Building Height Assessments: A Guide to the Building Safety Act 2022
Building height determines your BSA 2022 obligations. Learn how height is measured, when assessments are needed, and what the thresholds mean.
The Building Safety Act 2022 made building height one of the most important factors in property management and transactions. Get the measurement wrong, and you could face blocked sales, unexpected remediation costs, or even criminal penalties.
Whether you’re a building owner, leaseholder, or managing agent, understanding how height is measured and what the thresholds mean is now essential. Here’s what you need to know.
Why Does Building Height Matter Under the Building Safety Act 2022?
Building height determines whether your property is classified as a “relevant building” or a “higher-risk building” – each triggering different legal obligations, from leaseholder cost protections to mandatory registration with the Building Safety Regulator.
There are two critical thresholds to understand:
11 metres or 5 storeys – Buildings meeting either criterion (with at least two dwellings) become “relevant buildings.” This activates leaseholder protections under the Act, including caps on remediation costs and protection from cladding charges.
18 metres or 7 storeys – These are classified as “higher-risk buildings.” They must be registered with the Building Safety Regulator, have a Principal Accountable Person appointed, and maintain ongoing safety documentation. Failure to register is a criminal offence.
If your building sits close to either threshold, accurate measurement isn’t just helpful – it’s legally necessary.
How Is Building Height Measured Under the BSA 2022?
Height is measured from the lowest point of ground adjacent to the building to the top of the floor surface of the top storey – not the roof.
This methodology catches many building owners off guard. A building that appears to have six storeys from its main entrance might qualify as higher-risk when measured from the lowest adjacent ground level.
Several elements are excluded from the count:
- Basements – Any storey with its ceiling below the adjacent ground level is ignored
- Rooftop plant rooms – Storeys containing only machinery or plant are excluded
- Mezzanines – Only count as a storey if their floor area is at least 50% of the largest above-ground storey
For buildings on sloping sites, the measurement starts from the lowest point where the ground meets the building. This can push classifications higher than expected.
The treatment of roof gardens remains under review following a 2024 tribunal decision, though current government guidance maintains that open roof terraces should not count as storeys.
When Do You Need a Professional Building Height Assessment?
Professional assessment is essential when your building sits close to either threshold, has a sloping site, complex interconnected sections, or when you need defensible documentation for property transactions.
Conveyancers cannot verify building height themselves – this is explicitly outside their role. Instead, they rely on certificates provided by landlords and leaseholders. If those certificates contain inaccurate height information, transactions can stall or fall through entirely.
A professional height survey provides:
- Precise measurements using laser scanning technology
- Clear documentation of methodology
- Professional indemnity coverage
- A defensible record if classifications are later disputed
For buildings near the 11-metre or 18-metre thresholds, the cost of a professional survey is minimal compared to the consequences of getting it wrong.
Getting Your Building’s Height Right
Understanding your building’s height classification under the Building Safety Act 2022 is no longer optional. Whether you’re preparing for a sale, responding to leaseholder enquiries, or ensuring regulatory compliance, accurate measurement is the foundation.
At Blackacre, our Chartered Surveyors provide Building Height Measurements using precision laser scanning equipment. Our surveys deliver accurate, documented assessments that satisfy BSA 2022 requirements and provide certainty for property transactions.
If you need a Building Height Assessment, please get in touch.
e: info@blackacresurveyors.com
t: 0203 476 9561