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Hi all,
With all the intense rainfall and heavy winds ins Sydney over the past week the timber sleeper retaining wall in my front yard has suddenly started leaning over. A few points
- Wall was built aprox 16 years ago before I purchased so not involved in how it was built (photo with no hedge shows just around time it was built - retaining wall and picket fence installed at same time
- I am concerned the base of some of the green picket fence posts are fairly rotten at ground level (they are in large diameter concrete footings
- I wish to stabilise the wall but not after perfection
Plan:
1 - I plan to remove the 3-4 sections of picket fence panels in the image (able to be unscrewed off the green posts) to access behind the wall to clear any debris and allow the wall to be pulled back (there is currently an air void behind the leaning wall so not completely choked with soil and debris).
2 - I plan to add additional vertical posts either timber or steel (in concrete footings) between the green posts on the exposed side of the retaining wall to provide additional bracing once wall is restored to vertical
3 - I will be aiming to leave the marraya hedge alone and undisturbed as it has taken years to establish
4 - Once the retaining wall is restored to a vertical position I was considering bolting on a very long gal box steel behind the retaining wall to strengthen the join (obvious in the photo) and avoid it bowing out in the future.
Questions:
1 - Is the weight of the timber picket fence too much force on the retaining wall once it is repositioned? Especially since the picket fence adds considerable height to the retaining wall. I could remove the picket fence and simply add a few rows of sleepers to avoid balls etc rolling off etc? It would at least allow for easier pruning of the hedge!
2 - It is unclear if the wall was pushed over due to wind, water run off or a large falling tree branch as I was not present when it occurred but it has been very gradually leaning over the last few years - would it be helpful to create some weep holes in the sleeper wall to allow water pressure from behind the wall to escape and relieve the hydostatic pressure on the retaining wall?
Ps - the large hole in the sleeper retaining wall was to allow for an old privet tree which I removed so will also look at closing the space up as well.
Many thanks for your assistance!
Hi @Ben2065,
Hope the Sydney weather is calming down for you.
Let me tag some of our most experienced contributors to the site in @Nailbag, @Jewelleryrescue and @Dave-1 to kick off the discussion with their thoughts on your plan and your questions.
Jason
Good Morning @Ben2065
I will try and step through your questions 
Tho the answers arnt going to be great for saving the retaining wall.
Plan:
1 - I plan to remove the 3-4 sections of picket fence panels in the image (able to be unscrewed off the green posts) to access behind the wall to clear any debris and allow the wall to be pulled back (there is currently an air void behind the leaning wall so not completely choked with soil and debris).
A1 - Pulling back a retaining wall kind of defeats teh purpose. A retaining wall should not be able to be moved 😕 I suggest removing and starting afresh.
2 - I plan to add additional vertical posts either timber or steel (in concrete footings) between the green posts on the exposed side of the retaining wall to provide additional bracing once wall is restored to vertical
A2 - Additional posts would help always especially with a fence on top. However drainage and the way the fence is put together is a better option.
3 - I will be aiming to leave the marraya hedge alone and undisturbed as it has taken years to establish
A3 - You could try to work around leaving the hedge there while rebuilding the wall. I would suggest a transplant to somewhere out of teh way for a season while you work on the area. It tends to take longer to do then we expect and less chance of the rootball drying out.
4 - Once the retaining wall is restored to a vertical position I was considering bolting on a very long gal box steel behind the retaining wall to strengthen the join (obvious in the photo) and avoid it bowing out in the future.
A4 - The posts are the key, they have to be far enough into the ground as to not want to lean. Or you go with a different style wall depending on what look you are after. The idea of the gal box I would possibly use half way through a retaining walls lifespan to help as long as tthe wall itself hadnt picked up a lean.
Questions:
1b - Is the weight of the timber picket fence too much force on the retaining wall once it is repositioned? Especially since the picket fence adds considerable height to the retaining wall. I could remove the picket fence and simply add a few rows of sleepers to avoid balls etc rolling off etc? It would at least allow for easier pruning of the hedge!
A1b - I don think the weight of teh picket fence would be a concern if the posts are solidly into the ground and fixed. If you have someone constantly wiggling teh fence then its teh same for any fence.
2 - It is unclear if the wall was pushed over due to wind, water run off or a large falling tree branch as I was not present when it occurred but it has been very gradually leaning over the last few years - would it be helpful to create some weep holes in the sleeper wall to allow water pressure from behind the wall to escape and relieve the hydostatic pressure on the retaining wall?
A2b - 16 years for a timber retaining wall is a fair go I would say. The way walls are built today and types of walls that people use are differant. Drainage, ground make up, height allowed, footings or piers all have changed somewhat. The draianage/wheepholes are one way to relieve pressure but as your wall has a large lean on it already I dont think it will help correct it.
Ps - the large hole in the sleeper retaining wall was to allow for an old privet tree which I removed so will also look at closing the space up as well.
A - Privet roots are like the top part of the plant The roots themselves could have started the lean on the retaining wall.
Have a look at my profile/bookmarks for an alternative to a timber retaining wall. I really like Gabion styled walls (cages filled with rocks) These need no footings other then compacted earth, allow water to move through itself and have a long lifespan. There are a range of retaining walls that we use. Maybe dry around your area and see what people have used and note the "lean" if any on the walls. In my area a whole bunch of high side retaining walls (brick) all have that same lean. I have thought like you if the soil was removed would teh wall be able to be stood back to true vertical.. I dont think so as the same think would happen but faster as its already weakened.
Dave
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