Container Flooring

Two numbers govern floor loading. The concentrated limit: 5,460 kg on one forklift axle (two wheel contact patches) — the pass condition of the ISO 1496 type test, comfortably covering a compact warehouse forklift carrying a full pallet. The distributed limit is simply the payload: spread across the floor, a 20 ft box takes ~28 t. Trouble comes from neither, but from true point loads — machinery feet, jack stands, steel crate corners — which punch through ply that a forklift rolls over harmlessly. The fix is dunnage: timber under every concentrated foot.

Because container floors cross every quarantine border on earth, the ply has historically been treated against insects — basileum and radaleum are the compound names on older floor data plates, with various pyrethroids on newer ones. For cargo this is a non-issue. For conversions it is the reason the standard advice exists: do not put food in direct contact with an original container floor, and treat the ply as sealed-in rather than food-safe. Newer floors use milder compounds, and bamboo floors may carry no insecticide at all — the floor’s data plate or the manufacturer’s spec sheet states the treatment used.

Conversions have three standard answers. Ply swap: unscrew and replace the original panels with untreated marine ply — the clean-slate option for homes and food use. Epoxy coating: seal the existing ply under a continuous epoxy layer — the barrier approach, standard in cafés and workshops, keeping the original floor’s strength. Steel or aluminium overlay: sheet metal over the ply for washdown floors, ramps and heavy workshops. For plain storage, the original floor needs nothing at all.

The choice is condition-driven. A full ply swap — unscrew the original panels, fit new untreated 28 mm marine ply — runs roughly $1,000–2,000 in material and labour for a 20 ft, and is the right call when the floor is delaminated, chemically stained, or destined for food or living use. An epoxy coating over a sound floor costs about $200–400 as a DIY job: it seals treatment compounds and spill history under a continuous barrier while keeping the original ply’s full strength — the value option when the floor is structurally fine but its history is unknown. A steel overlay costs more than either, but it is the only durable answer for washdown environments — commercial kitchens, wash bays, wet workshops — where standing water would eventually destroy any wood floor beneath.

Walk the whole floor: soft or springy spots signal delamination — plies separating from moisture, the floor’s usual end-of-life failure. Dark stains mean spills of unknown chemistry; a floor-wide stain pattern is a reason to renegotiate or budget a ply swap. Check the underside too if the unit is on blocks: rusted cross-members sag, and the floor follows. The rest of the buying checklist — roof, doors, castings, CSC plate — is in the buying guide.