Read the Rating Before the Racks Go Up
Direct answer: A mezzanine is planned around two different numbers: uniformly distributed load in kN/m² for the deck, and point load in kN at each rack footplate. Racking converts a spread load into concentrated point loads, so a deck rated for storage on paper can still be overloaded by a rack layout that misses the primary beams.
Two numbers that get confused
Mezzanine decks are rated for distributed load, usually quoted in kilonewtons or kilograms per square metre, and separately for point loads under each support. Pallet racking on a mezzanine concentrates weight into column feet, so the point-load figure is often the binding limit.
Before installing racking on a deck, compare each rack leg's maximum load against the deck's point rating at that position, not just the total.
Habits that overload decks
Full pallets parked temporarily in aisles, liquid totes stacked two-high in one zone, and forklift traffic never designed for the deck all push loads past the plan. Mark rated zones on the floor and keep stacked storage inside them.
Re-check the plan whenever the layout changes; a deck rated for shelving may not be rated for racking.
Design load vs point load on a mezzanine deck
| Term | What it means | How it is usually expressed | What to check |
|---|---|---|---|
| Uniformly distributed load (UDL) | Load spread evenly over the whole deck area | kN/m² or kg/m² | Racking leg loads convert to concentrated loads — a UDL figure alone is not enough |
| Point / concentrated load | Load applied at one spot, e.g. a racking footplate | kN over a defined bearing area | Footplate size and whether spreader plates are needed |
| Racking load path | How rack leg loads reach the mezzanine primary beams | kN per leg, per position | Legs must land on or near primary beams, not mid-span of a secondary beam |
| Live load allowance | People, trolleys, pallet trucks moving on the deck | kN/m² reserved on top of storage load | Whether the storage layout leaves room for traffic |
| Deflection limit | How much the deck sags under load | L/xxx ratio or mm | Deflection affects racking plumb and forklift operation |
FAQ
What does 5 kN/m² mean in practice?
It is a distributed rating of roughly 500 kilograms per square metre, but only when spread evenly. A single heavy item in one spot uses point capacity, not the area figure.
Can mezzanine ratings be upgraded later?
Sometimes, by adding support columns or reinforcement under rated positions, but it needs an engineer's review and new documentation, not guesswork.
Do I need approval to put racking on a mezzanine?
In most jurisdictions the load plan must be reviewed when the use changes. Confirm with the deck supplier and keep the revised drawings on file.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.