I need to replace a rotted beam in a wood retaining wall (bottom beam in picture). Is it possible to simply slide a replacement beam in place? Also, what about inserting a plastic lining (to the extent possible) to further protect.

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  • Sure. All you need is time and effort. Did you have a more specific question? Cost depends on what we're talking about (and is generally off-topic). Are those 4x6s? Something under $25 if that's the case, but we have no idea where you are. If not, post actual dimensions.
    – isherwood
    May 15, 2019 at 20:01

1 Answer 1


It might not be that simple. Many wood retaining walls use nails or rebar to lock each tier with the one below. You will likely have to remove them from the top-down, but you probably need to anyway. If that one is rotten all the way to the exterior, the others are likely almost as rotten.

I recommend taking it apart completely, removing what needs replaced, and staining/sealing everything (new repairs and old beams) with a good exterior sealant, and building it back up.

  • Thanks. Many of the beams have already been replaced very recently and are in great shape, so a complete tear-down is certainly not preferred. The bottom beam in question does not appear to have securing spikes/bolts as others do. I'm guessing I could utilize a well-positioned bottle jack to lift the upper beams ever slightly to slip in the new beam.
    – David L
    May 15, 2019 at 21:47

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