The structural performance of a warehouse floor depends entirely on correct slab thickness and reinforcement. With constant forklift traffic, pallet racking point loads, and tight operational tolerances, under-specifying the slab leads to costly repairs and long-term failure. This guide explains how to choose the right slab depth, sub-base structure, and reinforcement method for different warehouse use cases — from standard logistics to heavy industrial storage.
Start with a detailed load assessment. Identify the heaviest forklift in use and note axle weight, tyre type, and turning radius. For racking, calculate the total unit weight per leg. Use this data to determine both uniformly distributed and concentrated loads. Slabs subject to narrow aisle vehicles or counterbalance trucks will need increased thickness and better edge protection. Assume 10,000+ repetitions per day in active zones for industrial distribution centres.
For general-purpose warehouses, slab thickness is typically 150 mm. For heavy forklift use or narrow aisle racking, increase to 175 mm or 200 mm. For high-rack logistics centres or cold stores with point loading, 225 mm to 250 mm is standard. The slab must distribute load without cracking or deforming at joints or mid-span. Follow TR34 guidance for UK designs, or reference ACI 360R in international specs. Slab-on-grade designs must consider sub-base stiffness.
No slab thickness or steel will compensate for a weak base. The sub-base should be 150 mm to 300 mm of compacted Type 1 or MOT stone, with a blinding layer and DPM membrane on top. In poor ground, increase thickness or use geogrid stabilisation. Avoid soft spots and ponding. The base must be level, drained, and load-bearing before pour begins. Moisture barriers are critical under warehousing with sensitive racking or coatings.
Traditional reinforcement uses A193 or A252 steel mesh placed mid-slab. This controls cracking but adds joints and labour. Fibre-reinforced slabs use macro-synthetic or steel fibres to disperse stress and often eliminate mesh. Hybrid systems combine mesh and fibre for jointless designs. Choose reinforcement based on slab size, shrinkage strategy, and surface loading. Steel fibre slabs are ideal in logistics and ambient distribution due to reduced joint count and lower shrinkage cracking.
Where joints are needed, use dowelled construction joints and sealed saw cuts. Joints must be placed to minimise risk under high loads — never beneath racking legs or in forklift brake zones. For heavy traffic, consider armoured joints or leave joints out entirely using a jointless slab system. Load transfer at joints is critical. Dowels, key joints, or aggregate interlock must prevent vertical deflection under repeated impact.
Mesh must sit in the top third of the slab, supported by chairs, not dropped in during pour. Poor placement is a common cause of early cracking. For fibre slabs, confirm mix ratios and placement technique match supplier guidance. Vibrate the concrete correctly and finish consistently to avoid weak zones. Use laser levels or screeds to maintain accurate thickness across the slab. Surface flatness and strength both depend on uniform pour control.
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