What to put a shipping container on

20ft Used Shipping Container (8.5ft Tall) – Brick Red – Wind & Watertight Storage — tap to view20ft x 8ft x 8.5ft Tall – New Shipping/Storage Container – Wind and Watertight – Blue — tap to view

Why the base matters so much

All of the load goes through the corner castings — not the floor, not the walls. Put three castings on firm ground and one on soft fill and the whole box twists. The first thing you notice is the doors: they stop meeting cleanly, the locking bars need forcing, and eventually the seals stop sealing and water gets in. None of that is a fault in the container, and all of it is avoidable.

Level across the diagonals

Most people level end to end, check the bubble and stop. The measurement that matters is across both diagonals, because that is the plane the door frame sits in. Check corner to corner both ways and shim until both read true — while the truck and its lifting gear are still on site, not afterwards.

Timber sleepers

Hardwood sleepers under the corner castings are the quickest and cheapest base that actually works. Lay them on a prepared, compacted surface rather than straight onto grass, make sure they sit flat and bear evenly, and accept that timber is a wear item that wants checking every few years. For most storage applications this is entirely adequate.

Concrete pads and footings

Individual concrete pads under each casting, or a full slab, give the most stable and permanent result. They suit reactive clay, long-term placement and anything that will be modified or occupied. The pads need to be sized for the ground conditions and set so that all eight bear evenly — a pad that is five millimetres proud of the others does the same damage as a soft corner.

Compacted crushed rock

A compacted crushed rock pad spreads load, drains well and copes with soft or sandy ground. Strip the topsoil, compact the subgrade, then build up with angular crushed rock rather than rounded gravel, which rolls under load. Run the pad past the container footprint so the edges do not erode, and give it a slight fall so water runs away.

Drainage and airflow

Water sitting under a container corrodes the underside and the cross-members, where you will not see it until it is serious. Make sure the ground falls away from the unit, keep vegetation cut back so air can move underneath, and never bank soil or mulch against the side walls. Raising the unit even slightly on its bearing points does more for its lifespan than almost anything else.

Australian ground conditions

Reactive clay through much of Melbourne and Adelaide swells and shrinks seasonally and will move a container over a year. Sand in Perth and coastal areas does not support point loads and lets castings sink. Queensland and northern sites add flooding, which a buoyant container will float in. Match the base to the ground you actually have, and re-check the level after the first full wet-to-dry cycle.

When the base needs engineering

Everything above is for storage use. Once a unit will be occupied — a cabin, an office, accommodation — the foundation becomes a regulated matter requiring an engineered, approved design rather than a practical choice. Resolve it before the build is specified, because the foundation can change the unit.