Timber Retaining Wall – Beam Replacement

The engineering on such a wall may prove difficult. We recently built a 6' retaining wall and a couple of 5' retaining walls. The 6' wall was 32 MPA concrete spray using our pool as the footing, the 5' walls are steel reinforced, core-filled besser blocks with footings 600mm deep and 1000m wide. In both cases, using steel and concrete, the engineering was complex. We rendered both walls. We constructed our walls this way to minimise the foot print (the walls are 200mm thick).

Using something like boulders could prove tricky unless you have a 45 degree angle of repose - this would simplify things but also eat up a lot of your back yard.

My neighbour has just build a shorter retaining wall with besser blocks then added a rock finish afterwards - looks rather nice.

If it was built correctly (designed with seasonal wood movement in mind) it shouldn't need anything done to it. Depending on how you would like it to look you might want to use a sealer on it. As for how long it will last that all depends on what was used to build it. If it was pressure treated construction lumber then I'd estimate 30+ years although the newer pressure treated formulas haven't been around that long so no one knows for sure how long it will last.