# Forum Home Renovation Retaining Walls  Retaining wall

## alisonol

I am in the planning stages of building a smallish retaining wall. It will be 4 meters long and 400mm high.
I am planning to use 200 x 75 H4 treated pine sleepers for the whole job.
My questions are :
<DIR>Will this sleeper size be OK (Strong enough)
How deep do I need to dig the hole for the posts?
How many posts do I need? I was thinking 1 at each end and 1 in the middle where the join will be. 
</DIR>

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## silentC

I made mine from 200x50. I reckon 200x75 is more than enough. 
I make the posts twice the height of the wall usually, so for a two sleeper wall, I make the posts 400mm deep. Has worked OK for me, except for the one I got too close to with the bob cat, it's now about about 5mm out of plumb. 
I put one post every 1200mm. For your job, I would put a post at each end, one in the middle at the join, and one in the guts of each sleeper.

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## manoftalent

depending on your soil, you could dig 600mm if its a hard packed type or at least 900mm if its very soft and concrete them in ....100 x 100 mm posts and the sleepers coach bolted with 8" bolts ...one either end and one in the middle is ok ...

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## Terrian

> Will this sleeper size be OK (Strong enough)

  
yep, will be fine, 50mm would be OK as long as there is not going to be too much weight against the wall (parking cars close) but the 75mm will look better IMO    

> How deep do I need to dig the hole for the posts?

  400mm high, make the holes (at least) 400mm deep, set them in concrete (300x300x400 holes)   

> How many posts do I need? I was thinking 1 at each end and 1 in the middle where the join will be.

  That will be fine, a 2.4m sleeper cut into 3 will work fine for the uprights.

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## Dan574

have a look at the pdf I attached it might help

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## Tubby2

I'm in the middle of building my retaining wall.
I'm using 200x75mm for the posts and 200x50x2400 for the wales. I've put the posts every 1200mm. The depth of the holes varies from 600mm to 800mm deep. The smaller holes are where the augur had heaps of trouble in the rock, but as its in rock I doubt they'll move.
I have 2 heights in my wall & 600mm & 800mm. 
I used quickset concrete to put the posts in place mostly I used 2 bags per hole but sometimes I used 3 bags where it was a big hole.
I plan on putting blue board over my so I will just use a nail gun to keep the wales in place until I back fill but if I were not using blueboard I would use 2 bolts per post per wale to stop the wales from cupping.

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