An intermediate floor in a warehouse, often supported by pallet rack uprights, increasing usable cube.
Detailed Definition
A mezzanine is a raised platform built inside a building, between the main floor and the roof, to add working or storage area without expanding the footprint. Warehouse mezzanines come in three main types: free-standing structural steel mezzanines on their own columns, rack-supported mezzanines that use pallet rack uprights as columns with storage below, and shelving-supported mezzanines built on multi-level shelving. They are used for picking, packing, offices and light storage, and are reached by stairs, with materials moved up by lifts, conveyors or forklifts through pallet gates.
Design and permitting questions
A mezzanine is a structure, so it usually needs engineered drawings, a building permit and inspection. Designers work from a floor live load rating, often expressed in pounds per square foot, plus point loads from carts, pallet jacks or heavy shelving. Rack-supported designs must also account for the rack's own load and, in many areas, seismic forces. Fire code questions are common: added floor area can affect sprinkler design, egress and whether sprinklers are needed under the platform.
Safety features to plan for
- Guardrails on open sides; OSHA's walking-working surfaces rules generally require fall protection at unprotected edges 4 feet or more above a lower level.
- Pallet drop areas protected by safety gates that keep one side closed while the other is open.
- Posted load capacity signs.
- Stairs with handrails and adequate lighting.
- Column protection where forklifts work near supports.
Never place pallets on a mezzanine that was not rated for them, and keep forklift traffic away from the columns or protect them with column protectors. Re-check the rating before changing how the space is used, for example converting light storage to pallet storage.
Related Glossary Terms
Frequently Asked Questions
Do warehouse mezzanines need a building permit?
In most US jurisdictions, yes. A mezzanine adds floor area and structural load, so local building departments typically require engineered plans, a permit and inspections, and the fire marshal may review sprinkler coverage and exits. Requirements vary by location and by how the space will be used, so contact the local building authority and use a mezzanine supplier that provides stamped engineering for your site.
Can pallets be loaded onto a mezzanine with a forklift?
Yes, if the mezzanine is rated for the pallet loads and has a designed pallet drop area. These areas use pallet safety gates that close the edge toward the workers on the mezzanine while open to the forklift, then swap. Check the floor's rated capacity against the heaviest pallet and any equipment such as pallet jacks used on the deck, and post the rating where operators can see it.