Retaining walls and inground tanks

When you're installing a retaining wall or inground tank, you’ll need to think about things like surcharge and where your wall or tank will be placed in relation to a building or other structure.

A surcharge is the vertical pressure applied to the ground surface near the retaining wall. It can include extra loadings such as fences and driveways. This surcharge load will add to the horizontal pressure on the retaining wall. If these pressures aren’t factored in, there is a risk your wall or tank will collapse.

We advise that you consult a qualified professional like a structural engineer to help you understand the surcharge load for your site conditions.

If you’re putting your wall or tank near a building or other structure, there are rules around distances and wall height. There are also rules for when you're proposing to build a retaining wall on a boundary. This is to ensure support for neighbouring sites, and that future development has been considered.

Our guidance for retaining walls and inground tanks gives more detail:

Guidance for retaining walls and inground tanks(PDF, 202KB)

Apply for building consent

In some situations your retaining wall may be exempt from building consent

If your land is zoned residential

If your wall does not retain more than 1.5 metres (vertically) of ground and includes groundwater drainage, it may meet criteria to be exempt from building consent.

Government guidance: Retaining walls up to 1.5 metres depth of ground

If your land is zoned rural

If you’re in the rural zone, you can build a retaining wall up to 3 metres high, if it has been designed or reviewed by a chartered professional engineer. You all must also be suitably distanced from the boundary or existing buildings.

Government guidance: Retaining walls up to 3 metres depth of ground