Top Retaining Walls Christchurch builds tiered retaining walls across Christchurch, and on a steep section this is often the smartest money you can spend. Instead of one tall engineered wall, you build two or three shorter ones with flat planted terraces between them.
The Schedule 1 exemption applies to a wall retaining 1.5m or less with no surcharge. Two 1.2m walls set far enough apart that neither loads the other are two exempt walls, not one 2.4m wall. MBIE guidance gives this exact example using three 1.2m crib walls on a terraced site.
The critical word is separation. If the upper wall is close enough that its retained soil pushes on the lower one, you have a surcharge and the whole thing needs engineering. The geometry has to be genuine, and we work it out on site rather than hoping.
| Typical setup | Two or three walls at 1.0m to 1.4m each |
|---|---|
| Separation | Enough that no wall imposes a surcharge on the one below |
| Consent | Can stay exempt when the geometry is genuine |
| Materials | Timber pole, Keystone block, crib or stone |
| Terraces | Planted, or used for steps and paths |
| Best for | Wide sections with room to step back |
| Not suited to | Narrow side boundaries and very steep ground |
You build more total wall length, so the material cost goes up. You avoid engineering fees, consent fees, producer statements and inspections, which on a tall wall commonly run into thousands before a single post goes in the ground.
On most Christchurch jobs in this range the tiered option comes out cheaper overall, and it finishes faster because there is no consent wait. We price both ways where the site allows it, so you can see the numbers side by side.
A 2.4m bank is dead space. Two 1.2m walls with a 2m terrace between them give you a planting bed at waist height, somewhere to put steps, and a way to get up the slope without a ladder of stairs.
On Port Hills sections through Cashmere, Huntsbury and Mount Pleasant we build a lot of these, because the loess ground suits shorter walls and the terraces catch and slow surface water instead of letting it run straight down the slope.
Narrow sections are the main limit. If you only have three metres between the house and the boundary, you cannot fit the horizontal separation the tiers need, and one engineered wall is the honest answer.
Very steep ground is the other. Past a certain slope the terraces become so narrow they stop being useful, and the total wall length gets out of hand.
Every wall we build gets drainage. At least 300mm of clean free draining metal, a perforated coil at the base running to a real outlet, and geotextile over the top so silt cannot block it. It is not an optional line on our quotes.
Often, once you count engineering and consent costs on the single tall alternative. We price both options where the site allows, so you can compare properly.
Far enough that the upper wall's retained soil does not load the lower wall. There is no single number, because it depends on wall height and soil. We assess it on site.
Yes, and you should. Planting holds the terrace soil together, slows surface water and makes the whole slope look intentional rather than cut.
Our old wall was rotten right through and leaning into the neighbour's place. They pulled the lot out, put proper drainage behind the new one and had it finished in three days. Swept the site clean every afternoon before they left too. Tidiest crew we have ever had here by a long way.
They sorted the consent, which was the bit I was dreading. Dealt with the council so I never had to, and kept me in the loop the whole way through. The driveway sits right above it and has not shifted a millimetre.
Steep section, shocking access, and they still made it look easy. They suggested two smaller walls instead of one big one, which saved us thousands in engineering fees. The terrace in between is now my favourite part of the whole garden.
Call [PHONE] or answer three quick questions. The site visit and the written quote cost you nothing.
