Top Retaining Walls Christchurch builds concrete sleeper retaining walls in Christchurch, the system that uses galvanised steel H posts with reinforced concrete panels dropped down between them. It looks like a timber sleeper wall from a distance and behaves like a concrete one, which is the whole point.
The posts are hot dip galvanised steel with a channel on each side. We set them in concrete footings, then slide reinforced concrete panels down the channels one at a time. The soil pushes the panel into the channel, so there is nothing to pull loose.
There is no timber anywhere in the structure, which means nothing rots. On a wall that is going to sit against wet ground for its whole life, that is a straightforward advantage.
| Posts | Hot dip galvanised steel H section, set in concrete footings |
|---|---|
| Panels | Steel reinforced concrete, slid down the post channels |
| Footprint | About 100mm at the post, the slimmest of any wall type |
| Rot risk | None, there is no timber in the structure |
| Finishes | Plain, rock face or moulded timber grain |
| Speed | A straight run can be panelled in a day once footings cure |
| Height | Consent and engineering above 1.5m or with a surcharge |
A steel post is around 100mm wide. A 200mm timber pole is twice that, and a block wall needs a footing wider still. On a narrow side boundary in Riccarton or Addington, where there is only a metre between the house and the fence line, those millimetres decide whether the job is possible.
The panels also stack fast. A straight 15m run can go from bare footing to finished wall in a single day once the concrete has cured.
Panels come plain grey, in a rock face texture, and in a moulded timber grain. The timber look panels give you the appearance of a sleeper wall with none of the maintenance, which is popular on new builds where the landscaping has to look finished on handover day.
Plain panels take paint or plaster if you want them to disappear behind planting.
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.
Up front, yes. Over the life of the wall they usually work out cheaper, because there is nothing to rot and nothing to replace.
Not really. The panels are straight and slide into straight channels. A curve has to be built as a series of short straight runs with a post at each change of angle.
Yes, exactly the same as any other wall. Water pressure does not care what the wall is made of. We build the metal, coil and geotextile layer before backfilling.
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.
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