Many Auckland homeowners often forget about consent until the blocks are on the pallet in their driveway. A low retaining wall at the back of a West Auckland section can appear to be a weekend project and so getting plans done could appear to be a waste of money. However, Auckland Council don’t care how casual your project was.
The 1.5m everyone talks about
Under the Building Act, a retaining wall is generally exempt from building consent if it retains no more than 1.5 metres of ground and does not support any surcharge.
The 1.5 metres is the depth of earth being retained by the wall. If the earth on the high side is higher than you originally thought or the wall is built into a slope, you’ll want to get your measurements accurate. Often walls that appear to be only a short height will be retaining more than you think.
Even a wall under that height can need consent if something is loading the ground behind it.
What is a surcharge?
A surcharge is anything extra on top of the earth that is being retained by the wall. This is commonly a driveway but can include parking pads, garden sheds with slabs, pools, another wall higher up the slope or just ground continually rising.
Often people will build a garden wall along a steep driveway in Titirangi or Glen Eden and think they’re okay as it appears to be a short facing. If the wall is supporting a car this is a surcharge and you’ll usually lose your exemption.
When it comes to uncertainty, always consider you might need a building consent.
You still need to follow the Building Code
Even if a retaining wall doesn’t require a building consent you need to ensure the wall meets the Building Code. This includes ensuring the wall can withstand any loads it will be subjected to such as the wet winter months in Auckland and clay underneath much of the city.
You could also need a resource consent for earthworks, distance from a boundary, overland flow paths or natural hazard overlays in the Auckland Unitary Plan. Building consents don’t necessarily mean you’re following the planning rules. It may be okay to have a building consent but not meet the planning rules.
Auckland Council have a practice note for retaining walls. You can also use their online decision making tool. Get in contact with the council to ensure you’re following the correct procedures.
Soil, drainage and surrounding structures
Other factors which also play a role in your retaining wall design include the type of soil, drainage and surrounding structures. Many sections in Auckland, especially Western sections and North Shore have clay which can move when it gets wet. A wall without proper drainage behind it can look great in March but will begin to lean by August.
Most likely you’ll want to get an engineer involved if the wall is over 1.5m, has a surcharge, close to a boundary or house, or if the ground is steep or unstable. Sometimes you’ll need an engineer for a shorter wall.
If you’d rather not guess then contact some retaining wall builders in Auckland. They’ll be able to come out and assess the slope, soil and what the wall is actually doing. Mr Singh Brick & Block Laying are an LBP company based in Sunnyvale and work on garden walls, driveway walls and slopes around the city.
Ask Council
Different properties on the same street can have different overlays, ground and an entirely different answer. Write down how high your retaining wall is, what is behind the wall, if it’s close to a boundary/building and if you’re cutting or filling. Contact Auckland Council or a designer who will sign off on your drawings.
If you’ve built a wall that requires a building consent and you haven’t got one, this can cause issues when selling, refinancing or claiming on your insurance. Not a pleasant experience to find out you should’ve asked earlier.
If you’ve started building without a building consent stop and get some advice. It’s often easier to sort out the paperwork whilst the work is being done.
Get the rules right, the blocks are easy.
If a contractor appears to be taking the building consent lightly, take it slow.
