Mezzanine floor building regulations: key facts
- In England and Wales, building work in premises covered by the Fire Safety Order 2005 needs a full plans application. A building notice isn't an option for a warehouse.
- Approved Document B treats a mezzanine as a gallery: a floor that doesn't cover the whole footprint and is open to the floor below.
- A gallery larger than half the area of the space it projects into counts as a storey.
- A storage-only raised floor can skip the normal fire resistance if it meets every condition in Approved Document B paragraph 7.7, including size limits.
- Industrial stairs: Approved Document K points to BS 5395-3 or BS 4211. Floor edges in warehouses need guarding at least 1100 mm high.
- You can use local authority building control or a registered building control approver. Planning permission is a separate question.
Does a mezzanine floor need building regulations approval?
In practice, yes. The regulations don't use the word mezzanine, but a new floor inside a building is building work because it affects structure, fire safety and escape. Approved Document B has specific guidance for galleries and raised storage floors.
It's easy to think of a mezzanine as equipment, like racking. That's the wrong starting point. It's a structural floor that people walk on, it puts new loads on your slab, and it changes how people get out in a fire. Those are exactly what the Building Regulations 2010 control.
The regulations don't mention mezzanines by name. Approved Document B (fire safety) deals with them under two names:
- Gallery: "a floor or balcony that does not extend across the full extent of a building's footprint and is open to the floor below".
- Raised storage area: raised, free-standing floors, "sometimes supported by racking", in single storey industrial and storage buildings.
GOV.UK's advice is to check with a building control body if you can't decide. For a warehouse mezzanine, assume you need approval and plan the time from the start.
Still deciding whether a mezzanine suits your building? Start with our guide to mezzanine floors.
Why is a mezzanine "building work" under the regulations?
Regulation 3 of the Building Regulations 2010 covers erecting or extending a building and any material alteration. An alteration is material if it could leave the building failing a key requirement, such as structure, fire safety, escape or access, at any stage.
Regulation 3 defines building work. It includes the erection or extension of a building, and the regulations say a building includes part of a building. It also includes material alteration: work that would at any stage leave the building failing a "relevant requirement" it met before, or make an existing shortfall worse.
| Relevant requirement | How a mezzanine touches it |
|---|---|
| Part A: structure | New columns and beams, point loads on the slab |
| B1: warning and escape | People upstairs need alarms they'll hear and a safe way out |
| B3: internal fire spread (structure) | The structure may need fire resistance |
| B4 and B5: external fire spread, fire service access | Firefighters may have to work under or across the floor |
| Part M: access | Getting people from one level to another |
| Part T: toilets | If toilets are added or changed |
A mezzanine affects at least structure, escape and fire spread, so the design has to show how each is met.
What does Approved Document B say about mezzanine structure and fire resistance?
Gallery structures are elements of structure and normally need fire resistance. A storage-only raised floor can avoid that if it meets every condition in paragraph 7.7, including size limits that relax with fire detection or sprinklers.
This describes Approved Document B Volume 2 (buildings other than dwellings), the version on GOV.UK for use in England. It's guidance on meeting the regulations. Another approach is possible, but you'd have to show building control that it works.
Is your mezzanine a storey?
Approved Document B counts a gallery as a storey "if its area is more than half that of the space into which it projects" (any gallery counts in assembly buildings). Several galleries in one space covering more than half its floor area make the building multi-storey. Once that happens, more of the fire and escape guidance applies.
Does the structure need fire protection?
A gallery is an element of structure. Paragraph 7.1 says floor and gallery structures "should have, as a minimum, the fire resistance given in Appendix B". Appendix B adds that most elements of structure in a single storey building may not need fire resistance, but they do if they support a gallery. That's why many office and production mezzanines have fire-rated ceilings and column casings.
The raised storage area concession
Paragraph 7.6 accepts that normal fire resistance "may be too onerous" for raised storage floors in single storey industrial and storage buildings. Paragraph 7.7 allows a structure without it if all of these apply:
- One tier only, used for storage only.
- Few people on it at any one time, and none of them members of the public.
- Open above and below to the space it's in.
- Means of escape follows Sections 2 to 5 of Approved Document B.
- Not more than 10 m in width or length, and no more than half the floor area of the space.
The size limits relax in three cases:
- Fire detection and alarm to BS 5839-1 on the lower level: up to 20 m in either width or length.
- Agreement with the building control body and the fire and rescue service, considering firefighter safety and travel over or under the floor.
- Sprinklers throughout to Appendix E: no size limit.
How do people get off a mezzanine in a fire?
Requirement B1 needs early warning and a safe escape route to outside. Approved Document B limits travel distance by use: for normal hazard storage, 25 m where escape is in one direction only and 45 m where there's more than one.
Requirement B1 asks for "appropriate provisions for the early warning of fire, and appropriate means of escape". A mezzanine puts people at height, often in a far corner, so escape is usually the biggest design question.
| Use (Approved Document B, Table 2.1) | One direction only | More than one direction |
|---|---|---|
| Storage or industrial, normal hazard | 25 m | 45 m |
| Storage or industrial, higher hazard | 12 m | 25 m |
| Office | 18 m | 45 m |
Higher hazard includes significant amounts of hazardous goods, such as compressed gases, corrosives, and liquids with a flash point below 65°C (Approved Document B names whisky and other alcoholic liquor). If the layout isn't known, it says to assume the direct distance is two-thirds of the travel distance. Shelving on the deck lengthens the real route.
- The number of escape routes depends on people numbers and travel distances (paragraph 2.3). On a long deck, the one-direction limit often means a second stair.
- Escape stairs should normally be protected stairways. An unprotected stair is allowed where travel distance and people numbers are very limited, and raised storage areas are given as an example (paragraph 3.23).
- Smaller premises may follow the small premises guidance if no storey is over 280 m² and there are no more than two storeys plus a basement (paragraph 2.2).
Measure before you ask for quotes: the longest walk from any point on the deck to each stair; the walk from the foot of each stair to a final exit; how many people will be up there at the busiest time; and whether the fire alarm can be heard upstairs.
What do Approved Documents K and M ask for on stairs, edges and access?
Approved Document K says industrial stairs, ladders and walkways should follow BS 5395-3 or BS 4211, and floor edges in warehouses need guarding at least 1100 mm high. Approved Document M says altered ways of getting between levels must comply.
Stairs. Requirement K1 says stairs must be safe for people moving between levels. For industrial buildings, Approved Document K paragraph 1.33 points to BS 5395-3 (industrial type stairs, permanent ladders and walkways) or BS 4211. A lower standard may be acceptable where access is only for maintenance. A stair used every shift isn't that.
Edges. Requirement K2 needs barriers where necessary to stop people falling, including at the edges of floors and galleries. Diagram 3.1 sets minimum heights:
| Factories and warehouses (light traffic) | Minimum height |
|---|---|
| Stairs, ramps | 900 mm |
| Landings and edges of floors | 1100 mm |
Guarding must resist the loads in BS EN 1991-1-1 with its UK National Annex. It isn't needed where it would obstruct normal use, such as loading bays, so a mezzanine loading point usually has a pallet gate instead of an open edge. Approved Document K also cross-refers to the Workplace (Health, Safety and Welfare) Regulations 1992 and the Work at Height Regulations 2005, which govern how you use the floor every day.
Access. Approved Document M Volume 2 says alterations to "arrangements for people to get from one level to another" must comply, and the building must be no less compliant afterwards. It calls a passenger lift the most suitable way between storeys, with a lifting platform as an alternative in existing buildings. How this applies to a storage-only deck is one to settle early with building control, especially if offices or staff facilities go upstairs. The Equality Act 2010 applies regardless.
Full plans or building notice, and who checks the work?
For a warehouse in England or Wales it's full plans, because regulation 12(3) requires them for building work in premises covered by the Fire Safety Order. You can use the local authority or a registered building control approver, and you should get a completion certificate at the end.
A building notice lets you start two days after submitting, without formal approval. But regulation 12(3) requires a full plans application for building work in a building the Regulatory Reform (Fire Safety) Order 2005 applies to. That Order covers all premises except domestic ones and a short list of exceptions, so a warehouse mezzanine needs full plans.
Who checks it. For anything that isn't a higher-risk building, GOV.UK says you can choose your local authority or a registered building control approver. An approver tells the council about your work by giving an "initial notice". Your supplier may handle the application, but ask to see what's submitted.
Time and fees. GOV.UK says to expect a full plans decision within 5 weeks, or 2 months with your consent. Councils base fees on their costs; approvers negotiate them. Get the fee in writing.
- General arrangement drawings: deck size, column grid, stairs and gates.
- Structural calculations and the design floor loading.
- Base plate loads and evidence the slab can take them.
- Fire strategy: the 7.7 concession, or the fire protection proposed.
- Means of escape: travel distances, stairs, detection and alarm.
- Stair, handrail and guarding details.
Completion certificate. Under regulation 17, it's given when the authority is satisfied, after taking all reasonable steps, that the requirements are met; GOV.UK says usually within 8 weeks of completion. It's "evidence (but not conclusive evidence)" of compliance. Keep it with the drawings: a landlord, buyer or insurer may ask for it.
What happens if a mezzanine goes in without building regulations approval?
Contravening building regulations is an offence under section 35 of the Building Act 1984. The authority can also serve a compliance notice, or a section 36 notice requiring the work to be removed or altered. Local authorities can give retrospective approval through regularisation.
- Prosecution (section 35). Penalties include a fine and, on conviction on indictment, up to two years' imprisonment.
- Compliance notice (section 35B). Specified steps within a set period. Ignoring it without reasonable excuse is a further offence.
- Removal or alteration (section 36). The owner can be required to remove the work or alter it to comply. If not done within 28 days, the authority can do it and recover the cost. This can't be used more than 10 years after completion.
Section 36 also protects you. Where full plans were granted by the building control authority and the work matches the approved plans (and isn't higher-risk building work), a section 36 notice can't be given for breaking building regulations. Build exactly what was approved.
Regularisation. GOV.UK says a local authority (not a private approver) can give retrospective approval for work done without consent after 11 November 1985. You may have to open up and alter the work first.
Is building regulations approval the same as planning permission or a fire risk assessment?
No. Building regulations cover how the work is built. Planning permission is a separate system and you might need both. Your fire risk assessment is an ongoing duty that must be reviewed when the premises change.
Planning. GOV.UK says building regulations approval is different from planning permission, and you might need both. Check planning with your local planning authority before you commit.
Fire risk assessment. Under article 9 of the Regulatory Reform (Fire Safety) Order 2005, the responsible person must make a suitable and sufficient fire risk assessment, record its findings and review it regularly, particularly when the premises undergo "significant changes, extensions, or conversions". A new mezzanine is that kind of change. Building control approves the design; your assessment covers how the floor is actually used, stocked and kept clear, and whether staff know the way out.
How are mezzanine floors regulated in Wales, Scotland and Northern Ireland?
Wales uses the Building Regulations 2010 with its own Welsh Approved Documents. Scotland requires a building warrant before work starts. Northern Ireland has the Building Regulations (Northern Ireland) 2012, approved by the district council.
Everything above describes England. Check the detail with your local building control office.
Wales. The Building Regulations 2010 apply in England and Wales, with separate Welsh versions of many provisions. The Welsh regulation 12 has the same full plans rule for premises covered by the Fire Safety Order. The Welsh Government publishes its own Approved Documents, including Approved Document B for buildings other than dwellinghouses, so use those. GOV.UK confirms registered building control approvers operate in Wales too.
Scotland. Section 8 of the Building (Scotland) Act 2003 requires a building warrant for construction work on buildings the regulations apply to, unless they exempt it. Working without one, or not in line with it, is an offence. Local authorities act as verifiers: they grant the warrant and accept the completion certificate. Guidance is in the Scottish Government's non-domestic technical handbooks.
Northern Ireland. The Building Regulations (Northern Ireland) 2012 apply. The Department of Finance says you must first seek approval from your district council to erect, alter or extend a building, and the council enforces the regulations. Guidance is in the Technical Booklets.
What should you ask a mezzanine supplier about building regulations?
Ask who applies and to whom, whether the design relies on the raised storage concession, how escape and stairs meet the guidance, and who gets the completion certificate.
- Who applies, and is the fee included? Local authority or registered approver?
- Which fire route? The 7.7 concession, or fire protection? If the concession, what changes if people later work up there?
- Is it a storey? Is the deck more than half the area of the space?
- Escape: travel distance from the furthest point, and how many stairs.
- Stairs and edges: BS 5395-3 or BS 4211, and 1100 mm guarding at floor edges.
- Slab: who confirms it can take the base plate loads?
- Handover: drawings, calculations, load notice and completion certificate.
A mezzanine built among racking means the racking needs checking too: include both in your racking inspection, and treat racking changes for the new layout like any other pallet racking alteration.
Related guides
Mezzanine floor building regulations: frequently asked questions
Do mezzanine floors need building regulations approval?
In practice, yes. A new floor inside a building affects structure, fire safety and escape, which makes it building work. If you're unsure, GOV.UK says to check with a building control body.
Can I use a building notice for a warehouse mezzanine?
Not in England or Wales. Regulation 12(3) of the Building Regulations 2010 requires full plans for building work in premises covered by the Regulatory Reform (Fire Safety) Order 2005, which includes warehouses.
Does a storage mezzanine need fire protection?
Not always. Approved Document B paragraph 7.7 allows a single-tier, storage-only floor without the normal fire resistance if it meets every condition, including few people, no public, open above and below, compliant escape and size limits.
How big can a mezzanine be without fire protection?
Not more than 10 m in width or length and half the floor area of the space. With fire detection to BS 5839-1 on the lower level, up to 20 m. With sprinklers throughout, no size limit is set.
How far can people walk to an exit from a mezzanine?
For normal hazard storage, Approved Document B allows 25 m where escape is in one direction only and 45 m where there's more than one. Higher hazard storage is 12 m and 25 m.
How high does mezzanine edge guarding need to be?
Approved Document K gives 1100 mm for edges of floors in factories and warehouses, and 900 mm for stairs and ramps.
Can a private company sign off my mezzanine?
Yes, in England and Wales. You can use a registered building control approver instead of the local authority. They give the council an initial notice and set their fees with you.
What if our mezzanine was installed without approval?
The authority can prosecute, serve a compliance notice, or require the work to be removed or altered. You can apply to the local authority for regularisation, but may need to alter the work.
Do I need a building warrant for a mezzanine in Scotland?
The Building (Scotland) Act 2003 requires a building warrant for construction work on buildings covered by the regulations, unless they exempt it. Apply to your local authority before starting.
Sources
We checked the facts on this page against these sources on 12 November 2026:
- The Building Regulations 2010, regulation 3 (meaning of building work)
- The Building Regulations 2010, regulation 12 (building notice or full plans)
- Fire safety: Approved Document B (GOV.UK)
- Protection from falling, collision and impact: Approved Document K (GOV.UK)
- Building regulations approval: how to apply (GOV.UK)
- Building Act 1984, section 36 (removal or alteration of offending work)
- Building (Scotland) Act 2003, section 8 (building warrants)