Top Retaining Walls Christchurch builds concrete crib retaining walls in Christchurch for banks that suit a gravity solution. Crib walls use interlocking precast concrete units laid in alternating tiers and filled with granular drainage material, and the weight of that fill is what holds the ground back.
The first stretcher course goes on a concrete foundation or a well compacted base, set to establish the batter. From there the headers and stretchers alternate up the wall, forming open cells, and we backfill each layer with granular drainage material as the wall rises.
The finished wall leans back into the bank at around one in four. That lean, plus the weight of the fill, is the whole structural idea. There are no deep posts and no reinforcing steel running into the soil behind.
| Units | Precast concrete headers and stretchers |
|---|---|
| Batter | About one in four backward lean |
| Base | Concrete foundation or compacted granular base |
| Fill | Granular drainage material placed in layers |
| Front cells | Soil filled and planted where you want a green face |
| Best for | Wide banks, variable ground, terraced solutions |
On a site where the ground below is variable, or where machine access makes deep post holes difficult, a crib wall spreads its load over a wide base instead of relying on individual footings. Terraced crib walls also let you handle a tall bank as several short walls.
MBIE guidance uses exactly that example. Three 1.2m crib walls with enough horizontal separation that no wall loads the one below can avoid consent entirely, where one 3.6m wall could not.
Fill the front cells with topsoil and plant them, and within two or three seasons the concrete largely disappears. Trailing and creeping species work best. This is a common approach on rural boundaries and larger sections around Yaldhurst, West Melton and Tai Tapu.
Precast units also age well. There is no timber to rot and no coating to peel.
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.
Yes, particularly on larger sites and rural boundaries. They spread load over a wide base and give you a plantable face, which suits banks where a hard wall face would look out of place.
Sometimes. Each wall has to retain 1.5m or less and the horizontal separation has to be enough that no wall imposes a surcharge on the one below. We work that out on site and tell you honestly whether the geometry allows it.
Granular drainage material, not site spoil. The fill is structural. Filling cribs with clay or topsoil at the back is how these walls fail.
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.
