UK mezzanine compliance
Check your mezzanine against UK building regulations
Free tools for fire rating, stairs, guarding and planning permission — every answer cites the Approved Document it comes from. No sign-up, no sales call to get a result.
- Cites Approved Documents B & K and the TCPA 1990
- Free to use
- No sign-up
- Part of the Autaimate family
Quick answer: when does a mezzanine need sign-off?
A mezzanine can clear one rule and still fail another. These are the four thresholds that decide it — verified against the source documents, not rules of thumb.
Fire · Part B
60 min
Fire protection once the floor is occupied
Stairs · Part K
170 mm
Maximum rise on a general-access stair
Planning · TCPA
200 m²
Retail floorspace that triggers permission
Building Regs
Always
Approval needed even when planning is not
Free compliance tools
Each tool encodes the actual Approved Document logic and shows the clause behind every result — so you can take the answer to Building Control with confidence.
Fire rating checker
Find out whether your mezzanine needs fire protection, based on use, size, and the 50% building-area rule under Approved Document B.
Open the toolStaircase & guarding checker
Check stair rise, going, width, handrail and guarding heights, the 100mm sphere test, risers per flight, and headroom against Approved Document K.
Open the toolPlanning permission checker
Check whether your mezzanine needs planning permission — the 200m² retail rule, change of use, and listed-building or conservation-area flags.
Open the toolCost calculator
Estimate the cost of a mezzanine floor by area, use, and finish — for warehouse, office, industrial, and retail projects.
Open the toolGuidance by sector
What a mezzanine needs depends heavily on how the floor is used. Each guide covers the cost, regulations and planning position for that sector, with the same cited figures behind the tools.
Warehouse mezzanine floors
The most common use. Storage-floor fire exemptions by size, loading for racking and forklifts, and why planning usually stays out of it.
Read the guide OfficeOffice mezzanine floors
An occupied floor: fire protection applies whatever the size, plus Part M access and the fit-out that is usually the bulk of the cost.
Read the guide RetailRetail mezzanine floors
The one sector where the 200m² planning rule bites — plus public-floor fire protection and step-free access.
Read the guide IndustrialIndustrial mezzanine floors
Plant and point loads drive the design, with three-phase power, extraction and compressed air routed to suit the machinery.
Read the guideHow it works
From question to cited answer in under a minute.
Pick a checker
Fire rating, staircase and guarding, or planning permission.
Enter your floor
Use, size and dimensions — plain questions, no jargon.
Get the verdict
An instant result with the Approved Document clause behind it.
When does a mezzanine need checking?
Three separate sets of rules decide whether a UK mezzanine floor is compliant, and they apply independently — a floor can clear one and still fail another. It is worth checking all three before the design is fixed, because changes are far cheaper on paper than in steel.
Fire protection is governed by Approved Document B. The first question is whether the floor is permanently occupied: an office or assembly area needs protection regardless of size, while a storage floor can be exempt depending on its dimensions, whether it covers more than half the building, and whether fire detection is fitted. The fire rating checker walks through that decision.
Stairs and guarding come under Approved Document K — rise, going, width, handrail and guarding heights, the 100mm sphere test, risers per flight and headroom all have set limits. The staircase & guarding checker tests a stair against each one.
Planning permission is usually not needed, because inserting a mezzanine is internal work. The main exception is retail: adding more than 200m² of floorspace to a shop counts as development. A change of use, a listed building, or a conservation area can also bring a project into planning control. Either way, a mezzanine almost always still needs Building Regulations approval.
Common questions
Does my mezzanine need fire protection?
It depends first on whether the floor is permanently occupied. Any mezzanine used as office, assembly, manufacturing, packing, canteen, or retail with public access needs fire protection regardless of its size. For infrequently accessed storage floors the rules are tiered by size and whether a fire detection and alarm system is fitted, and by whether the floor covers more than 50% of the building. Approved Document B sets the standard.
Does a storage mezzanine need a fire rating?
Not always. A storage mezzanine up to 10m by 10m that covers less than half the building is generally exempt. Up to 20m by 20m it can be exempt if a fire detection and alarm system is fitted. Anything larger than 20m by 20m, or covering more than 50% of the building, needs fire protection. These tiers come from Approved Document B.
What are the staircase rules for a mezzanine?
For a general-access commercial stair, Approved Document K sets a maximum rise of 170mm, a minimum going of 250mm, a minimum width of 1200mm, handrails 900–1000mm above the pitch line, and guarding of 900mm alongside the flight and 1100mm at floor edges and landings. No 100mm sphere should pass through any guarding gap, and headroom must be at least 2000mm. Utility stairs are allowed a slightly steeper rise.
Do I need planning permission for a mezzanine?
Usually not. Inserting a mezzanine is normally internal work, which is not development. The main exception is retail: adding more than 200m² of floorspace to a shop counts as development and needs planning permission. A change of use, a listed building, or a conservation area can also trigger the need for permission, so those are worth checking separately.
Is inserting a mezzanine classed as development?
Section 55 of the Town and Country Planning Act 1990 treats works that only affect the interior of a building as not development, so most mezzanines fall outside planning control. The exception, set by development order, is a mezzanine that increases retail floorspace by more than 200m² — that is treated as development and needs permission.
Are these tools a substitute for Building Control?
No. They give informational guidance to help you understand the rules before you commit to a design. Final compliance determination requires a qualified structural engineer and Building Control approval. Treat the results as a starting point, not a sign-off.
Do the rules differ in Scotland and Wales?
Yes. These tools reflect the Approved Documents and planning rules that apply in England. Scotland has its own building standards and planning system, and Wales has its own building regulations and planning order, so figures and thresholds can differ. Check the relevant national guidance for projects outside England.
Planning a mezzanine project?
Tell us about your floor and we will come back with a tailored quote. No obligation, and the checkers stay free either way.