How many sleeper posts do I need?
Two ends, one intermediate per joint, one corner per turn. Here is how to turn a run length and a wall height into an actual order in about two minutes.
Most people ring up with a length and a height and want to know what that costs. The maths is short enough to do yourself, and doing it first means you order once instead of three times.
Step one: sleepers per course
Sleepers are 2.395m long. Divide your run by 2.4 and round up — the rounding covers the bit that disappears into the channel at each end.
A 10m run is 10 / 2.4 = 4.17, so five sleepers per course.
Step two: posts
Two end posts, whatever the length. Then one intermediate for every joint, which is always one fewer than the number of sleepers in a course.
Five sleepers per course means four joints, so four intermediates plus two ends. Six posts for a 10m wall.
Straight runs
| Run | Sleepers per course | End posts | Intermediate posts |
|---|---|---|---|
| 2.4m | 1 | 2 | 0 |
| 5m | 3 | 2 | 2 |
| 10m | 5 | 2 | 4 |
| 15m | 7 | 2 | 6 |
| 20m | 9 | 2 | 8 |
If the wall turns, swap an end for a corner at each turn. An L-shaped wall down one side of a garden and along the back has two ends and one corner — not four ends.
Step three: courses
Each sleeper laid flat gives you 195mm of height. Five courses is 975mm, six is 1.17m. Multiply the sleepers per course by the number of courses and that is your timber.
Ten metres, six courses high: five sleepers x six courses = 30 sleepers, plus the six posts.
Step four: post height
The post has to cover the wall plus the bit in the ground. Take the finished height, add half again as a starting point, and round up to the nearest available size — 600mm, 900mm, 1M, 1.2M, 1.5M, 1.6M, 1.8M, 2.0M, 2.4M or 3.0M.
A 1.17m wall wants about 1.75m of post, so a 1.8M. That leaves a little steel proud at the top, which you can trim, and a little margin, which you will be glad of.
The six posts for that wall
Send us the length and height and we will check the schedule before you commit. It takes us a minute and it has saved a lot of people a return trip.
Frequently asked questions
- How many sleepers do I need for a 10m wall?
Five per course. At six courses — about 1.17m high — that is 30 sleepers, plus two end posts and four intermediates.
- What height sleeper post for a 1m wall?
A 1.5M or 1.6M post is the usual answer: roughly a third goes in the ground, leaving about a metre standing, which is five courses of sleeper.
- Do I need a post between every sleeper?
At every joint, yes — that is what an intermediate post is for. Sleepers are not designed to span past a post or to be joined between them.