on the 6th floor of the tower (area 3B). Tower 3A has:
- its own entrance and exit to the outside, accessible from anywhere within tower 3A; and
- no access to any other section of the overall structure. Although tower 3A has access to area 3B, area 3B cannot reasonably be considered a separate section as it relies on tower 3A for egress.
As there are no independent sections in this building tower 3A and area 3B are considered one building.

Diagram 4 shows two 7-storey residential towers (tower 4A and tower 4B) attached by a party wall and basement car park. Tower 4A has:
- its own entrance and exit to the outside, accessible from anywhere within tower 4A; and
- access to another section within the overall structure which does not contain a residential unit (the basement carpark).
Tower 4A is an independent section and considered a ‘building’ for the higher-risk regime.

The same assessment applies to tower 4B; it is an independent section and considered a ‘building’ for the higher-risk regime.

Diagram 5 shows two 7-storey residential towers (tower 5A and tower 5B) attached by a party wall, with access to move between them and a third 7-storey residential tower (tower 5C) attached to tower 5B via walkways. Tower 5A has:
- access to another section within the overall structure which contains a residential unit (tower 5B).
Tower 5B has:
- access to another section (in this case two sections) within the overall structure which contains a residential unit (tower 5A and tower 5C).
Tower 5C has:
- access to another section within the overall structure which contains a residential unit (tower 5B). This is because the walkways attaching tower 5B and tower 5C cannot be considered separate sections as they do not have their own egress outside.
Towers 5A, 5B and 5C cannot be considered independent sections, therefore the overall structure is considered a ‘building’ for the higher-risk regime.

Diagram 6 shows one 7-storey residential tower (tower 6A) and one 5-storey residential tower (tower 6B) attached by a shared basement carpark and a second 7-storey residential tower (tower 6C) attached to tower 6B via a walkway. Tower 6A has:
- its own entrance and exit to the outside, accessible from anywhere within tower 6A; and
- access to another section within the overall structure which does not contain a residential unit (the basement carpark).
Tower 6A is an independent section and considered a ‘building’ for the higher-risk regime.

Tower 6B has:
- its own entrance and exit to the outside, accessible from anywhere within tower 6B; and
- access to another section within the overall structure which does not contain a residential unit (the basement carpark and the walkway). The basement and walkway can be considered sections as they are used for a different purpose than the towers and have their own egress outside.
Tower 6B is an independent section and considered a ‘building’ for the higher-risk regime, however, as tower 6B does not meet the storey threshold it is not a higher-risk building (see section on measuring height and counting storeys for more detail on height thresholds).

Tower 6C has:
- its own entrance and exit to the outside, accessible from anywhere within tower 6C; and
- access to another section within the overall structure which does not contain a residential unit (the walkway). The walkway can be considered a section as it is used for a different purpose than the towers and has its own egress outside.
Tower 6C is an independent section and considered a ‘building’ for the higher-risk regime.

Diagram 7 shows four 7-storey residential towers on a shared podium. Tower 7A and tower 7B are attached by a party wall, with maintenance access between them. Tower 7C and tower 7D are attached by a party wall, with access regularly used by residents between them. Tower 7A has:
- its own entrance and exit to the outside, accessible from anywhere within tower 7A;
- access to another section within the overall structure which does not contain a residential unit (the podium containing shops). The shops and podium can be considered their own section as they are used for a different purpose than the residential towers and have their own egress outside, therefore they are not part of the independent section; and
- a doorway from tower 7A to another section (tower 7B) within the overall structure used solely for maintenance and not for regular use. This is not considered as doorway access to another section.
Tower 7A is an independent section and considered a ‘building’ for the higher-risk regime.

The same assessment applies to tower 7B; it is an independent section and considered a ‘building’ for the higher-risk regime.

Tower 7C has:
- its own entrance and exit to the outside, accessible from anywhere within tower C;
- access to another section within the overall structure which contains a residential unit (tower 7D); and
- no access to the podium containing shops. The podium can be considered its own section and it is used for a different purpose than the residential towers and has its own egress outside
The same assessment applies to tower 7D.

Tower 7C and tower 7D are not individually independent sections because there is access between the residential areas. Together, towers 7C and 7D are an independent section and therefore a ’building’ for the higher-risk regime.

Plant rooms

Plant rooms are areas which contain machinery or equipment that provide services to one or more buildings.

Areas such as bin stores are not considered plant rooms. Substations which are not in buildings are also not considered plant rooms.

Where a building has independent sections, any plant room containing equipment for the provision of services to that independent section should be considered as part of that building. A plant room may be considered part of more than one independent section. This applies regardless of where the plant room is within the overall structure. Only the plant room should be considered part of the building, not the entire area in which the plant room sits.

Plant rooms fall under the definition of common parts. The accountable person for the plant room will therefore be the accountable person who holds the legal estate in possession or has the repairing obligation for that plant room. Where there are multiple accountable persons involved in a building with independent sections, they must cooperate with each other to manage the building safety risks in relation to that plant room.

Counting storeys and measuring height

For a building to be a higher-risk building it will meet either the height or storeys threshold – it does not need to meet both (although it may). The height threshold is set at 18 metres or higher. The storeys threshold is set at 7 storeys or more.

If a building meets the 7-storey threshold and meets the use criteria set out in this guidance, this it is a higher-risk building and does not need to be measured against the height threshold. If a building is 18-metre in height and meets the use criteria, then it is a higher-risk building and does not need to meet the storeys threshold.

If a building does not meet either of the 18-metre or 7-storey height thresholds (for example, it is 17 metres and six storeys in height), then it is not a higher-risk building, regardless of whether it meets the use criteria.

Prescribed method for measuring height and counting storeys in the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023

Regulation 5 sets out the method for measuring height.

(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).

(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).

Regulation 6 sets out the method for counting storeys.

6. — (1) Subject to paragraph (2), when determining the number of storeys a building has the following is to be ignored—

(a) any storey which is below ground level;

(b) 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

(c) 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.

(2) Where a section is a building pursuant to regulation 4(2) or (4), 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.

(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.

Regulation 1(3) defines ground level for these Regulations.

“ground level”, in relation to a building, means—

(a) where the level of the surface of the ground on which the building is situated is uniform, the level of the surface of the ground immediately adjacent to the building; or

(b) where the level of the surface of the ground on which the building is situated is not uniform, the level of the lowest part of the surface of the ground adjacent to the building.

Storeys should be counted from the storey at ground level to the top storey. Height should be measured from ground level to the top of the floor surface of the top storey of the building. The method set out in this guidance should be used when determining whether your proposed building is a higher-risk building, rather than methods set out in other documents.

Ground level

When counting storeys and measuring height you should measure from ground level. You will need to carefully consider where ground level is for your building. There may be situations in which small spaces have been created adjacent to the building below the level of normal ground floor access such as lightwells. It is unlikely to be appropriate to consider such areas for the purpose of identifying ground level.

If the building being measured sits on uniform flat ground, then ground level is the surface of the ground which is directly adjacent to the building. This is demonstrated in Diagram 8.

When counting storeys, any storeys which are below ground level should not be counted. A storey is considered below ground level and should not be counted if any part of the storey’s finished ceiling is below ground level for the building. Similarly, when measuring height, parts of the building which are below ground level are not measured. Measurements always start from the ground level. This is demonstrated in Diagram 8.

Diagram 8 shows a 7-storey residential tower on flat ground.

For the type of building shown in Diagram 8, storeys should be measured from the first storey above ground level, as indicated by the arrow on the left. The storey below ground level should not be counted. Height should be measured from ground level to the floor surface of the top storey, as indicated by the arrow on the right.

For the building shown in Diagram 8, based on the method for counting storeys in the Regulations, this structure would have 7 storeys.

When counting storeys and measuring height, if the building being measured sits on uneven ground (for example, a sloping area), then ground level is the lowest part of the ground which touches the building. This is demonstrated in Diagram 9.

Diagram 9 shows a 7-storey residential tower on sloped ground.

In this example, based on the method for counting storeys in the Regulations, this structure would have 7 storeys. If you have assessed that your structure is an independent section, then you will need to consider the overall structure when counting the number of storeys in the independent section. When counting storeys for an independent section, any storey directly beneath the independent section, which is not below ground level, is to be counted in determining the number of storeys that comprise the building. This is demonstrated in Diagram 10.

If you have assessed that your structure is an independent section, when measuring height, you should measure your building from the lowest surface of the ground which touches the independent section (the ‘building’). For example, this may be the bottom of a staircase which is part of the independent section. You should measure to the point which is a horizontal projection from the top of the floor surface of the top storey of the independent section (the ‘building’).

Diagram 10 shows one 7-storey tower. Most of the structure is residential (tower A). There is a gym on the ground floor of the tower with its own access outside (section B).

In this example, using the method for counting storeys in the Regulations, tower A has 7 storeys and would be considered a higher-risk building.

Roof-tops

When counting storeys, any storeys which contain exclusively rooftop machinery or rooftop plant rooms should not be counted. Rooftop machinery is machinery which provides services to the building (for example, an air-conditioning system). Plant rooms are areas which contain machinery or equipment that provides services to the building. Only rooftop plant rooms and areas made up exclusively of rooftop machinery are excluded – for example, if floor three of a 7-storey building contained exclusively plant rooms and machinery, it should still be counted as a storey.

A storey must be fully enclosed to be considered a storey. The roof of a building should not be counted as a storey. Open rooftops such as rooftop gardens are not considered storeys and should not be counted as such when determining the number of storeys or measuring the height.

When measuring the height of a building, the building should be measured up to the top of the floor surface of the top storey, that is not exclusively rooftop machinery or plant rooms. This is demonstrated in diagram 11.

Diagram 11 shows a 6-storey residential tower with a rooftop garden.

In this example, height should be measured to the proposed floor surface of the top storey, as indicated by the arrow. The rooftop garden is not considered a storey, so the floor level of the roof should not be measured. Storeys should be counted from the first storey above ground. The proposed building in Diagram 12 has 6 storeys.

If the top storey is exclusively rooftop machinery or plant rooms, then the height of the building should be measured to the top floor surface of the storey below. This is demonstrated in Diagram 12.

Diagram 12 shows a 7-storey residential tower on sloped ground with a rooftop plant room.

In this example, height should be measured from ground level to the floor surface of the top storey, which is not a plant room, as indicated by the arrow. Storeys should be counted from the first storey above ground. The first storey in this building would not be considered below ground level as no part of its finished ceiling is below ground level for the overall building.

Based on the method for counting storeys in the Regulations, this building is considered 7 storeys and is a higher-risk building as it contains two or more residential units.

Gallery floors

Some buildings may have gallery floors. Gallery floors may also be known as mezzanines. A mezzanine is an internal area within a building. Mezzanines are intermediate areas that do not cover the whole length of the building between two main storeys.

Gallery floors should only be counted as a storey if the internal floor area of the gallery floor is at least 50% of the internal floor area of the largest above-ground storey above or below the gallery floor. Once a gallery floor meets the 50% threshold, it will become a storey and should be counted as such. For example, if a gallery floor, forming the third storey of a building, has an internal floor area half the area or more of the largest other storey, then this gallery floor should be counted as a separate storey. If the gallery floor is smaller than half the area of the largest storey, then it should not be counted as a separate storey. An example of how gallery floors should be counted is given in Diagram 13.

Diagram 13 shows one 7-storey residential tower with a gallery floor that has a floor area over 50% of the storey above it.

In this example, the gallery floor’s internal floor area is greater than 50% of the internal floor area of the storeys above it. Based on the method for counting storeys in the Regulations, the gallery floor in this structure would be considered a storey and the building would have 7 storeys.

Glossary of key terms used in this guidance

Access is defined in Regulation 4(7) of the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023. It means a doorway, archway or similar opening. Access which is only used in an emergency or for maintenance is not included. For example, a doorway between two buildings used regularly by residents counts as access, while an emergency exit between two buildings does not. If an exit is used both as an emergency exit and for regular access (for example, a front entrance used for both purposes), it counts as access. Under the Regulations the definition of access is limited to the doorway or opening, it does not include corridors, walkways or atriums.

An accountable person is the dutyholder during a higher-risk building’s occupation and must meet the statutory duties as set out in Part 4 of the Act. If an occupied higher-risk building has just one accountable person, they will automatically become the principal accountable person for that building. Where there are two or more accountable persons, the one responsible for the repair of the structure and exterior of the building will be the principal accountable person in line with the statutory definition.

The Building Safety Act 2022 (the Act) was granted Royal Assent on 28 April 2022. It implements the recommendations made in Dame Judith Hackitt’s report Building a Safer Future to create a new robust regulatory system for higher-risk buildings. Her recommendations set out clear duties and responsibilities for those who commission, design, construct and refurbish higher-risk buildings, and those who are responsible for making sure that buildings are safely managed when occupied. The Act is available at – Building Safety Act 2022 (https://www.legislation.gov.uk/ukpga/2022/30/contents/enacted).

The Building Safety Regulator (the Regulator) is charged with improving the safety and standard of buildings through three critical functions:
- leading the delivery of the new regulatory regime for higher-risk buildings;
- overseeing the safety and standards of all buildings; and
- facilitating improvement in the competence of industry and building inspectors
**Common parts88 are defined by section 72(6) of the Building Safety Act 2022. They include the structure and exterior of the building, except so far as included in a demise of a single dwelling or of premises to be occupied for the purposes of a business, or any part of the building provided for the use, benefit and enjoyment of the residents of more than one residential unit.

The core is the interior elements of a building which provide access to different parts of the building, such as a stair core or lift shaft.

Dutyholders (whether individuals or organisations) fulfil the key roles that are assigned specific responsibilities at particular phases of the building life cycle.

Higher-risk building is the technical term for buildings within the scope of the higher-risk regime. This guidance is designed to help users understand whether a building meets the criteria to be considered a higher-risk building.

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 Regulations) are Regulations which build on the provisions in the Act to complete the legal definition of higher-risk building. These are available in The Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 (https://www.legislation.gov.uk/uksi/2023/275/contents/made).

Overall structure is referred to as wider building in the Regulations. If two or more structures are attached, the overall structure refers to all the attached structures. When a structure is not attached to any other structure, the overall structure means that single structure.

A plant room is an area which contains machinery or equipment that provides services to the building.

A resident is a person who resides in a residential unit, regardless of tenure.

A residential unit is a dwelling or any other unit of living accommodation. Examples are a flat, studio flat, shared accommodation within university halls or a unit within a supported accommodation building.

A section: there are certain things to consider when deciding whether part of a building can be considered its own section. For part of a building to be a separate ‘section’, it should have its own egress out of the building. For example, commercial areas such as cafes and bars on the roof of or within towers should not be considered a separate section for the purpose of regulation 4(6)(b) if they share an exit with the residential floors below (despite having a different use). When assessing whether part of a building can be considered a separate section, it may also be relevant to consider what that part is used for. If an area of the building is used for a different purpose to another area, it is more likely to be considered its own section.

Structure is defined in Regulation 1(3) of the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023 as a roofed construction with walls.