Retaining Wall Rebuild, Canford Cliffs

Why it failed

Two builders had already turned the job down before we looked at it. The wall was about 2.1m high, retaining a terraced garden on a steeply sloping plot, and it had moved roughly 90mm at the top.

When we dug an inspection pit at the base, the reason was immediately obvious. The foundation was a 300mm strip – nowhere near enough for the retained height – and there was no drainage of any kind behind the wall. Every time it rained, water built up in the ground behind and pushed. It had been pushing for about twenty years.

Doing it once

Patching a wall in this condition buys a few years and wastes the money. We had a structural engineer produce a design, took the wall down completely, and rebuilt it.

The new wall has a reinforced concrete foundation, a dense blockwork core with reinforcement running vertically into the foundation and horizontally in the bed joints, a land drain in free-draining stone behind it wrapped in geotextile, and weep holes through the face at 900mm centres. It is faced in reclaimed brick to match the house with a bullnose capping.

The drainage is the part nobody sees and the part that means it will still be standing when the house changes hands twice more.

The result

Four weeks, including two while we waited on the engineer’s design – which we would rather do than guess. The garden gained a usable second terrace, and the owners got a wall they will not have to think about again.