Retaining Walls on a Boundary

This is the question that causes the most trouble on suburban blocks, and most of the trouble comes from one incorrect assumption: that a retaining wall on a boundary works like a dividing fence.

The law here involves property law, the legislation covering dividing fences and neighbourly disputes, and building regulation, and how it applies turns on the specific facts of a wall and a title. Nothing below is legal advice. If a wall on your boundary is contested or expensive, get advice specific to your situation before committing.

A retaining wall is not a fence

Dividing fence legislation sets up a shared-cost arrangement for fences. Retaining walls are generally treated differently, and the assumption that a neighbour must contribute half is often simply wrong.

The distinction that usually matters is who the wall benefits and whose land it is supporting. A wall exists because the ground on one side is at a different level to the ground on the other, and how that difference came about tends to drive the answer.

Cut versus fill

Broadly, if one owner has excavated their land, removing support from the neighbour’s soil, the responsibility for retaining generally sits with the party who did the cutting. If an owner has filled their land, raising it above the neighbour’s, the wall holding that fill is generally theirs.

Where the level difference came from the original subdivision earthworks, which is the situation on most estate blocks, it is less obvious and depends on what was approved and what the titles and any easements say.

The practical point is that “it is on the boundary so we split it” is not a rule, and either believing it or refusing it can leave you badly out of pocket.

A wall supporting a neighbour’s land

If your wall supports your neighbour’s soil, you generally cannot simply remove it and leave their land unsupported, even if the wall is entirely on your property. Landowners have rights to support for their land in its natural state.

That cuts both ways: it constrains what you can do with your own wall, and it gives you standing when a neighbour proposes to do something that removes support from yours.

Sort this out first

Talk to the neighbour first. Not as a courtesy: as the cheapest possible risk management. A wall replacement that begins with an agreed scope is a construction job. One that begins with a surprised neighbour is a dispute that can stop work entirely.

Worth establishing in writing: where the boundary actually is, which is a survey question and frequently not where the existing fence sits; what is being built and how high; who is paying for what; and access, because building a boundary wall usually needs to happen from one side and it may not be yours.

Where it goes wrong most often

Building over a boundary because the existing fence was assumed to be on it. Removing an old wall without arranging temporary support. Raising ground level against a neighbour’s fence, which changes what that fence has to be. And starting work that requires access from next door without having asked.

If your wall sits on a boundary and needs work, ring 0468 066 055. We would much rather have that conversation before the quote than after the machine arrives.