Walk into the yard and ask for "a concrete sleeper" and the first thing we'll ask back is: which one? Every sleeper we sell comes in a length, a height and a thickness, and the thickness is the one that matters most. Here's how the sizes work, so you can read a product page or a quote and know what you're looking at.
How a sleeper size is written
Sizes on our site are written length x height x thickness, in millimetres. A 2000x200x80 sleeper is 2 m long, 200 mm high (the face you see once it's in the wall) and 80 mm thick.
- Length sets your post spacing. A 2000 mm sleeper means posts at 2 m centres, a 2400 mm sleeper means 2.4 m centres.
- Height is 200 mm across the first-grade ranges, so five sleepers stacked make roughly a metre of wall face.
- Thickness is what changes the strength, the weight and the price. That's where the names come in.
Standard, heavy duty and extra heavy duty
Both our first-grade makers, Silvercrete and Outback Sleepers, sort their sleepers into the same three families.
| Family | Thickness | Lengths we list |
|---|---|---|
| Standard | 75–80 mm | 1500 to 2400 mm, depending on the range |
| Heavy duty | 100 mm | 1500 to 3000 mm, depending on the range |
| Extra heavy duty | 120–150 mm | 2000 to 3000 mm, depending on the range |
Not every range comes in every size. Comet, for example, runs from a 2000 mm standard up to a 3000 mm extra heavy duty at 150 mm thick. Lonsdale starts shorter, with 1500 mm and 1800 mm lengths that suit garden beds and steps. Each product page lists the sizes that range comes in, with the price of each, ex GST.
We also list cribs, which are 100x100 mm and come in 2000 and 2400 mm lengths. They're a capping and edging piece, not a wall sleeper.
Why thickness matters
A retaining wall sleeper spans between two posts and holds back the soil behind it. The higher the wall, and the further the span between posts, the more load each sleeper carries. A thicker sleeper carries more.
That's the rule of thumb, not a design. How thick your sleepers need to be depends on the retained height (the height of soil the wall holds back), the soil, the drainage, the post spacing and anything sitting on top of or behind the wall, such as a fence, a driveway or a shed. If your wall needs council approval, the engineer sets the sleeper and post sizes, and you order to their drawings. Our post on council approval for retaining walls in SA sets out when that applies.
For a wall that doesn't need approval, the wall builder on this site gives you an indicative materials list from the wall length and height. It's an estimate of materials, not an engineering design.
Thickness also picks your post
Sleepers slide down between the flanges of the steel posts, so the post has to be wide enough inside to take the sleeper. A sleeper that's too thick for the post won't seat, and that's a problem you want to find on the quote, not on the day.
- Sleepers 75–90 mm thick fit 100UB or 100PFC posts.
- Sleepers 90–110 mm thick, which includes a 100 mm heavy duty, need 120UB or 125PFC posts or larger. They won't seat between 100UB or 100PFC flanges.
There's more on this in our post on matching steel posts to your sleepers.
Weight and handling
A heavier sleeper is a heavier lift. For a sense of scale, a 2.0 m Lonsdale standard sleeper weighs about 74 kg. Heavy duty and extra heavy duty go up from there. That's two people per sleeper on the tools, and a reason to think about where the truck drops them. We can place an order on site, past the kerb, so your crew isn't carrying sleepers up the driveway. On-site placement is priced at the kerbside rate plus 15%, and the Delivery and Freight page has the full table.
Colour and finish come last
Once you know the thickness and length, pick the look. Smooth faces such as Comet (grey) and Lonsdale (grey), leaf faces such as Titan, rock faces such as Asteroid, Nova and McLaren, and woodgrain faces such as Pluto and Ashwood. Colour and finish don't change the size rules above, so sort the size first and the look second.
Still not sure?
Send us the wall length, the retained height and the delivery suburb, and we'll put together a quote with every item priced line by line. Metro quotes come back within 24 hours. Give us a call on 0439 361 734, email sales@fenceplinths.com.au, or come in and have a chat at the yard at Virginia.
Cheers,
Alex and the team