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Retaining Wall Advice

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  1. #1
    Apprentice (new member)
    Join Date
    Feb 2020

    Default Retaining Wall Advice

    Hi all,

    I am in the market for constructing a new retaining wall. I am considering the following 3 options.
    1. Pine Sleepers + Pine Uprights
    2. Pine Sleepers + Steel Uprights
    3. Concrete Sleepers + Steel Uprights

    I have 6m of wall @ 0.4m high and 28 metres of wall @ 0.6m high.

    Based on that, the 3 options would cost
    Option 1 - Approx $900 of pine for the sleepers + uprights
    Option 2 - Approx $700 of pine sleepers + $950 of steel uprights
    Option 3 - Approx $1050 of concrete sleepers + $950 of steel uprights

    I understand that the concrete sleepers will last longer, however they are 70kg each, compared to the pine being a lot lighter and the pine will possibly warp and shrink.

    Looking for any guidance, recommendations or stories from your experience.


  2. #2
    Seasoned DIY droog's Avatar
    Join Date
    Sep 2005


    How long until you will no longer be responsible for it, and how easy would replacement be in the future ?

    Option 3 is the way for a long term maintenance free structure.
    Option 2 is a good compromise if replacement of the sleepers is easy enough further down the track, particularly at only 2 or 3 high.

    Option 1 I would avoid if you intend to live with the structure, if going this option put uprights every 1200mm.

  3. #3
    Golden Member
    Join Date
    Oct 2017
    Melbourne - Yarra Ranges


    As Droog said.
    Definitely option 3 would be my preferred method. Wouldn't ever consider option 1.
    either way, make sure you put builders black plastic behind them, the stuff you put under concrete slabs. If you go down the pine route, they will last longer and either option 2 & 3 stops any soil constantly leaching through.

    Dont skimp on the depth of hole particularly for the 600mm high. Hole should be 600 to 800 (depending on your soil and the H beam 1000 to 1200mm long (600 in the ground and 600 out). Dont forget any drainage requirements.

  4. #4
    Community Moderator
    Join Date
    Dec 2008


    25 yrs ago I built a timber wall about 20m long ranging in height from nothing to 1.1m from treated pine.

    In addition the posts came up and has a 1.5M fence on top.

    I used this recommendation which I see now has been updated.

    The wall and fence are still there and I have not done nor look like having to do any maintenance.


  5. #5
    Community Moderator phild01's Avatar
    Join Date
    Aug 2009
    Sydney, north


    Quote Originally Posted by Bart1080 View Post
    As Droog said.

    either way, make sure you put builders black plastic behind them, the stuff you put under concrete slabs.
    I would rather omit plastic against pine sleepers and have draining sand there instead. The plastic will hold moisture within the sleeper.

  6. #6
    Golden Member
    Join Date
    Oct 2017
    Melbourne - Yarra Ranges


    Thanks Phil, but disagree. The walls I built 20 years ago, digging around them and pulling the plastic back reveals the sleepers are bone dry and as good as the day they were installed.

    Just on Bros's feedback, my preference on Steel uprights is more around if you need to do need to perform any sleeper maintenance its the one critical piece you dont have to worry about. It also in my view much more ascetically pleasing....each to their own though

    I've known pine sleepers to fail within 10 years - there are too many unknown variables that could have caused this such as:

    • The level of treatment applied to the sleepers. Some treatments are only recommended for above ground use. You need minimum H4 treated pine sleepers (most appear to be H4 CCA) - see table in link https://www.atpine.com.au/treated-pine-timber-guide/ or good hardwood sleepers (hard to get these days)
    • how wet the constant soil conditions were
    • lack of additional permanent protection for where the soil is against the sleepers
    • white ants or borers https://bpic.com.au/do-termites-eat-treated-timber/
    • Uprights holding the sleepers - poor construction methods
    • poor drainage installed - affects any of the options. If using gal posts, having them constantly wet will cause rust which is another reason I use builders plastic as a barrier in addition to good drainage (scorier, slotted pipe and geotextile on top before dirt backfill.

    Poorly made concrete sleepers can also fail with concrete cancer.

    The last big retaining wall I built 2 years ago - 40 meters ranging from 400 to 1400mm high across flat and incline terrain, ~80 sleepers was all out of steel and concrete. I know its personal preference & $, but for me steel uprights is the only option I'd ever consider. I'd be happy to use either wood or concrete sleepers. I chose concrete sleepers with the latest wall for 3 reasons - zero maintenance, high termite and bushfire area. Yes the concrete sleepers are heavy and you will need a second person to assist but after you have your first row down and level its simply a matter of stacking the rest on top within the H beams (wood or concrete options). Have the finished height of the sleeper 5 to 10mm above the height of the steel upright.

    The small one I'd done before Christmas for a neighbor 10m x 400mm high was out of treated pine and the cheaper steel uprights concreted in - worked a treat and fitted well within her budget.

    Another option to consider is redgum sleepers although harder and more expensive to get. I'd done a 10m feature retaining wall in redgum which was belt sanded and 3 coats of marine varnish. It wasn't in the sun which assisted in lasting for 5 years before it needed a maintenance single re-coat. Looked fantastic but would unlikely ever do a polished wall again

    Anyway some good feedback from those above for you to consider your final direction.

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