After the recent rain, plenty of backyards across South East Queensland are showing the damage: soil slumping off a slope, garden beds washed onto the lawn, or an old timber wall starting to lean. The good news is that many of these problems can be fixed with a simple sleeper wall you can build yourself over a day or a weekend.
This guide walks you through what to think about before you start, the sleeper and post options that suit DIYers, and the drainage that stops the next storm undoing your hard work.
Before you start: is this a DIY job?
A weekend wall is perfect for low garden beds, edging and gentle slopes. Before you buy anything, take a walk around the area and think about these things.
Height. Low walls, around knee height, are the sweet spot for DIY. They're quick to build and need less heavy-duty materials. Taller walls hold back a lot more weight and usually need engineering and council approval, so leave those to a professional.
Slope. The steeper the ground behind your wall, the harder the soil pushes on it, especially when it's wet. On a gentle slope, a single low wall does the job. On a steeper block, a couple of short terraced walls stepped up the hill are often easier to build than one tall one.
What's above the wall. Look at what sits uphill. A driveway, shed, pool, fence or house adds a lot of extra load, and that's a job for a pro. Also check where water comes from in a storm: roof runoff, downpipes or a neighbour's yard can all end up behind your wall.
What's below the wall. Think about where the water will go once it gets through. You don't want to send runoff onto a path, under your house slab or into your neighbour's yard. Check for underground services before you dig too.
Trees and plants. Vegetation works both ways. Established plants and groundcovers above and below a wall help hold soil together after rain, so keep what you can. But large trees close to the wall can push posts out of line as their roots grow, and digging through big roots can harm the tree. Leave room for roots, and plant low groundcovers on the finished slope to help stop it washing out again.
If in doubt - get a professional out to take a look!
Pick your sleepers
For a weekend build, the best sleeper is the one you can comfortably carry and place. Having said that, it's a balance of "do it right" vs "get it done". If a job calls best for a heavier sleeper, then trying to get it done with anything less is just extra work down the track.
Here's how the main options compare for DIYers.
Treated pine: the lightest, cheapest and easiest to cut. Best for quick garden beds and edging (although take care with veggie gardens due to the timber treatment). Choose pine treated for in-ground use, and expect to replace it sooner than other options.
Hardwood: heavier and tougher than pine, with a rich natural colour that suits a rustic garden. It costs a bit more than pine, but gives you a solid, natural-looking wall. Like all timber, it will eventually break down in wet ground.
Concrete: the longest-lasting option and the best in wet ground. Choose plain grey, or black patterned sleepers for a sharp, modern look. Concrete is heavy, so line up a helper, plan your access and have them delivered close to where you're building.
Composite: light enough for one person to carry, and won't rot, rust or attract termites. A great match for soggy spots and a quick weekend build. We stock two composite systems:
- SuperSleeper: a full composite wall system with matching posts and caps. It cuts with a circular saw and comes with a 35-year warranty.
- TuffPoly: timber-look composite sleepers that weigh under 10kg each, so no heavy lifting.
H posts and C posts: the easy way to build
H and C posts make a sleeper wall far more DIY-friendly. You set the posts, let the concrete go off, then slide the sleepers in. No bolting or fiddly fixings.
The posts need to match your sleepers:
- Concrete, pine and hardwood use galvanised steel posts. The post channel has to suit the sleeper's thickness, so tell us which sleepers you're using and we'll match the posts.
- SuperSleeper and TuffPoly each come with their own matching composite posts. Use those rather than steel posts.
- H posts go along the straight run of the wall. Each sleeper slides down between two posts and sits in their channels.
- C posts go at the ends, giving you a neat finish where the wall stops. Some can be paired to turn a corner.
You can also go the traditional route and use a hardwood post cut to height to go alongside your timber sleeper wall.
Two things worth knowing:
- With all-timber walls the sleepers go on the uphill side of the posts. The soil pushes the sleepers against the posts instead of trying to pull them off the screws.
- The posts are usually the first thing to rot, because they’re buried in wet ground. That’s why a lot of people now pair timber sleepers with galvanised steel H and C posts. You get the timber look and no rotting posts, and it’s the quicker DIY build.
The key to a good-looking wall is getting the posts straight, level and evenly spaced. Run a string line, check each post with a spirit level as you go, and follow the sleeper maker's guide for spacing and how deep to set them. A rapid-set concrete like Easy Mix Rapid Set sets quickly, which keeps a weekend build moving. Just follow the directions on the bag for setting times before you load up the posts.
Drainage and geofabric: what the rain taught us
If the recent rain showed anything, it's that water does the damage, not the soil. Wet soil is much heavier than dry soil, and if water can't escape from behind a wall it pushes until something gives. A lot of leaning or failed walls come down to poor drainage.
The good news is that drainage is simple and cheap to add while you build:
- Ag pipe (slotted drainage pipe) along the bottom of the wall carries water away.
- Geofabric wraps the gravel or lines the soil behind it, so dirt can't wash in and clog the drainage over time.
- A clear outlet gives the water somewhere safe to go, away from your house and your neighbours.
Geofabric is a permeable fabric that lets water through but holds soil back. It costs little and keeps your drainage working for years. Placed behind the sleepers, it also stops soil washing through the gaps in a heavy downpour.
Your weekend plan at a glance
Every yard is different, but a simple low sleeper wall usually follows this rhythm:
- Plan and gather. Check the height, slope and what's above and below. Measure up, then grab your sleepers, posts, concrete, ag pipe, gravel and geofabric in one trip.
- Mark out. Peg the line of the wall and run a string line.
- Set the posts. Dig the holes, stand the posts, check them with a level and concrete them in.
- Slide in the sleepers. Once the concrete has set, drop the sleepers in from the bottom up.
- Drain and backfill. Lay geofabric, ag pipe and gravel behind the wall, then backfill with soil.
- Finish and plant. Tidy up and plant groundcovers to help hold the soil before the next storm.
Grab everything in one trip
Sleepers, H and C posts, concrete, ag pipe and geofabric are all on the shopping list for a weekend wall. Come and see our team in Caboolture and we'll help you work out what you need for your yard. Call us on 07 5499 0344 or browse the range at fenceworld.com.au.
This article is general information only and isn't engineering or building advice. Every site is different. Always follow manufacturer instructions, check with your local council, and get professional advice for taller walls or walls supporting structures, driveways or steep slopes.