Article summary
Practical and compliance considerations when topping a retaining wall with a fence.
- Category:
- regulations
- Read time:
- 4 min
- Published:
- 9 April 2025
- Written by:
- My Homes Fencing Expert
Quick answer: putting a fence on top of a retaining wall changes both the engineering and the consent picture. The retaining wall may need building consent (in Auckland, retaining over about 1.5m generally does, and lower if it carries extra load like a fence or driveway), and the combined height of wall plus fence can push past the 2m mark where a fence would otherwise be exempt. The two also can't just be bolted together casually — the wall has to be designed to take the fence's load.
Wall-and-fence combinations are common on Auckland's sloping sections, but they're one of the easiest fencing jobs to get wrong on compliance. Here's what to know before you build.
As the fencing division of a full construction company, we handle exactly these combined jobs regularly.
How the Consent Rules Change
A fence on its own up to 2m is usually exempt building work, and a low retaining wall on its own may be too — but combine them and the thresholds shift. A retaining wall generally needs building consent once it's over about 1.5m high, and that trigger drops lower when the wall also carries a 'surcharge' load such as a fence, a driveway or a structure above it. The fence's load is exactly that kind of surcharge.
On top of that, the combined height of the retaining wall plus the fence sitting on it is what matters for the fence height rules — so a 1m wall with a 1.8m fence reads as a 2.8m structure, well over the 2m exempt limit. This catches a lot of homeowners out, which is why we check the numbers and overlays before quoting a wall-top fence.
The Engineering: Loads and Drainage
A retaining wall that was designed to hold back soil isn't automatically designed to also carry a fence and the wind load that comes with it. Mounting a fence on or immediately behind a wall adds force the wall may not have been engineered for, so the wall's design has to account for it — often meaning the posts are engineered into the wall structure, or set back from it, rather than simply fixed to the top.
Drainage is the other critical piece. Retaining walls live or die on drainage, and adding a fence must not block the weep holes and drainage that stop water building up behind the wall. Done poorly, a wall-top fence can trap water and shorten the wall's life or, worse, contribute to failure.
Getting It Done Right
Because a combined wall-and-fence involves structural loads, drainage and often consent, it's not a DIY-friendly job or one for a fencing-only operator who won't look at the wall side. The wall and fence need to be considered together from the start — height, loads, footings, drainage and the paperwork.
As the fencing division of My Homes Construct Ltd, we can assess the retaining and fencing together, tell you honestly whether consent is required, and build it so the wall carries the fence safely for the long term. If you're planning a fence on a slope or on top of an existing wall, get it checked before you commit.
Frequently Asked Questions
Often yes. A retaining wall generally needs building consent over about 1.5m, and lower when it carries extra load like a fence. The combined height of wall plus fence also counts toward the 2m fence limit, so a wall-top fence frequently needs consent even when a standalone fence wouldn't.
Not safely without checking. A wall designed to hold back soil isn't automatically built to carry a fence's weight and wind load. The posts usually need to be engineered into or set back from the wall, and the fence mustn't block the wall's drainage.
For the height rules, it's generally the combined height of the wall plus the fence — so a 1m wall with a 1.8m fence is treated as a 2.8m structure, over the 2m exempt limit. That's why these combinations so often need consent.
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