Sleeper vs Steel Retaining Walls: Cost, Lifespan and Which to Choose
Sleeper vs Steel Retaining Walls: Cost, Lifespan and Which to Choose
Timber sleepers are the usual choice for a garden retaining wall. They’re cheap, easy to buy and most landscapers have built plenty of them.
Steel panels cost more, but they last longer with very little upkeep and take up far less room.
A 3mm steel wall leaves you 100mm to 200mm more usable ground on every terrace than a sleeper wall would. We make steel retaining walls, so we’re not neutral here. Sleepers are still the better buy for some jobs, and we say so where that applies.
Sleeper vs Steel Retaining Walls Compared
| Timber sleepers | Lux Unique steel panels | |
|---|---|---|
| Materials for a 5m wall, 400mm high | Roughly £250 to £300 | £567.60 |
| Lifespan | Around 15 to 20 years for treated softwood, 40+ for oak | Decades with no treatment, plus a 5-year warranty |
| Wall thickness | 100mm to 200mm | 3mm |
| Height | Up to about 1m as a DIY job | Panels from 200mm to 700mm as standard, taller on request |
| How it’s held up | Posts concreted into the ground | Bolted panels on a firm, level base, fixed down through holes in the base |
| Upkeep | Re-treat softwood every few years | Just a rinse once or twice a year to clear dirt |
| Curves | Only with sleepers stood on end | Curved sections available |
| Look | Natural timber | Rust-orange Corten, a powder-coated colour, or galvanised on request |
How Much Does a Retaining Wall Cost?
For a wall built by a landscaper, Checkatrade’s cost guide gives these installed prices per square metre of wall face. The figures date from May 2024, so allow for some rise since.
| Material | Installed cost |
|---|---|
| Gabion | From £240 per m² |
| Timber sleeper | From £245 per m² |
| Concrete criblock | From £260 per m² |
| Concrete | From £285 per m² |
| Masonry or reinforced block | From £320 per m² |
| Stone | From £395 per m² |
Steel isn’t on the list, and it’s missing from most other cost guides too. Our Corten panels are sold supply only, from £39 for the smallest to £354 for a 700mm by 2,000mm panel.
Sleeper vs Steel Retaining Wall Cost: A 5m Example
Take a 5m run of wall at 400mm high, built yourself. Gravel and membrane for drainage cost about the same either way, so they’re left out.
Sleepers. Two rows of 200mm sleepers make 400mm. Allow about five 2.4m sleepers for the wall and two more cut down for posts. Treated softwood sleepers cost around £30 to £36 each, and you’ll need postcrete and long timber screws on top. That comes to roughly £250 to £300 in materials.
Steel. Two 2,000mm panels and one 1,000mm panel at 400mm high cost £567.60 with bolts included, plus delivery.
On materials alone, sleepers cost about half as much. If you’re paying a landscaper, Checkatrade’s figure puts the sleeper wall at around £490 fitted. Steel panels go up faster because there are no posts to concrete in, so labour should be lower. Two people can usually put up a 5m run in a day, including levelling the base.
Low Cost Retaining Wall Options
Treated softwood sleepers are the cheapest way to hold back soil for most people. On a low wall of one or two sleepers the groundwork stays simple, which is why they’re so popular for quick fixes.
Concrete sleepers cost more than timber but won’t rot. They’re very heavy, so they’re rarely a one-person job.
Gabions come out cheapest on Checkatrade’s installed list. The wire cages are inexpensive, but filling them takes a lot of stone.
If the slope is gentle, you may not need a wall at all. Planting the bank thickly with ground cover holds the soil for a fraction of the cost.
Steel isn’t the budget option on materials. You pay more for a wall that lasts longer and takes up less room, which the rest of this guide covers.
Sleeper Retaining Walls: Pros and Cons
Most people choose sleepers on price. They’re stocked at most builders’ merchants, and because landscapers build them all the time, getting a quote is easy. Timber also suits a cottage or country garden, and a sleeper laid flat at the right height makes a handy bench.
Sleepers stood on end in a trench can follow a curve, so a timber wall doesn’t have to be straight. It takes more digging and more sleepers than a horizontal wall, though.
Softwood against damp soil rots over time, even when it’s pressure treated, and it needs re-treating every few years to reach 15 to 20 years. Oak lasts far longer but costs a lot more, and new oak can leach tannin stains onto paving. One of our recent customers had a wooden retaining wall from another supplier start to rot after about 10 years, and is now replacing it with Corten.
At 100mm to 200mm thick, a sleeper wall also takes a strip out of every terrace. On a small, steep plot with two or three walls, that adds up to a noticeable amount of lost ground.
How to Build a Sleeper Retaining Wall
Most garden sleeper walls are built horizontally, stacked like bricks and held by posts on the soil side. For a low wall of two or three sleepers, the usual method is:
- Mark out the line of the wall. Dig a shallow trench and lay a compacted gravel base, so the bottom sleeper sits just below ground level.
- Dig post holes along the soil side, usually no more than about 1m apart. Posts are normally buried to at least a third of their length, and deeper for taller walls.
- Concrete the posts in and check each one is upright with a spirit level. Leave the concrete to set before going any further.
- Lay the first sleeper on the gravel and level it. Stack the rest on top, staggering the joints as you would with brickwork.
- Fix each sleeper to the posts with long timber screws.
- Line the back of the wall with a permeable membrane, add gravel behind it and backfill with soil.
For a vertical wall, the sleepers are set straight into a concrete-filled trench, so there are no separate posts.
Steel Retaining Walls: Pros and Cons
Our steel retaining walls are 3mm panels that bolt together, with straight, curved and corner sections. Most customers go for Corten, which weathers to a warm orange-brown over six to nine months. If you’d rather not have the rust, there’s a powder-coated mild steel version in solid colours. Galvanised steel is also available on request.
A 3mm wall takes almost nothing out of the terrace in front of it, which matters most in small gardens. There’s no timber to rot or re-treat, and the curved sections make sweeping terraces and round beds easy to set out. The panels bolt together quickly, and the base has holes for fixing down.
Corten forms a protective rust layer that slows further corrosion. It weathers best where it can dry out between showers, but a retaining wall always has damp soil against its back face. Adding gravel and a membrane behind the wall stops that face sitting in wet soil. With them in place, the wall should last for decades. Every panel comes with a 5-year warranty, and our post on Corten steel lifespan explains how the steel weathers.
Height is the main limit on standard panels, which go up to 700mm. We can make taller panels to order, or for a bigger drop you can build two lower walls stepped back from each other, which also leaves a planting shelf between them.
Steel also costs more up front. While the rust layer is forming, rain can wash orange run-off onto paving below, and our guide on preventing Corten staining explains how to avoid it. The top edge is a folded 50mm lip, which looks neat but is too narrow to sit on.
Sleepers or Steel: Which Retaining Wall Should You Choose?
Pick sleepers if budget is tight or the wall is a stopgap. They suit a rustic garden, and they’re the only one of the two you can sit on. For a wall over 700mm in one run, sleepers are the simpler option too, as taller steel panels are made to order.
Steel is worth the extra when you want a wall to last with very little upkeep, or when a small garden can’t spare the width. It’s the easier way to build curves, and a safer choice next to vegetable beds, where you’d want to avoid old creosote-treated timber.
Plenty of gardens use both. Oak sleepers make good seating around a fire pit, while steel handles the long retaining runs where a slim wall saves space.
Drainage, Height and Planning
Water is the most common reason a retaining wall fails. Wet soil is heavy, and the pressure builds at the base of the wall.
Behind any wall, lay gravel with a permeable membrane between it and the soil, so water drains away without washing soil through. On clay or very wet ground, add a perforated pipe along the base.
A low wall holding back a small change in level is a reasonable DIY job. For anything retaining more than about a metre, or close to a house, path or boundary, get a structural engineer to check it first. Checkatrade puts that assessment at roughly £269.
FAQs
How long does a sleeper retaining wall last?
Treated softwood usually lasts 15 to 20 years, and oak can last 40 years or more. Softwood rated for ground contact lasts longest when the bottom sleeper sits on gravel rather than bare soil and the wall has drainage behind it.
Is steel cheaper than sleepers over time?
Not at the start. In our 5m example, the steel panels cost about twice as much as the sleeper materials. Over 30 years or so, if a softwood wall has to be rebuilt once, the totals get much closer, and steel saves on re-treating in between.
Does Corten steel rust through?
Not in normal garden conditions, as long as it isn’t left sitting in standing water. Salt spray on the coast speeds up corrosion, so it’s less suited to seafront gardens.
Do sleeper retaining walls need posts?
A horizontal wall does. The posts stop the soil pushing the sleepers forward, and timber or steel posts both work. A vertical wall doesn’t, because the sleepers are set into the ground.
How high can a sleeper retaining wall go?
Most DIY sleeper walls stay under about 1m. Above that, or anywhere near a building or boundary, the wall needs to be designed properly, usually with deeper posts and an engineer’s input.