Mezzanine floor design
A mezzanine adds floor area inside a building you already have, but it puts new loads onto columns, foundations and the slab below. We design mezzanine floors that carry their intended use safely and satisfy Building Control, for clients across the UK.
Can a mezzanine sit on the existing warehouse floor?
Sometimes, but not always. The mezzanine columns concentrate large loads onto small base plates, and the existing slab may not be strong enough. We check the slab and, where it falls short, design pad foundations so the mezzanine is safe rather than assuming the floor will cope.
Designing the mezzanine structure
A mezzanine is a self-supporting steel deck that sits inside an existing building, usually on its own columns rather than hanging off the walls. The design starts with the imposed load, which is very different for a picking and storage floor, a general storage floor, a retail sales floor or offices. We take the correct imposed load from BS EN 1991-1-1 and its UK National Annex, add the weight of the deck and any partitions, and size the beams, joists and columns to BS EN 1993 to carry it with deflection kept within limits that protect the finishes.
The deck build-up follows the use. Storage mezzanines often use a chipboard or steel deck on closely spaced joists, while office and retail floors need a stiffer deck and attention to vibration, so the floor does not feel lively underfoot. We set the column grid to suit the layout below, keeping racking aisles and circulation clear, and we design the edge protection, stairs and any pallet gates as part of the same package.
Checking the existing building and slab
A mezzanine only stands up if the floor beneath it can take the new column loads, and this is the check that is most often skipped. Each mezzanine column concentrates a large load onto a small base plate, and the existing ground-bearing slab may not have been designed for it. We check the slab for punching and bearing under the base plates, and where it is inadequate we design pad foundations cut into the slab or a spread base to bring the pressure within what the ground can take.
We also confirm the mezzanine does not overload or destabilise the building around it. In a rented unit the landlord and Building Control will want proof the existing structure and slab can carry the addition, so we produce calculations that stand on their own. Where a mezzanine leans on or ties into the existing frame, we check that frame for the extra load rather than assuming it has spare capacity.
Fire, access and regulations
Once a mezzanine is more than a small proportion of the floor below, or is used as a workplace, fire and means of escape come into play. We coordinate the structural design with the fire strategy, which may call for fire protection to the mezzanine steel, protected stairs and a set travel distance to an exit, all of which affect the layout and the steel sizes. Getting the fire requirement clear early avoids reworking the structure later.
The calculations are prepared to the Eurocodes, the relevant UK National Annex and Approved Document A, and coordinated with the loading, access and edge protection the mezzanine needs to satisfy Building Control and the Workplace Regulations. We deliver a package the steelwork installer can build from and Building Control can approve, whether the mezzanine is a single storage deck or a multi-level pick tower.
What we check.
The points our calculations resolve for a project like this.
- Correct imposed load for storage, retail or office use to BS EN 1991-1-1
- Beam and column sizing with deflection and vibration controlled
- Existing slab checked for punching and bearing under base plates
- New pad foundations where the existing slab is inadequate
- Fire protection, protected stairs and escape where use requires it
- Edge protection, stairs and pallet gates designed as one package
From enquiry to sign-off.
Enquiry
Send drawings or describe the problem. We confirm the scope, the deliverables and a target timescale.
Information
We agree the survey, drawings or data we need and any site access required.
Engineering
Design, calculation or assessment to the relevant Eurocodes and UK National Annex.
Issue
A clear, defensible report or set of calculations, with assumptions and limitations stated.
Common questions
Can a mezzanine sit on the existing warehouse floor?
Sometimes, but not always. The mezzanine columns concentrate large loads onto small base plates, and the existing slab may not be strong enough. We check the slab and, where it falls short, design pad foundations so the mezzanine is safe rather than assuming the floor will cope.
What load should a mezzanine be designed for?
It depends on use. A general storage floor, a picking floor, a retail sales floor and offices each take a different imposed load from the Eurocodes. We design for the correct load for your use, which keeps the floor both safe and economical.
Does a mezzanine need fire protection?
It can. Once the mezzanine passes a certain size or is used as a workplace, the fire strategy may require protected steel, protected stairs and controlled escape distances. We coordinate the structure with the fire requirement so it is right from the start.
Do you design mezzanines in leased units?
Yes. We produce standalone calculations that prove the mezzanine and the existing slab and frame can carry the addition, which is what landlords and Building Control need. We work across the UK.
Related in commercial, industrial & agricultural structural engineering.
Tell us what you are building.
Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
Start a project