How to build an easy retaining wall using timber?

rozdalley

I am going to cut this bottom half in and use the excess dirt to fill the top half and retain the middle without steps. The area to retain is aprox 620cm wide x 30cm high. Project needs to be fairy easy. Soil is clay. Making level space for a trampoline.

MitchellMc

Welcome to the Bunnings Workshop community @rozdalley. It's terrific to have you join us, and many thanks for your question about levelling an area.

It is certainly possible to build a simple timber retaining wall, and that size is very manageable for a DIY project. The easiest method is to use treated pine sleepers with vertical posts set into the ground behind them. For a small wall like this, you would place H4 treated pine posts at roughly one metre spacing and set them in concrete. Once the posts are in, you can screw the sleepers to the front of the posts, backfill lightly with gravel or coarse material for drainage, and then bring your soil back up behind it. At thirty centimetres high, you do not need complicated drainage systems, but you still want water to move freely through the soil rather than pressing against the wall.

That said, the amount of soil you need to shift to level the full six metres might be more work than necessary, especially for a trampoline area. I had a very similar situation in my own yard, and rather than removing and relocating that much material, I simply cut small trenches for the trampoline legs on the high side. The legs sat neatly down into the ground until the frame was level, and the trampoline was perfectly stable. It avoided the labour of digging out the whole area and building a full retaining wall, and the result worked just as well for everyday use.

If your aim is only to make the trampoline sit level and safe, cutting in for the legs is by far the quickest and easiest approach. If you do want the space level for other reasons, the small sleeper wall described earlier will work well, but it is worth considering how much effort you want to put into moving all that clay before you commit to the larger project.

Here's a helpful guide: How to build a retaining wall.

Please let me know if you have any questions.

Mitchell