Warehouse Mezzanine Floor Regulations: Planning, Building Control and Safety
Short answer: in England a warehouse mezzanine almost always needs building regulations approval, because it is a new floor with its own structure, fire and escape, guarding and access requirements. It usually does not need planning permission if it is entirely inside the building, unless the building is used for retail and the mezzanine adds more than 200 m² of floorspace, or the planning permission for the site restricts it.
A mezzanine looks like the cheapest square metre you'll ever buy. It often is, as long as it's designed for the loads, cleared by building control, and doesn't break the fire strategy of the building it sits in.
This guide explains the rules that apply in England, where Craftex works, from the contractor's side of a warehouse fit-out. It covers planning, building regulations, fire, structure, guarding, access and the practical checks before you order steel.
Planning permission: usually not, with exceptions
Under the Town and Country Planning Act 1990, works that affect only the interior of a building are generally not "development", so they don't need planning permission. A mezzanine inside an existing warehouse usually falls into that category.
The exceptions to check:
- Retail use. Article 44 of the Town and Country Planning (Development Management Procedure) (England) Order 2015 brings internal works back into planning control where they increase the floor space of a building used for the retail sale of goods (other than hot food) by more than 200 m². That catches trade counters and retail warehouses.
- Planning conditions. Many industrial and retail warehouse permissions carry conditions limiting floorspace or preventing mezzanines. Read the decision notice for your unit.
- External changes. New windows, roof lights, louvres or plant on the outside need to be checked separately.
- Change of use. If the mezzanine is for offices, showroom or other uses that change how the building is used, the use itself may need checking.
If you lease the unit, the landlord's consent is a separate question. Most industrial leases treat a mezzanine as an alteration needing a licence. See our guide to the licence for alterations.
Building regulations: yes, almost always
A mezzanine is new structure and a new floor that people use, so it is building work under the Building Regulations 2010. Because warehouses are workplaces covered by the Regulatory Reform (Fire Safety) Order 2005, regulation 12(3) requires a full plans application to building control (local authority or registered building control approver) rather than a building notice.
The main requirements that apply:
| Requirement | What it covers on a mezzanine |
|---|---|
| Part A: structure | Design of the deck, beams, columns and connections for the intended loads; the existing slab under each column |
| Part B: fire safety | Means of escape from the mezzanine, fire resistance of the structure, fire detection and alarm, separation from other parts of the building |
| Part K: protection from falling | Guarding to open edges, stairs and handrails, loading points |
| Part M: access | Whether and how the mezzanine must be accessible, depending on its use |
| Part L | If you add lighting, heating or ventilation on or under the mezzanine |
Fire safety: when a mezzanine becomes a storey
Approved Document B Volume 2 (buildings other than dwellings) calls a mezzanine a gallery: a floor or balcony that doesn't extend across the full footprint of the building and is open to the floor below. Two definitions decide a lot:
- In most buildings other than assembly buildings, a gallery is counted as a storey if its area is more than half that of the space it projects into.
- The building is treated as multi-storey if there is more than one gallery and their total area is more than half the floor area of the space.
Crossing those thresholds changes escape and fire resistance requirements. Other points from the guidance:
- Fire resistance of the structure. Gallery structures are elements of structure and should have the fire resistance set out in Appendix B. Even in a single-storey building, where most elements of structure may not need fire resistance, an element that supports a gallery does.
- Exclusions. Loading galleries and galleries provided only for maintenance and repair are excluded from the definition of an element of structure.
- Escape. People on the mezzanine need a safe route out within acceptable travel distances, which can mean a second stair on a large deck.
- Detection and alarm. A mezzanine can hide a fire starting below it or create an area people don't regularly visit. Detection may need extending under and on the deck.
- Sprinklers. If the building has sprinklers, the area under the mezzanine will normally need protection too. Check with your insurer and sprinkler maintainer before you design.
Fire resistance is often provided by a fire-rated ceiling under the deck and protection to columns. Design it in from the start: it affects headroom, lighting and the racking beneath.
Structure and loads
Most mezzanine problems are structural, and most of them are predictable.
- Define the use. Storage, picking, offices and plant all have different design loads. A deck designed for light offices is not a storage floor.
- Check the slab. Each column puts a concentrated load into the existing floor slab. Ask your engineer to check the slab and, if needed, use base plates or new pads.
- Rack-supported or freestanding. Rack-supported mezzanines use the racking as structure; freestanding ones stand on their own columns. Both work. The choice affects flexibility later.
- Load notices. Display the safe working load on the deck, and keep the design information in the building's health and safety file.
- Industry guidance. The storage equipment industry and HSE's warehousing guidance (HSG76) cover design, installation and inspection of storage structures.
Guarding, stairs and loading points
Under the Workplace (Health, Safety and Welfare) Regulations 1992, employers must take measures to prevent people falling a distance likely to cause injury. In building regulations terms Part K covers guarding and stairs. In practice:
- full-height guarding to all open edges, typically 1100 mm high in buildings other than dwellings, with no gaps a person or goods could fall through;
- stairs with handrails, designed for the people and loads that will use them;
- pallet gates at loading points, so the edge is never open while goods are placed on the deck;
- kick plates or mesh where small items could fall onto people below.
Access: does the mezzanine need a lift?
It depends on what the mezzanine is for. A storage deck used only by trained staff is treated differently from offices, meeting rooms or staff welfare facilities that employees and visitors need to reach. Discuss the use with building control early, and remember your duties under the Equality Act 2010 sit alongside Part M.
Business rates and the lease
A mezzanine adds usable floor area, which can increase the rateable value of the unit. Ask your surveyor before you commit if rates matter to your budget. At lease end, your landlord may want it removed, so check the reinstatement terms (our dilapidations guide explains why that matters).
Working in a live warehouse
Most mezzanines go into warehouses that can't stop. That means planning the steel delivery and erection around operations, segregating the work zone, and sequencing noisy and overhead work for quieter periods.
Our own warehouse jobs show the pattern. At the Banbury warehouse we created a new 148 sq m area for welfare and storage in four weeks while the warehouse kept running, including a storage room with pallet racking and metal safety barriers. At a 120 m² warehouse in Hackney with 6 m ceilings, we redesigned and installed the engineering systems, including electric heating, bespoke lighting and a pumped drainage system for a sink and emergency safety shower where there was no natural outflow. And at Drake's railway-arch warehouse, where nothing could be drilled into the structure, we built a fully self-supported internal structure. Each of those constraints is the kind a mezzanine design has to answer before steel is ordered.
A mezzanine checklist
- Define the use and loads (storage, picking, offices, plant).
- Check the planning permission and conditions; confirm the 200 m² retail rule doesn't apply.
- Get landlord consent if you lease.
- Survey the slab, columns, headroom, sprinklers, lighting and racking.
- Decide the fire strategy: storey or not, escape, fire resistance, detection.
- Design guarding, stairs and pallet gates.
- Agree access requirements with building control.
- Submit a full plans application.
- Plan installation around live operations.
- Keep the design, load notices and certificates with the health and safety file.
For broader warehouse planning, see what a warehouse fit-out involves and our guide to warehouse layout design and planning.
