Shipping Container Foundations in NZ: Pads, Piers and Sleepers

A shipping container used for storage does not need much underneath it. It needs firm, level ground that keeps the floor dry and lets the doors open and close properly. The container carries its weight through the four corner castings, so what matters is solid support at those corners. In a 2014 determination about two 20ft containers on sleepers, MBIE found that “Shipping containers are inherently stable even when empty” and did not consider that foundations are required “for a shipping container simply placed”.

That changes once the container becomes permanent, is fixed down, stacked, joined to a roof or fitted out for people. At that point the foundation becomes building work, it usually needs engineering design, and consent questions follow. This guide covers the common bases, how to level and drain them, tie-down for wind and earthquake, and where the consent line sits.

Gravel pad

A compacted gravel pad is the most common base for a storage container on a section or farm. Strip the topsoil, lay and compact a granular base slightly larger than the container footprint, and level it. A 20ft container is about 6.06 m by 2.44 m outside, so a pad of around 7 m by 3.5 m leaves room to step around it. Adding pavers, concrete blocks or sleepers on the gravel under each corner keeps the steel floor frame off wet stones and makes final levelling easier. Gravel drains well, which suits wet NZ winters, and the container can be lifted off again later with no trace beyond the pad.

Timber sleepers

Sleepers are quick and cheap. Lay two treated timber sleepers across the width at each end so they sit under the corner castings, levelled on firm ground. On soft ground under a 40ft, an extra pair at mid-length can help stop the long floor frame settling, but the corner castings carry the load. Use ground-contact treated timber, check it every few years and replace it if it starts to rot. MBIE’s 2014 determination dealt with exactly this set-up, and found that placing containers on sleepers was not building work.

Concrete pads, piers and piles

Precast concrete pads or blocks under the four corners give a durable, level base for a storage container and stay clear of rot. Simply placed, they are no different from sleepers. Once you form a foundation and fix the container to it, it becomes building work. Invercargill and Grey District councils both list a formed foundation or slab with hold-down fixings as a trigger for building consent, and Whangārei District Council states that foundation work is building work.

For permanent, habitable or raised containers, the usual approach is concrete-filled holes or piers with steel plates cast in, welded or bolted to the corner castings. Ruapehu District Council’s guidance on converting a container to a habitable space requires “permanent, earthquake resistant foundations” and gives an example of 6 to 8 piles in 900 mm deep concrete-filled holes with the container securely fastened. Expect specific engineering design. Timber piles built to NZS 3604 are designed for timber-framed floors, not for the point loads under container corners, and an MBIE determination from 2024 shows councils look hard at pile design on poor or filled ground.

Strip footings and slabs

Strip footings run as continuous concrete beams under the long sides or ends of the container. They suit sloping sites, joined containers and workshops where the load from racking or machinery needs to spread. A full concrete slab makes sense when the container is part of a larger floor, for example two containers either side of a covered workspace, or a container garage. Both are building work, and both should be designed by an engineer who knows the container’s corner load paths. If you are planning a container shelter between two containers, the foundation and the roof are usually designed together.

Levelling and drainage

• Level across the width so the doors hang true. A container set out of level can twist slightly and the doors may bind or fail to seal.
• Check the corners with a long level or a laser and adjust with packers before the truck leaves, while the container can still be lifted.
• A very slight fall along the length helps rainwater run off the roof instead of ponding, which slows corrosion. Keep the doors workable.
• Keep the base above the surrounding ground so water drains away, not under the container. Gravel around the base helps.
• Leave an air gap under the floor. It helps keep the floor timbers dry.

Tie-down for wind and earthquake

A loaded storage container on level ground is heavy and stable, which is why MBIE accepted an unsecured placement in 2014. Councils still raised the lack of anchoring in that case, and engineered hold-downs are expected when the container is habitable or occupied, stacked or raised, on piles, or on an exposed site, especially if it may sit empty.

NZS 3604 sorts sites into wind zones L, M, H, VH and EH; sites above EH need specific engineering design, as BRANZ explains in its guide to wind zones. Earthquake zones run from 1 to 4. You can look up indicative wind, earthquake and exposure zones for any address on BRANZ Maps, which gives your engineer a starting point. On coastal sites the fixings matter as much as the foundation: in exposure zone D, which covers land within 500 m of the coast and all offshore islands, NZS 3604 requires structural fixings other than nails and screws to be stainless steel of at least grade 304. Our coastal corrosion guide explains the zones.

When a foundation makes it building work

Council guidance from Invercargill and Grey District uses almost the same words: placing or moving a shipping container on a property is not building work. A container used for storage with no formed foundation or slab needs no building consent. Once you add a formed foundation or slab with hold-down fixings, services, a roof or an internal fit-out, consent comes into play, unless the work fits an exemption in Schedule 1 of the Building Act.

• Clause 3 covers detached buildings up to 10 m², such as a 10ft container of about 7.3 m². Since 23 October 2025 there is no boundary distance condition for these.
• A 20ft (about 14.8 m²) or 40ft (about 29.7 m²) falls in the 10 to 30 m² band. Clauses 3B (design or construction by a licensed building practitioner) and 43 (prefabricated design reviewed by a chartered professional engineer) are the more defensible routes for containers, with a 1 m boundary distance. Clause 3A relies on lightweight building products and is a questionable fit for a steel container.
• None of these exemptions allow sanitary facilities, and sleeping is allowed only in limited cases.

Exempt work must still comply with the Building Code, and district plan rules still apply. Habitable containers need building consent and permanent foundations. Read our guides to building consent for shipping containers, container sleepouts and shipping container homes before you design the base. Our Australian site compares the foundation types for shipping containers with photos; the NZ consent rules above still apply.

Before the container arrives

Build and level the base before delivery, and make sure the truck can reach it. A HIAB or swinglift can lower a container onto pads or piers precisely, while a tilt tray slides it off the back and suits gravel or sleepers better; see HIAB vs swinglift. Mark the corner positions, tell the supplier what base you have built, and check the delivery and site access guide. When the site is ready, request a delivered quote.