What we do

Retaining

Retaining walls in Dunedin

Dunedin is a hill city Most sections here have a slope on them somewhere, and a lot of them have clay underneath. That means retaining walls aren't a nice-to-have — they're how you get a flat bit of ground to actually use.

We build them across the city, from a low garden wall holding back a bank to engineered block walls with a consent and an engineer's design behind them.

Do you need a building consent

This is the first question people ask, and the answer catches a lot of people out.

Under the Building Act, a retaining wall is exempt from building consent only if both of these are true:

it retains no more than 1.5 metres of ground, measured vertically, and
it carries no surcharge

It's the second one that surprises people, mostly because nobody explains what it means.

A surcharge is extra weight sitting on the ground your wall is holding back.

The wall is built to resist the soil pushing against it. Anything sitting on top of that soil presses down, and that downward weight turns into extra sideways push against the wall. So the wall has to be stronger than the dirt alone would need it to be.

Easiest way to picture it: stand at the bottom of the wall and imagine a line running up and back at about 45 degrees. Anything inside that wedge is leaning on your wall, whether it looks like it or not.

So all of these count as a surcharge:

a driveway above the wall — a parked car is heavy, and a moving one more so
a shed, a garage, a deck or a pool close behind it
another retaining wall stacked above it
ground that keeps sloping up from the top of the wall, because that's simply more soil weight again
even a stockpile — a pile of firewood, soil or building material sitting there long-term

Which is how a wall that's only a metre high ends up needing a consent, an engineer and a design, when the identical wall on flat ground with nothing behind it wouldn't.

If your wall needs a consent, it needs an engineer's design too. We'll tell you straight which side of the line your job falls on when we come and look at it.

And if it does need one, you don't have to go and find an engineer. We have our own, we've worked with him for years, and we bring him in as part of the job. You get one person to deal with and one number to ring — not a contractor telling you to go away and organise a design before he can quote you.

That's most of the hassle of a consented wall gone, and it's the reason a lot of people end up ringing us for the tricky ones.

On a lifestyle block or rural section, the threshold can be higher — up to 3 metres where the wall is designed by a chartered professional engineer. Worth asking about if you're out of town, but confirm it with the council for your specific site rather than taking it as read.

The bit that catches people out: hazard land and Section 72

This one is worth knowing before you spend money, because almost nobody mentions it.

If the council considers your land is subject to a natural hazard — and on parts of these hills, land instability is exactly that — it can't simply grant a building consent as normal. It has two options. Either you make adequate provision to deal with the hazard, or the consent gets granted under Section 72 of the Building Act.

A Section 72 consent comes with a notice recorded against the property's title. It doesn't stop the work happening. But it stays on the record, and it's the kind of thing that comes up later when the property is sold or refinanced.

Why we're telling you this: because finding out at the wrong end is expensive and unpleasant. If your site is in an area with instability on record, that's worth knowing before you commit to a design, not after. We'll flag it if we see it, and we'll tell you when a job needs an engineer and a conversation with the council rather than a digger and a quote.

Engineered plans, consent application, we can cover it all. We've worked on enough of these sections to know the fasted route to your desired outcome.

The jobs other people turn down

Steep sections, tight access, no room to swing, everything in by hand — that's a lot of what we do.

We've done pours where every bucket of concrete was carried up the steps by hand, because there was no other way to get it there. We've built a ramp to get the machine up a driveway before the job could even start, because there was no way in otherwise.

That's usually why we get the call. It's also usually why somebody else didn't want it.

If your job is on an awkward bit of ground and you've had people not turn up to quote it, give us a call. We'll at least come and tell you honestly whether it can be done.

Slip repair and bank stabilisation

Sometimes the wall isn't the plan. Sometimes the bank has already come down.

We do slip remediation work — most recently on a section where a major slip put the top of the property on the back doorstep of the house. That job meant digging out the failed material, getting the bank back to stable ground, building an engineered retaining wall to hold it where it should be, and putting the drainage in behind it so water wasn't the cause a second time.

If a slip has come down on your place, the order of work matters. Clear it, find out why it moved, stabilise it properly, and only then think about the finish. Just carting away the mess and tidying up the face is money spent on the same problem twice.

We'll come and look and give you a straight answer. If it needs an engineer's eyes on it first, ours goes on it — that's part of what we do, not another job on your list.

The drainage bit nobody talks about

Most retaining walls that fail don't fail because the timber or the blocks weren't strong enough. They fail because water built up behind them.

Wet ground is heavy, and a wall designed to hold back soil can be pushed over by the weight of soil plus trapped water. On loess ground, water does something worse than add weight — it takes strength out of the material the wall is holding back.

So every wall we build gets drainage metal behind it, a drainage coil at the base, and somewhere for that water to actually go.

If you're getting quotes and one is noticeably cheaper, ask what's behind the wall. That's usually where the difference is.

How to tell if the wall you've already got is in trouble

If there's an existing wall on your place, these are the things worth walking out and looking at: It's leaning, or bulging in the middle. A wall that's moved once will move again.The ground behind the top has dropped or there's a gap opening up behind it.Cracks in the face that weren't there last year, or that get wider after heavy rain.Timber poles that have gone soft at ground level. That's where they rot first, and it's the part holding everything up.Water seeping through the face, or nothing ever coming out of the drainage outlet. Both are bad signs — one means water's finding its own way through, the other usually means the drain is blocked. Rust stains or bulging on a block wall, which can mean the reinforcing inside is corroding.None of these mean it's about to fall over tomorrow. All of them mean it's worth getting looked at, because a wall repaired early is a fraction of the cost of one rebuilt after it's failed — and a failed wall can take the ground around it with it.

The jobs other people turn down

Steep sections, tight access, no room to swing, everything in by hand — that's a lot of what we do.

That's usually why we get the call. It's also usually why somebody else didn't want it.

If your job is on an awkward bit of ground and you've had people not turn up to quote it, give us a call. We'll at least come and tell you honestly whether it can be done.

What actually drives the price

Nobody can price a retaining wall off a phone call, and anyone who tries is guessing. Here's what moves the number:

Height and length. The obvious one, but height matters more than length. Every extra course of blocks means more load, deeper footings, and stronger everything.

Access. This is the big one. If a truck and a digger can get to the wall, the job is straightforward. If everything has to be barrowed in, or carried, the labour goes up fast. We take on plenty of sites other contractors won't, but access has to be priced honestly.

Ground conditions. Dunedin clay and loess behave differently from fill or gravel. Soft ground means deeper holes or bigger footings. We allow for what we can see, and we tell you up front where there's a risk of finding something we can't.

Drainage. Not optional, and not the place to save money — see below.

Consent and engineering. If the job needs a consent, budget for the engineer's design and the council fees on top of the build.

Where the spoil goes. Every wall means digging, and everything that comes out has to go somewhere. On a tight site with no room to stockpile, that's truck movements, and truck movements are money. It's a line people forget until they see it.

What happens, start to finish

So you know what you're agreeing to:

We come and look. Free, anywhere in Dunedin. We'll walk the site, look at the access, look at the ground, and tell you what we think it needs.
You get a written quote. It's valid for 7 days, and it's the price we charge — we don't come back afterwards asking for more because the job took longer than we thought. If we hit something nobody could have known was there, that's covered in the variation terms and we'll talk to you before doing anything about it.
If it needs a consent, our engineer does the design. You're not organising that part — we are. The consent then has to go through the council before anything starts, and that takes time, so build it into your thinking rather than your deadline.
Setting out and excavation. Digging the footing or boring the pole holes, and getting the spoil off site.
The wall goes up. Poles and lagging, or footing, blocks and block fill depending on the design.
Drainage and backfill. Drainage metal, coil at the base, an outlet that goes somewhere sensible, then backfilled and compacted in layers.
We tidy up and get off your place. Site left clean.

Common questions

How long does a retaining wall take? A straightforward timber pole wall on a section we can get a machine onto is usually a matter of days. Add difficult access, bad weather or a consent and it stretches. We'll give you a realistic timeframe when we quote, not an optimistic one.

Can you build in winter? Yes, though Dunedin weather and short days slow things down, and saturated ground can make excavation and compaction harder. Some jobs are better waiting. We'll tell you if yours is one of them.

Do I need an engineer? If the wall retains more than 1.5 metres, or carries a surcharge, or your land has instability on record — yes. But it's not something you have to go and sort out. We have our own engineer and we bring him in as part of the job, so you're not chasing a design around before anyone will quote you.

Can you match an existing wall? Usually. Bring us a photo. If the existing wall is old or moving, it's worth checking whether extending it is actually the right call.

Do you do small jobs? Yes. A low garden wall is a real job and gets quoted like one.

How much does a retaining wall cost in Dunedin? Honest answer: it depends on height, length, access, ground and whether it needs consent — and those vary so much between sections that any number on a web page would be misleading. That's why the on-site look is free. It's the only way to give you a figure that means anything.