What Is a Higher-Risk Building? UK HRB Guide
Understanding Higher-Risk Buildings Under the Building Safety Act
A Higher-Risk Building, commonly referred to as an HRB, is a building that falls within the more stringent regulatory regime introduced by the Building Safety Act 2022. In simple terms, many residential buildings in England that are at least 18 metres high or have at least seven storeys, and contain at least two residential units, are HRBs. However, the legal test is more detailed than this headline definition, particularly where buildings contain mixed uses, basements, rooftop areas, connected structures or unusual changes in ground level.
Correctly identifying whether a building is an HRB matters before design work, procurement or construction begins. The answer can determine who regulates the work, what information must be prepared and whether formal approval is required before construction starts. Our High Risk Building Hub brings together our wider guidance on the Building Safety Act, while our Higher-Risk Building consultancy service supports owners, developers and project teams through these requirements.
One of the first services we provide is HRB diagnosis: establishing whether a particular building actually falls within the statutory definition and, if it does, what that means for the proposed works. This can be especially important when purchasing a property, planning an apartment refurbishment or considering work in a complex mixed-use building. Our article on assessing HRB risk before commitment explains why resolving this question early can prevent major programme, cost and regulatory problems later.
The Government Criteria for a Higher-Risk Building
For building work carried out under the design and construction regime, government guidance defines Higher-Risk Buildings as buildings in England that are at least 18 metres in height or have at least seven storeys and contain at least two residential units, or are a hospital or care home meeting the same height or storey threshold. Certain buildings are specifically excluded, including buildings used entirely as hotels, secure residential institutions or military barracks, together with specified military accommodation.
The occupation regime is slightly different. Broadly, an occupied building is an HRB where it meets the 18 metre or seven-storey threshold and contains at least two residential units, subject to the statutory exclusions. This distinction matters because the Building Safety Act uses related but not identical definitions for building work and for the ongoing management of occupied higher-risk residential buildings.
The height and storey tests are alternatives. A building does not need to satisfy both. A six-storey building may still be an HRB if the relevant measured height reaches 18 metres, while a seven-storey building may qualify even if the measured height is below 18 metres.
How Are Height and Storeys Measured?
This is where apparently simple HRB assessments often become more complicated. Height is not measured casually to the roofline. Under the relevant rules, it is generally measured from the appropriate ground level to the top floor surface of the top storey, excluding a top storey used exclusively for rooftop machinery or plant. On sloping sites, the applicable ground level can be the lowest part of the ground adjoining the building.
Storeys below ground level are generally disregarded where they meet the statutory test for being below ground. Rooftop plant areas used exclusively for machinery or plant are also excluded from the storey count, and current government guidance states that open rooftop gardens are not counted as storeys. Connected buildings and independent sections create another layer of analysis because the legislation contains specific rules for deciding what constitutes the relevant “building”.
This is why we do not recommend relying solely on estate agent particulars, planning drawings or a building’s marketing description. A proper HRB determination should consider the building’s use, legal configuration, height, storey count and physical relationship between connected structures.
Why HRB Status Changes a Refurbishment Project
For clients altering a flat within an HRB, the regulatory consequences can be substantial even where the apartment itself is small. Relevant building work may fall under the direct oversight of the Building Safety Regulator rather than the conventional building control route, and Gateway 2 approval may be required before controlled work can begin. The project team must therefore establish the regulatory route before construction is programmed.
Our completed Gateway 2 approval for a Higher-Risk Building demonstrates how architectural design, fire strategy, consultant information and Principal Designer duties need to work together. Our East Village HRB determination project also shows that the use of the particular space being altered does not necessarily remove the wider building from the HRB regime.
Starting first and resolving the position later can create serious difficulties. We are increasingly approached where work has already commenced before the correct regulatory route was understood. Our article on retrospective Higher-Risk Building permission explores the complexity that can follow when compliance is considered only after work has taken place.
Diagnosing Whether Your Building Is an HRB
Folly Architects provides specialist HRB diagnostic and advisory services for private clients, developers, building owners, managing agents and professional teams. Our approach is to establish the classification first, then identify the regulatory consequences for the proposed work. Depending on the building, this can involve review of measured surveys, historic drawings, Land Registry or building information, floor uses, levels, storey arrangements and the relationship between different parts of a wider structure.
Where the position is borderline or unusually complex, the assessment needs to be recorded carefully rather than reduced to a single height figure. This is particularly relevant to historic mansion blocks, mixed-use developments, buildings on sloping sites and buildings that have evolved through multiple phases of construction. Our work at Tea Trade Wharf illustrates how heritage and HRB considerations can overlap in an existing building.
These diagnostic services form part of our wider UK-leading Higher-Risk Building support, combining architectural design, Building Regulations knowledge, Principal Designer capability, regulatory strategy and practical delivery experience. Where an HRB project proceeds, our Principal Designer service can provide structured design compliance leadership through the regulated process.
Frequently asked questions
The following questions and answers summarise common queries relating to this topic.
For the design and construction regime in England, a building is generally a Higher-Risk Building if it is at least 18 metres high or has at least seven storeys and contains at least two residential units, or is a qualifying hospital or care home. The legislation also contains specific exclusions and detailed rules for defining, measuring and counting the building.
No. The tests are alternatives. A building may qualify because it is at least 18 metres high even if it has fewer than seven storeys, or because it has at least seven storeys even if its measured height is below 18 metres, provided the relevant use criteria are also satisfied.
Not necessarily. Storeys that meet the statutory definition of being below ground level are disregarded when counting storeys. Ground level and basement conditions therefore need to be assessed carefully, particularly where a building sits on sloping land or has partially exposed lower floors.
Yes. Folly Architects provides specialist HRB diagnostic services to review the building's height, storey count, use, configuration and available records. We can provide an early-stage assessment of whether the statutory HRB criteria are likely to apply and explain the regulatory implications for the proposed project.
If the building is an HRB and the proposed work requires Building Safety Regulator approval, starting work without following the correct process can create significant regulatory and programme problems. HRB status and the applicable approval route should therefore be established before controlled work begins.
What Should You Do If You Are Unsure?
If there is genuine doubt over whether a building is an HRB, the safest commercial approach is to resolve that question before committing to construction dates or assuming a conventional building control route. The consequences of getting the classification wrong can include redesign, abortive consultant work, programme delay, enforcement risk and work being unable to proceed as intended.
The starting point should be a structured review of the building against the current statutory criteria, followed by an assessment of the proposed works. Folly Architects can provide this review as a focused early-stage service or as the first stage of a wider HRB appointment. For more detailed guidance, visit our High Risk Building Hub or contact us to discuss a building where the HRB status is unclear.
Contact us
If you would like to discuss a project, clarify regulatory requirements, or understand how our experience may be relevant to your work, you are welcome to get in touch.
