Yes. In England a new mezzanine floor in a warehouse, factory or shop almost always needs Building Regulations approval, because it adds floor area and changes how the building performs on structure, fire escape and access. Planning permission is a separate question and is usually not needed for internal works, except in retail buildings where the extra floor space is more than 200 m².

This guide explains which parts of the regulations a mezzanine touches, what building control normally asks to see, and where the planning rules differ. It is written for England. Wales, Scotland, Northern Ireland and Ireland run their own systems with similar aims, so check with the local building control body before you order steel.

Does a mezzanine floor need Building Regulations approval?

A new mezzanine is building work, so approval is needed before the floor is put into use. Regulation 3 of the Building Regulations 2010 defines building work to include the erection or extension of a building and any "material alteration". An alteration is material if it would make the building fail, or fail more badly, against the requirements for structure (Part A), means of warning and escape (B1), internal fire spread in the structure (B3), external fire spread (B4), fire service access (B5) or access and use (Part M) (legislation.gov.uk, Building Regulations 2010, reg 3).

A mezzanine affects nearly all of these at once. It puts new loads into the floor slab, it creates an upper level that people must escape from, it can block sprinkler or detector coverage below, and it can change who can reach which part of the building. That is why building control officers treat even a modest storage platform as a project that needs drawings and calculations, not as furniture.

Approval comes from a building control body: either the local authority building control team or a registered building control approver for work that is not in a higher-risk building (GOV.UK, Building regulations approval). For a warehouse or factory mezzanine, the usual route is to submit plans and supporting calculations before work starts, then arrange site inspections, then receive a completion certificate.

Which Approved Documents apply to a mezzanine?

Four Approved Documents cover most of what a mezzanine has to satisfy. The Approved Documents are statutory guidance: you can meet the regulations another way, but you would then need to show building control that your solution performs as well.

Approved Document	What it covers on a mezzanine	What building control usually asks for
A: Structure	Deck, beams, columns, bracing, baseplates and the existing floor slab	Structural calculations, load rating, slab check under baseplates
B: Fire safety	Means of escape, fire resistance of the structure, detection and alarm	Escape route plan, stair positions, fire protection specification
K: Protection from falling	Edge guarding, stairs, landings, loading points	Handrail heights, stair geometry, pallet gate details
M: Access and use	How people, including disabled people, reach and use the floor	Statement on access, especially for office or public use

Lighting, ventilation and electrical work under the deck may raise further points, particularly if the floor will hold offices. Your designer should list every item in the application rather than leave building control to find gaps on site.

Fire safety: escape, fire resistance and detection

Fire safety is usually the part that decides cost, and it turns mainly on how the floor will be used. Approved Document B Volume 2 covers buildings other than dwellings and defines a gallery as a floor or balcony that does not extend across the full footprint of the building and is open to the floor below (GOV.UK, Approved Document B). A warehouse mezzanine normally falls within that description.

Approved Document B contains specific provisions for galleries and raised storage areas, including conditions under which the supporting structure does not need full fire resistance. Whether your floor meets those conditions depends on its size relative to the room, whether people work on it, and the escape distances. As a rule of thumb, a floor used only for storage and visited occasionally is treated more lightly than one holding offices, packing benches or picking staff. Ask your designer to state the intended use clearly in the application, because changing a storage deck into a workspace later can make it non-compliant.

Typical fire measures building control may ask for

• Fire-resisting column casings and a fire-rated ceiling or fascia below the deck.
• Escape stairs placed so that travel distances to an exit stay within the Approved Document B limits; large floors often need a second stair.
• Extension of the existing fire alarm and detection under and over the deck.
• Sprinkler extension where the building is sprinklered, because a solid deck shadows the heads above.

Your fire risk assessment under the Regulatory Reform (Fire Safety) Order 2005 must also be updated once the mezzanine is in use. That is a duty on the person responsible for the premises, separate from building control approval.

Edge protection, stairs and loading points (Part K)

Every open edge of a mezzanine must be guarded, and the heights are set out in Approved Document K. For factories and warehouses with light traffic, Diagram 3.1 gives a minimum guarding height of 900 mm for stairs and ramps and 1,100 mm for landings and edges of floors (Approved Document K, Diagram 3.1). For industrial stairs, ladders and walkways, Approved Document K refers to BS 5395-3, the code of practice for industrial type stairs.

Loading points are the awkward area. Approved Document K accepts that guarding is not required in places such as loading bays where it would obstruct normal use, but it says alternative safeguards should be provided and agreed with the building control body (Approved Document K, paragraphs 3.1 and 4.4). On a mezzanine that usually means a pallet safety gate that keeps one barrier closed at all times while pallets are placed or removed. Our mezzanine pallet safety gate is designed for this job and can be specified with the deck.

The Work at Height Regulations 2005 apply as well, because anyone working near an open edge is working at height. HSE's guide to working at height explains the duty to prevent falls where people could be hurt (HSE, INDG401).

Structure and floor loading (Part A)

Part A requires the mezzanine to carry its own weight and the imposed load from people and goods safely, without overloading the existing building (GOV.UK, Approved Document A). In practice building control wants three things: calculations for the steelwork, a stated load rating for the deck, and evidence that the slab can take the point loads from the column baseplates.

The slab check is often forgotten. A mezzanine that is comfortably rated on paper can still punch through a thin or cracked slab under its columns. If the slab details are unknown, a core sample or a slab survey by an engineer is cheaper than relocating columns later. Larger baseplates can spread the load, but only the engineer can confirm they are enough.

The rating itself should match how the floor will be used, with a margin for later changes. Our guide to mezzanine floor load ratings in kN/m² explains how ratings are chosen and why an office deck and a pallet storage deck are designed very differently. The rating should then be shown on a notice at the stair head so staff know the limit.

Access and use (Part M)

Part M is about making buildings usable by everyone, and it becomes relevant when a mezzanine is a material alteration. A storage-only deck reached by staff who handle stock is usually viewed differently from an office or showroom floor that visitors or employees with mobility needs will use. Approved Document M Volume 2 covers buildings other than dwellings (GOV.UK, Approved Document M). If the floor will hold offices or meeting rooms, discuss access with building control early, because adding a platform lift after the steel is fixed is far harder than allowing space for one in the layout.

Do you need planning permission for a mezzanine?

Usually not. Under section 55(2) of the Town and Country Planning Act 1990, works that affect only the interior of a building, or that do not materially affect its external appearance, are not "development", so they do not need planning permission. Article 44 of the Development Management Procedure (England) Order 2015 makes an exception: where the building is used for the retail sale of goods (other than hot food), internal works that increase floor space by more than 200 m² do count as development (legislation.gov.uk, SI 2015/595, article 44).

Planning can also come back into play if the project changes the outside of the building (new windows or roof lights), changes its use, affects a listed building, or adds traffic and parking demand. Lease terms are another check: many industrial leases restrict structural alterations, so landlord consent may be needed even when the council is not involved.

How approval works in practice

A smooth project follows the same order every time. First, settle the use, size and load rating of the floor. Second, have the design checked against the slab and the fire strategy. Third, submit the application with drawings and calculations. Fourth, install, with building control inspections at agreed stages. Last, collect the completion certificate and update the fire risk assessment.

We make structural mezzanine floors in our own factory and send each quote with a layout drawing. The load data for each component comes with the order, so the engineer preparing the building control submission has what they need. You can see the range on our mezzanine floors page, and our article on what drives the cost of a mezzanine floor explains how fire protection and stairs affect the budget.

Frequently asked questions

Can I install a mezzanine without telling building control?

No. A mezzanine is building work under regulation 3 of the Building Regulations 2010, so it needs approval. Unapproved work can lead to enforcement, problems with insurance, and difficulty when you sell or sublet the building.

Is a storage-only mezzanine exempt from Building Regulations?

No. A storage-only floor still needs approval. What changes is the level of fire protection: Approved Document B treats some storage galleries more lightly than floors where people work, provided the size and escape conditions are met.

What height do mezzanine handrails need to be?

In factories and warehouses, Approved Document K gives a minimum of 1,100 mm at landings and floor edges and 900 mm on stairs and ramps. Guarding is normally completed with a mid-rail and kick plate.

Does a mezzanine affect business rates?

It can. The Valuation Office Agency's Rating Manual tells valuers to record mezzanine floors, their area and, where possible, their load capacity when inspecting factories and warehouses, so adding one may change the rateable value. Ask a rating adviser before you commit.

Sources

• legislation.gov.uk: The Building Regulations 2010, regulation 3 (meaning of building work)
• GOV.UK: Fire safety, Approved Document B
• GOV.UK: Protection from falling, collision and impact, Approved Document K
• GOV.UK: Structure, Approved Document A
• GOV.UK: Access to and use of buildings, Approved Document M
• GOV.UK: Building regulations approval
• legislation.gov.uk: Development Management Procedure (England) Order 2015, article 44
• HSE: Working at height, a brief guide (INDG401)
• GOV.UK: Rating Manual, factories, workshops and warehouses