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Our guide on how to measure and check if your building is classed as “relevant” and / or “high risk”.
Article By: Tom Ayre
Last Update: March 2024
The Building Safety Act 2022 was implemented on June 28, 2022, with the aim of promoting the protection of individuals in and around structures while enhancing their quality.
Under this legislation, proprietors of structures that exceed certain heights or numbers of stories are now subject to a higher degree of accountability when it comes to financing necessary renovations. Furthermore, the Secretary of State has been granted the authority to limit the capacity of negligent builders to construct new dwellings and empower owners to take legal action against them.
It is crucial to know the height classification of your building to determine if it falls under the “relevant” and/or “high-risk” categories. In the following guide, we will demonstrate how you can determine this classification.
A building is classed as relevant if it confirms to the following parameters:
– Building height is 11 metres
– Or has at least 5 storeys.
– It contains at least two dwellings
– It is not a leaseholder-owned building
If a building is classified as “relevant,” it implies that the leaseholder protections will be applicable.
Please read more about the definition of a relevant building here.
A building is classed as high risk if it confirms to the following parameters:
– Building height is 18 metres
– Or has at least 7 storeys.
– It contains at least two dwellings.
If a building is classified as high risk, the owners and managers of high-rise residential buildings will be subject to new legal duties. The initiative will urge those responsible for the safety management of higher-risk buildings to proactively prepare for an upcoming wave of regulatory changes, ensuring they are prepared to step up and comply with the new requirements.
The height of a building is defined in the Building Safety Act 2022 as follows.
“(2)The height of a building is to be measured from ground level to the finished surface of the floor of the top storey of the building (ignoring any storey which is a roof-top machinery or plant area or consists exclusively of machinery or plant rooms).
(3)When determining the number of storeys in a building—
(a)any storey below ground level is to be disregarded;
(b)any mezzanine floor is to be regarded as a storey if its internal floor area is at least half of the internal floor area of the largest storey in the building, which is not below ground level.
(4)In subsection (2) “ground level”, in relation to a building, means—
(a)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 immediately adjacent to it.
(5)For the purposes of subsection (3) a storey is “below ground level” if any part of the finished surface of the ceiling of the storey is below the level of the surface of the ground immediately adjacent to that part of the building.”
Building Safety Act 2022 – Section 118
The ground height around a building can change fairly drastically, even on particularly flat sites. The act states that.
“the level of the lowest part of the surface of the ground immediately adjacent to it.”
At THS Concepts, we have understood this to be the lowest level of ground, butting up to the building. We think that on in some blocks of flats that are split with a party wall / fire wall, then each block needs to be considered on its own. This is because each block may have differing ground and top floor heights. We have explained this in the diagram below.
The top floor in a building is defined as:
” the finished surface of the floor of the top storey of the building (ignoring any storey which is a roof-top machinery or plant area or consists exclusively of machinery or plant rooms).”
This is fairly simple in that, if the floor has someone living there, this will be considered an occupied floor. Conservatively, we think that measurements should be taken to the top part of the top most floor. It is unusual, but sometimes the levels change within a floor, so this must be considered.
The number of storeys in a building is defined as:
“(3)When determining the number of storeys in a building—
(a)any storey below ground level is to be disregarded;
(b)any mezzanine floor is to be regarded as a storey if its internal floor area is at least half of the internal floor area of the largest storey in the building, which is not below ground level.”
So simply, basements and below ground floors can be ignored. This is because the height is considered above the ground. For mezzanines / half floors, then these are ignored unless they are unusually large (at least half the internal floor area).
Measuring the height of a building first starts with establishing the lowest point on the building / sub block you are measuring. To do this, we would recommend walking around the building and inspecting the height difference from the DPC (damp proof course) level to the ground. Where this height is at its greatest is the point at which the ground is at its lowest. It obviously worth checking that the DPC doesn’t step up or down around the building.
Once you have found the lowest point then, using a tape or laser, measure up from the ground to the DPC level (that we assume runs the same height around the building). Write this measurement down and take a photo of the area you are considering to be the lowest level.
Next, we are going to have a look around on the top floor of the building and find the highest point. Usually in a purpose built block, the top floor is all one level and at the same height as the top of the communal stairs.
Once established, we now need to measure all the way down to the ground floor. Hopefully this can be done easily by going down a communal stairway. If not, you may have to manoeuvre out of a window (carefully) or take a few measurements down the stairs. When you reach the ground floor, you need to measure the height of that down the DPC level.
You now have all the heights you need. You just need to gather your ground to top floor height, and add this on to your DPC to ground floor and DPC to ground level. For instance:
Top Floor > Ground Floor = 9.25 m
Ground Floor > DPC = 0.12 m
DPC > Ground Level = 0.17 m
Total = 9.25 + 0.12 + 0.17
This equates to: 9.54 metres.
Please find below a calculator designed to determine the classification of your building as “relevant” and/or “high risk”.
For this calculator, you will need to know:
Kindly note that while using this tool, you are responsible for any outcomes or decisions made.
When measuring the height of a building, it is critical that you take your time and work methodically to ensure you are correct. Access in and around the buildings may be the biggest issue when it comes to the on-site work. Ensure you have full access to the building, so you can establish the top most height and lowest ground level easily.
If in doubt, consider using a company like THS Concepts, who can quote and issue a report on the exact height of a building.
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76 Quill Street, Finsbury Park, London, N4 2AD
THS Concepts has a passionate team of surveyors and CAD draughtsman delivering detailed, thorough and accurate surveys and CAD drawings. We are far more than just a land and building surveying company.
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