Top Retaining Walls Christchurch builds gabion retaining walls across Christchurch. A gabion is a wire basket packed tight with rock, and a row of them works as a gravity wall. The face is permeable, so water runs through instead of banking up behind, and that single property removes the most common cause of wall failure.
Every other wall type fights water. You build a drainage layer, run a coil, wrap it in geotextile and hope nobody blocks the outlet in fifteen years. A gabion wall has no back face to push against. Water arrives at the rock, moves through the voids, and comes out the front.
We still put a drainage layer and geotextile behind a gabion wall, because we do not want fine soil washing into the rock over time. But the wall is not relying on that system the way a timber or block wall is.
| Baskets | Galvanised or PVC coated welded mesh |
|---|---|
| Rock | Angular graded rock, commonly 100mm to 200mm |
| Source | Canterbury quarries, short cartage to most sites |
| Facing | Visible faces hand packed, centres machine filled |
| Drainage | Permeable by design, plus geotextile behind to stop silt ingress |
| Movement | Flexes rather than cracks, suits liquefaction prone ground |
| Coastal | PVC coated mesh recommended near New Brighton and Sumner |
Gabion rock needs to be angular and hard so the pieces lock against each other. Canterbury supplies it well. Quarries around Teddington and Oxford produce graded basalt suited to gabion work, and it is a short truck run to most Christchurch sites.
We hand pack the visible faces so the rock sits flat and tight with no gaps, then machine fill the middle. A hand faced gabion looks completely different to one that was tipped full, and the difference is labour, not materials.
A gabion wall is flexible. If the ground settles a little the baskets deform slightly and the wall carries on holding. A rigid wall in the same situation cracks. On land with a liquefaction history, which covers a lot of eastern Christchurch and Kaiapoi, that tolerance is worth having.
The wire is the part that decides the life of the wall. We use galvanised or PVC coated mesh, and near the coast at New Brighton or Sumner the PVC coating is worth the extra because salt air attacks bare galvanising.
Moss and small plants colonise the face, particularly on the shaded south side. Most owners like it. If you do not, keep the face in sun and clear it occasionally.
You can also plant into the top course or run a soil filled cell along the front. Gabions take that well because they drain so freely.
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.
The wall itself drains through the face, so hydrostatic pressure is not the problem it is with other walls. We still lay geotextile behind to stop fine soil washing into the rock over the years.
The rock lasts indefinitely. The wire is the limiting factor, so mesh coating decides the life. PVC coated mesh outlasts bare galvanised, especially in salt air near the coast.
Around New Zealand they usually sit in a similar band to block per lineal metre. The labour of hand packing the faces is the main cost, so a long straight wall prices better per metre than a short fiddly one.
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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