Scenic Rim Retaining Wall Builders000
Walls don't fail because the sleepers were wrong

Method

Water gets behind the wall and has nowhere to go. Everything else is a symptom.
Method

Walls don't fail because the sleepers were wrong

What actually happens

Soil behind a wall is heavier wet than dry, and clay swells when it holds water. A wall built to hold dry dirt is holding something quite different after a wet summer, and it's been holding it every summer since.

So the wall starts to rotate at the top. Sleepers bow between the posts. The ground behind it drops as material escapes through the gaps. Then one afternoon of heavy rain finishes it, usually taking a fence, a shed pad or half a driveway with it. That's the point a wall becomes a knock down and rebuild rather than a repair.

What goes in behind ours

  • Geofabric behind every wall
  • A 100 millimetre socked ag pipe, the size engineered concrete sleeper wall drawings specify
  • 20 millimetre recycled drainage gravel filling the space behind the sleepers, so water drops to the pipe instead of sitting against the wall

The tell

If a quote doesn't list the drainage item by item, ask what's going in behind the wall. Most of the rebuilds we do are walls that never had it.

Soil backfill holds water against the back of the wall, and that pressure is what pushes it over. The worst one we've replaced had no drainage, hand mixed concrete and small footings, and it cost its owners about $30,000 with the removal of the failed wall included. We see many like it, usually a year or so after they went in.

Drainage is the cheapest thing to leave out, it's out of sight the day the wall is finished, and it's the single biggest reason two quotes for the same wall are thousands apart.

Sources

  1. Capital Concrete Sleepers, engineer drawings and structural notes (May 2024)A 100 mm subsoil drain on walls designed to AS 4678
  2. Island Block, retaining wall design manualDrainage pipe not less than 100 mm

Keep reading

Questions

Not answered here? Call us on 0488 844 741.

The questions we get asked most

The ones we replace nearly always come down to the same three things: no drainage, hand mixed concrete, and small footings. A lot of them fail within a year or so of going in.

The worst one we've replaced cost its owners about $30,000 once the removal and disposal of the failed wall was included.

Soil holds water against the back of the wall, and that water pressure is what pushes walls over.

Gravel lets the water drop to the ag pipe and drain away. It's one of the cheapest things to leave out and one of the most expensive to put right later.

Water. Wet soil is heavier than dry soil and clay swells when it holds water, so a wall built to hold dry ground is holding something else entirely after a wet summer.

That's why our quotes list the drainage: geofabric, a 100 millimetre socked ag pipe and 20 millimetre drainage gravel behind the wall. If a quote you're holding only says "drainage", or doesn't mention it, ask what's going in.

29 people have written about what it was like, and they all write about the same things.

The thing people tell us most is that they can’t believe it’s only the two of us. After that, it’s how fast Jake works, how clean he leaves the site, and the quality of the wall.

Reviews published on Google. Names as the reviewers gave them.

Why people trust us with this

Jake has more than 12 years in the industry, and he and Brittany started the business in 2023.

Built with what the first one was missing

Piers drilled with the right auger for the job, 450 mm on some walls and 300 mm on others, then 32 MPa plant concrete, steel reinforced sleepers, geofabric, a 100 mm socked ag pipe and 20 mm drainage gravel.

Drainage behind the wall

Geofabric behind every wall, a 100 millimetre socked ag pipe, and the space behind the sleepers backfilled with 20 millimetre recycled drainage gravel.

Drainage under load

Geofabric, a 100 mm socked ag pipe and 20 mm drainage gravel. Water behind a loaded wall is what brings it down.

Jake builds it

The person who quotes your wall is the person who builds it, on site from about 6:30, with no crew you've never met.

QBCC licence 15049372 (Jacob Spriggs)

Next

Tell us about the block

Six short questions, about two minutes. Brittany calls you back, then Jake comes out and measures the wall. Quotes are locked for 30 days, and the price only changes if you ask for extra work and approve it first.

A long timber look concrete sleeper wall with steps, running along a slope

Talk to us about your wall

Six short questions, about two minutes. Your details come first, so if anything cuts out halfway we can still call you back.

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