The Signs a Retaining Wall Is Failing

Retaining walls almost always give warning before they fail. The problem is that the warnings look like cosmetic defects, and the wall stays standing for long enough that people stop noticing.

The useful thing is that the pattern of movement tells you the cause, which tells you whether you are looking at a drainage retrofit or a rebuild.

Lean

A wall leaning outward uniformly, with the top further out than the base and the face still straight, is being pushed. That is pressure behind it, and in this climate that means water. The wall itself is intact; the load has exceeded what it was designed for.

A wall rotating at the base, where the whole wall including the bottom course has tipped forward, points at the footing rather than the pressure. The footing is not holding it, either because it was undersized or because the ground under it has given way.

Bulge

A wall true at both ends with a belly in the middle of a span means the elements spanning between the posts are carrying more than they can. On a sleeper wall that means the sleepers are too thin for the post spacing, or the posts are too far apart for the height. It is a design issue rather than a ground issue.

Cracking

On a block wall, a stepped crack running diagonally up through the joints means the wall is being bent and has insufficient reinforcement to take it. A vertical crack in a straight line, often at a change of height or where two sections meet, is a movement or settlement joint doing its work or a place where one was needed and not provided.

Fine surface cracks in render are usually cosmetic. Cracks you can see daylight through are not.

Soil coming through the face

Material washing out between sleepers, through joints, or out of weep holes means the filter layer has failed or was never installed. Water is moving through the wall and taking the bank with it.

The wall may look fine for years while this continues. What it produces is a void behind the wall, and eventually the ground above drops.

Ground dropping behind

A lawn or a garden bed sinking behind a wall that appears sound is one of the more serious signs, because it means material has already left. Paving lifting or dropping at the edge nearest a wall is the same story.

Water where it should not be

Water seeping through a wall face is normal on a sleeper wall and expected. Water pooling at the base of a wall after rain and staying there means the outlet is not working. Weep holes that never run when everything else is soaked means they are blocked.

What to do about it

None of these are usually emergencies. A wall that has been at the same lean for ten years is behaving differently to one that moved last month, and the rate of movement matters more than the amount. Take a photo now and another after the next serious rain.

What is urgent: any wall that has moved suddenly, any wall supporting a structure, driveway or pool that is showing movement, and any wall where the ground above it has cracked along a line parallel to the wall.

Read retaining wall repairs, or call 0468 066 055 and describe the movement.