Relevant buildings: the 18 metre and seven storey test
A fire statement is required for relevant buildings at 18 metres or seven storeys. Here is where the datum sits, which storeys are excluded, and how podium schemes are treated.
A relevant building for Planning Gateway One is one that contains two or more dwellings, or educational accommodation, and is 18 metres or more in height or has seven or more storeys. Meet either limb of the height test and the application needs a fire statement, with the Health and Safety Executive consulted as the Building Safety Regulator. Miss the measurement by 200 millimetres and you have an invalid application, a delayed determination and an awkward conversation with a client. The 18 metre and seven storey test rewards precision at the section drawing stage.
Where the threshold comes from
Article 9A of the Town and Country Planning (Development Management Procedure) (England) Order 2015 introduced the fire statement requirement for applications for relevant buildings. It sits alongside the Building Safety Act 2022 framework, which uses the same headline numbers to define higher-risk buildings for the gateways that follow at design and construction stage.
The point of the planning stage requirement is narrow. It asks the applicant to show that fire safety has shaped the design before the layout is fixed, because access, water supply, escape routes and the position of cores are all extremely difficult to change once permission has been granted on a settled plan.
Two limbs, either of which catches the building. Height, or storey count. Not both.
The fire statement itself is submitted on the published form, and the Health and Safety Executive responds as a statutory consultee. A response that asks for more information will extend the determination period, so the quality of the submission has a direct effect on the programme.
How height is measured for this purpose
Height is measured from ground level to the floor surface of the top storey. Not to the parapet, not to the ridge, and not to the top of the lift overrun.
Ground level is taken at the lowest part of the ground surface adjacent to the building, which matters on sloping sites where the difference between the high and low sides can be a full storey. A storey consisting exclusively of plant or machinery is left out of the measurement.
| Element | In or out |
|---|---|
| Finished floor level of the top occupied storey | The measurement point |
| Parapet, roof structure, lift overrun | Out |
| Roof-top plant storey | Out |
| Storeys below ground level | Out of the storey count |
| Lowest adjacent ground level | The datum |
Record the calculation on the section drawing, with levels expressed above ordnance datum and the datum point identified. A Fire Statement that states the height without showing how it was derived gives the validation officer nothing to check.
Counting storeys, including the awkward ones
The storey count runs separately from the height calculation and catches buildings with generous floor to ceiling heights that never reach 18 metres.
Storeys below ground level are excluded from the count. A roof-top storey used only for plant is excluded. A mezzanine counts where its floor area is large enough relative to the largest storey in the building, which is where design teams disagree with each other most often.
The practical trap is the double height entrance or the commercial ground floor. A scheme with a 5 metre retail podium, seven residential floors above and a plant enclosure at roof level can sit below 18 metres and still reach seven storeys, or reach 18 metres with six. Count and measure both, every time.
Buildings containing two or more dwellings
The building use test is as important as the height. The requirement applies to buildings containing two or more dwellings and to buildings containing educational accommodation. A single large house, an office block or a hotel of the same height is not caught by this particular requirement, though other fire duties apply to all of them.
Student accommodation, supported housing and care settings need care, since whether the units are dwellings for this purpose depends on their configuration. Where the classification is arguable, set out the reasoning in the submission rather than leaving the officer to infer it.
Mixed use blocks, podiums and separate buildings
Podium schemes produce the hardest questions. Where several residential blocks sit on a shared podium, the answer to whether each block is a separate building depends on structural independence above the podium level and on how the parts are connected.
This is not a drafting preference. It changes whether each block is measured on its own or whether the structure is treated as one building, and therefore whether the threshold is met. Get a view from the fire engineer and the building control approver early, record it, and be consistent across the planning application, the gateway submissions and the design stage reports. A Fire Safety Strategy is where that reasoning normally lives, and it is a fire engineering document requiring the relevant competence.
Where the regimes differ, they differ in scope rather than in the numbers. The planning requirement uses relevant buildings, the Building Safety Act uses higher-risk buildings, and the Building Regulations use other thresholds again for matters such as sprinklers and staircase provision. Check the current Approved Document B position separately, because those thresholds have moved in recent years and transitional arrangements apply.
Recording the measurement in the submission
- Show the datum point on the site section, with existing and proposed levels.
- Annotate the finished floor level of the top occupied storey.
- State the resulting height in metres to two decimal places.
- Schedule the storeys, marking those excluded and the reason.
- State whether the building contains two or more dwellings.
- Confirm the conclusion on the application form and in the fire statement.
Where the building sits close to the threshold, say so explicitly and explain the treatment. An officer who can see the reasoning will accept it. An officer who suspects a building has been designed to 17.9 metres to avoid a requirement will look harder at everything else in the application.
Design consequences follow either way, and they run past the fire statement into the foundations and the structure. Basement levels change the datum, and a Basement Impact Assessment may be needed for reasons that have nothing to do with fire. Roof level plant affects the measured height only if it forms a storey, and roof level plant and photovoltaics on a flat roof covers how that is treated.
An illustrative example: a block on a site falling 1.2 metres across its footprint, measured from the low side, can be a relevant building while the same block measured from the high side would not be. The datum is not a matter of choice.
Where a scheme is refused or amended after a Gateway One consultation response, keep the measurement note with the revised drawings. Section 73 applications and later amendments are assessed against the same tests, and a change in ground levels during detailed design can bring a building into the regime that was outside it at outline.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
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Frequently asked questions
Where is the 18 metres measured from and to?
From ground level to the floor surface of the top storey. Ground level is taken at the lowest part of the ground adjacent to the building, which matters on sloping sites. The measurement excludes parapets, roof structures, lift overruns and any storey used exclusively for plant or machinery.
Which storeys count towards seven?
Storeys above ground level, excluding any roof-top storey used only for plant. Storeys below ground level are excluded from the count. Mezzanines count where their floor area is large enough relative to the largest storey, which is the point design teams most often disagree on, so record the reasoning.
Does the requirement apply to offices and hotels?
Not this one. The planning stage fire statement requirement applies to buildings containing two or more dwellings and to buildings containing educational accommodation. Other fire safety duties apply to all building types under the Building Regulations and the fire safety legislation, so the absence of a fire statement does not mean an absence of obligations.
How are podium schemes treated?
Whether each block above a shared podium is a separate building depends on structural independence and how the parts are connected. That answer changes whether the threshold is met for each block. Take a view from the fire engineer and the building control approver early, and keep it consistent across the planning and gateway submissions.
What if the building is just below the threshold?
Say so explicitly in the submission and show the calculation with the datum identified and the storey schedule set out. Officers accept reasoning they can check. A building that appears to have been designed to sit fractionally below a threshold, without explanation, attracts scrutiny across the rest of the application.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.