Why Is My Retaining Wall Leaning After the Storms?

In this post:

• Why retaining walls move after heavy rain
• The warning signs to look for
• How to tell a repair from a rebuild
• What a properly built wall has behind it

Every wet season, our phone gets busier. People walk out after a big storm and notice the retaining wall isn't quite straight anymore. There's a lean. A crack. Soil spilling through a gap.

The first question is always the same. Can you just push it back?

Usually, the honest answer is no. And here's why.

It's almost always the water

A retaining wall holds back soil. Wet soil is much heavier than dry soil. During a big Brisbane downpour, the ground behind your wall fills with water and the pressure on the wall jumps.

If there's no proper drainage behind the wall, that water has nowhere to go. It just keeps pushing. Eventually the wall gives a little. Then a little more after the next storm.

Signs your wall is in trouble

• It's leaning forward, even slightly.
• There are new cracks, or gaps opening between sleepers or blocks.
• Soil or water is coming through the face of the wall.
• The ground behind the wall is sinking.
• Old timber sleepers or posts are soft or rotting.

Repair or rebuild?

A small problem caught early can sometimes be repaired. For example, a blocked drain that's cleared before the wall moves.

But if the wall is already leaning, straightening it without fixing the cause doesn't work. The water is still there. The wall will move again, usually within a season or two.

If the posts have rotted, or there was never any drainage, the right answer is normally a rebuild. That's frustrating to hear, but it's cheaper than paying twice.

What a proper wall has

The part you see is just the face. What makes it last is behind it.

• A drainage pipe at the base, running to an outlet.
• Clean gravel behind the wall so water can get to the pipe.
• Fabric to stop soil clogging the gravel.
• Posts that won't rot. We use galvanised steel H-beam posts for sleeper walls.
• Engineering where the height or the load above it calls for it.

What to do now

If your wall has moved, don't wait for the next storm. Take a photo from the end of the wall, looking along it, so we can see the lean.

Send it to us. We'll tell you honestly whether it's a repair or a rebuild, and why.

Common questions

Can a leaning retaining wall be pushed back?

Rarely for long. Unless the drainage problem behind it is fixed, it will move again.

How much does a new retaining wall cost?

It depends on height, soil, drainage and access. As a guide, our concrete sleeper walls start from around $800 to $1,200 per lineal metre, confirmed after a site visit.

Does a retaining wall need an engineer?

Walls around 1 m and higher usually do, and anything over 2 m also needs council approval. We organise both.

Keep reading

• The part of your fence you'll never see matters most
• My yard is hard to get into. Will that cost me more?
• Will the price change after I pay the deposit?

Worried about your retaining wall? Call us on 07 2141 7748, get a price online or let's have a chat.