What retaining wall sleeper span?

[kippo]

Hi, Im planning on building a small retaining wall at the front of my property using 75mm by 200mm by 2.4m hardwood sleepers (class 2 hardwood). It will be 1 sleeper high (200mm). The uprights will be made from the same sleepers.

Would it be ok for it to span the full 2.4m length of the sleeper between the uprights or should I place a upright at 1.2m intervals.

Also how deep should the uprights be cemented into the soil (its very sandy soil).

[JacobZ]

Hi @kippo,

You won't have any issues simply putting a post at the end of each 2.4m sleeper as a post and joiner. If you were using 50mm thick pine sleepers as opposed to 75mm hardwood sleepers, I would consider adding a post to the middle of that span, but even they should be fine at only 1 sleeper high, as the weight of soil they are retaining won't be that much.

I would cut my posts to 450mm, have 150mm above grade to attach to the bottom half of the sleeper and then 300mm in the ground concreted in. This will give you a nice, strong hold while allowing you to conceal the posts beneath the soil.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[kippo]

Thanks JacobZ.

[kippo]

@JacobZ Just to confirm can I have the upright behind the sleeper and buried in the soil that the sleeper is retaining. The way I normally see this done is having the upright in the front so the sleeper presses against it. I want to hide the uprights for aesthetic reasons and to make mowing easier.

I plan to attach the sleeper to the upright using two M10 coach bolts at each end so I figure this should still be plenty strong enough.

[JacobZ]

Hi @kippo,

At one sleeper high, you would be fine having the posts behind the sleeper. If the wall were higher, I would be more inclined to have the posts on the outside, but 200mm of dirt is not a huge amount to retain.

With two bolts through each end of the sleeper, it will be plenty strong.

Let me know if you have any further questions.

Jacob