Container Flooring

Two numbers govern floor loading. The concentrated limit: the forklift axle of the ISO 1496-1 type test — 7,260 kg (3,630 kg on each of two wheels) since the standard’s Amendment 3, 5,460 kg (2,730 kg a wheel) in the 1990 text older boxes were built to (the amended figure as IS 13288 Part 1, India’s identical adoption of ISO 1496-1, prints it; the 1990 one as ISO 1496-1:1990 and the CTU Code do). The test wheels are 180 mm wide and 760 mm apart, each on a 142 cm² footprint (per ISO 1496-1:1990). Either axle comfortably covers a compact warehouse forklift carrying a full pallet. The distributed limit is simply the payload: spread across the floor, a 20 ft box takes 28,250 kg. 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 quarantine borders, the ply is usually treated against wood-boring insects, and the compound is not the same from one builder or one decade to the next. 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. Some bamboo floors carry no insecticide at all — the builder’s spec sheet or the floor’s data plate is where to look for 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 — is the dearest of the wood options, a whole floor of new ply plus the labour, 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 is the cheapest of the three and 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.