Building Safety Act 2022: How to accurately measure your building height

Last updated: 18th March 2026

To ensure compliance with the Building Safety Act 2022 (BSA 2022) and relevant fire safety regulations, having accurate building measurements is crucial for determining which guidelines to follow. Firstly, you must identify whether your building is a ‘higher-risk building’, 'relevant building', or neither, as well as its height category, to understand its risk rating, implement appropriate safety measures, and protect tenants. 

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Building Safety Act 2022  

The Building Safety Act (section 117 for relevant buildings and section 31 and 65 for higher-risk buildings) outlines the requirements for buildings based on their height in metres or the number of storeys. The height of a building determines its category and the regulations that apply to it. The BSA 2022 and PAS 9980 provide detailed instructions on measuring building height for both single structures and multiple structures that are connected. For more information, you can access the government guidance here.

What is a ‘relevant building’? 

The leaseholder protections in the Building Safety Act only apply to relevant buildings. A building is defined as a relevant building under the BSA 2022 if it meets the following criteria: 

• it is at least 11 metres tall or has at least five storeys 
• it contains at least two dwellings 
• it is not leaseholder-owned 

To accurately determine whether you have a relevant building, access the government guidance here. 

What is a ‘higher-risk building’? 

A higher-risk building is any building in England that: 

• is at least 18 metres in height or has at least seven storeys  
• contains at least 2 residential units 
• meets a certain set of use criteria 

To discover more expert insights into accurately measuring your building height, the Building Safety Act Gateways, and maintaining a golden thread of information, catch up on our recent webinar, 'Building Safety: Gateways, Golden Thread, and Building Heights', available on demand now.

How to measure the height of a building  

It is important to remember every building is unique, so you must tailor your approach to account for individual factors. Consider what constitutes a floor and storey and be prepared for challenges based on the building's specific characteristics. Measurements must be done on a case-by-case basis, as different circumstances dictate where you measure from. We've broken down the key measurement guidelines below to simplify the process: 

• Measure from the surface level of the uppermost floor to the lowest point on the ground outside the building. 

• Determine the ground level carefully, considering any small spaces or variations in terrain.  
• Do not include any storeys that are below ground level (including underground car parks).  
• In situations where the ground is sloped, measure from the lowest level of the ground directly adjacent to the structure. 

Source: https://www.gov.uk/guidance/criteria-for-being-a-higher-risk-building-during-the-occupation-phase-of-the-new-higher-risk-regime

• Do not count any storeys that contain exclusively rooftop machinery or rooftop plant rooms. 
• Gallery floors (also known as mezzanines) 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 should be counted as a storey.  

If you have a unique building and are unsure where to measure from, undergoing a Measured Survey is the foolproof method to ensure accuracy. 

Building height categories  

A building falls into a category based on either its height or the number of storeys; it does not need to meet both criteria. Under the Fire Safety (England) Regulations 2022, you must adhere to the following requirements for each specific building type: 

All buildings with two or more sets of domestic premises  

• Provide fire safety instructions to residents 
• Provide fire door information to residents 

Residential buildings above 11 metres or five storeys  

• All of the above  
• Check communal fire doors at least every three months 
• Check flat entrance doors at least every 12 months 

Residential buildings above 18 metres or at least seven storeys  

• All of the above 
• Implement a secure information box  
• Assess the external wall system
• Create floor plans and building plans 
• Check lifts and fire-fighting equipment 
• Use wayfinding signage 
• Register the building with the Building Safety Regulator  
• Prepare safety cases and safety case reports 
• Implement a resident engagement strategy  
• Create a mandatory occurrence reporting system
• Have a complaints system  

Common higher-risk building misconceptions

There are several common misconceptions when it comes to height and what qualifies a building as higher-risk:

• It is not just about high-rise towers: mid-rise residential buildings can fall within scope

• Height alone is not enough: the building must also meet use criteria (e.g., residential units)

• Refurbishment projects can trigger HRB requirements if they affect a qualifying building

• Mixed-use buildings may fall into scope depending on their residential composition

Understanding these nuances early in a project can prevent costly redesigns and regulatory delays later.

Frequently Asked Questions (FAQs)

Q: How do we go about calculating the height of a building when a flat is a duplex? 

A: UK fire safety guidance is not affected by whether a flat is a duplex or a single level. The height is determined by the top story of the building, so even if that duplex is two or three levels up, the entrance to the duplex is the top level of the building. The height is to the finished floor level of the top of the occupied story, not the roof, parapet, ceiling, or anything else. 

Q: Where on the ground do you measure a building from?

A: You measure the height from the lowest point where ground exists adjacent to the building. 

Q: When is a storey classed as a storey? 

A: If there is a storey that is both above and below the ground with the ceiling above ground level (even by an inch), this counts towards the number of storeys in the property. However, if the ceiling level and the ground level were the same, that storey would not count. 

Q: Would a rooftop garden be classed as a floor? 

A: No because it is not a place where people live, and therefore it is not counted as a storey within the building. This is in the same way that a plant room would not be counted as storey. 

Still unsure about measuring your building or need assurance that you have measured it correctly? Accurate measurements are essential for compliance and safety; don’t leave it to guesswork. Speak to one of our experts who are on hand to provide you with a Measured Survey to ensure your building is measured correctly and meets all relevant regulations.