A couple in Porirua rang me last winter after the bank behind their garage slumped in the rain and left a slip of clay sitting against the block wall. Same first question everyone asks: what’s a retaining wall going to cost us?
I do gardens up in Rotorua, not big structural retaining walls, but between my own sites and the Wellington builders I’ve worked alongside over the years, I’ve stood on enough hill sections — from Karori and Khandallah down to Porirua’s Elsdon and Titahi Bay — to know the honest answer isn’t a number off the top of your head. It depends on the height, the ground, and whether you need a consent. Here’s how I’d walk you through it over the fence, because the figure people quote you before they’ve seen the site is almost never the figure they end up paying.
Height, load, and ground: what really sets the price
A retaining wall isn’t priced off a chart per metre. Three things move the number more than anything else:
- Height. Under about a metre is a different job to a two-metre wall holding back a Porirua hillside. Load goes up fast with height, and so does cost.
- What it’s holding. A wall carrying a driveway or a house above it — engineers call that a surcharge — has to be built heavier than one holding back a garden bed.
- Access and ground. Wet clay, a steep site, no room to get a digger in — each one adds hours. Wellington’s hill sections tick all three boxes at once, and a lot of them were cut into the hillside long before today’s drainage standards existed.
What I’d budget for a Wellington retaining wall in 2026
These are rough Wellington-region figures, supplied and built, GST included, for a straightforward site. Treat them as a starting point for a conversation, not a quote:
| Wall type | Height | Cost per m² (incl. GST) |
|---|---|---|
| Timber pole wall | Under 1m | $450–$750 |
| Timber wall, engineered | 1m–1.5m | $750–$1,100 |
| Concrete crib or block wall | Any height (more on a hard hill site) | $900–$1,600 |
| Engineer’s design + producer statement | Where required | $2,500–$6,000 |
So a modest 8-square-metre timber wall might land around $6,000 to $9,000, while a serious engineered hillside job can easily run past $30,000. That spread is real, and anyone who quotes you a firm price without walking the site is guessing.
Consent — the step people skip
This is the one that catches Porirua and Wellington homeowners out. A retaining wall generally needs a building consent once it’s over 1.5 metres high, or lower than that if it’s carrying a load like a driveway or a building above it. On some clay hillsides the council will also ask for geotechnical input before they’ll sign off. Get the consent step wrong and you’re into retrospective consent, which costs a lot more than doing it properly the first time. The rules are set out plainly on the government’s Building Performance site, and I’d read them — or ring Wellington City or Porirua City Council — before you sign anything.
Drainage behind the wall matters just as much as the wall itself in our wet winters. A wall that can’t shed water will eventually push over no matter how well it was built, and I’ve gone into why in a separate piece on why hillside drainage matters in wet Wellington winters.
Timber or concrete on a hill section
For a low garden wall, treated timber is cheaper and sits at home on a bush section. For anything holding a real load, or where you want to stop thinking about it for 50 years, a concrete crib or poured wall wins. H5-treated timber poles will give you 30-odd years in Wellington ground if the drainage behind them is right — skip the drainage and you’ll be redoing it in 15. On a hill section I almost always steer people towards the engineered option, because a wall failure on a slope doesn’t just take the wall — it takes the garden, the fence, and sometimes the neighbour’s patience with it.
Getting quotes you can actually compare
Get three quotes, all pricing the same height, materials, and drainage — otherwise you’re comparing apples with kūmara. Ask exactly what’s included: excavation, cartage of spoil, drainage metal and pipe, and the backfill. Cartage of wet clay off a Porirua site is a genuine cost people forget to ask about. And make sure the quote states who’s arranging the consent and the engineering, because that responsibility falling through the cracks is where jobs go sour.
Questions I get asked on site
Do I need consent for a retaining wall in Wellington or Porirua? Generally yes if the wall is over 1.5 metres high, or lower if it carries an extra load like a driveway, house, or another wall above it. Check with Wellington City or Porirua City Council, or the Building Performance site, before you start.
How much does a retaining wall cost per square metre in 2026? As a Wellington-region guide including GST, expect roughly $450 to $750 per square metre for a low timber wall, and $900 to $1,600 per square metre for concrete, with engineered hillside walls costing more again once you add design and a producer statement.
Timber or concrete for a Wellington hill section? Timber’s cheaper and fine for low garden walls, but for anything holding a driveway or house, or on a steep slope, an engineered concrete wall lasts longer and is the safer call.
Can I repair a leaning retaining wall, or do I need to rebuild it? If the lean is new and traces back to a blocked drain, fixing the drainage can sometimes be enough to stop it moving further. But once the timber’s rotten or the wall has shifted more than a little at the top, patching it is a false economy — you’re better off pricing a full rebuild against the repair before you spend money twice. A second opinion on that call is cheap — a Wellington retaining wall builder can usually tell from the drainage outlets whether the lean has stopped.