Hi,
I recently built a house and have leftover topsoil which I plan to use some of it to build a retaining wall/garden bed and also backfill the yard.
For the retaining wall, I’m planning to put it against the colorbond rear boundary fencing but unsure how far to extend it out. It’ll be 600mm high to meet regulations. I am planning to use concrete sleepers with the posts held in place with concrete. I'll add Ag drainage behind the retaining wall also and connect it to the stormwater drain.
I’m unsure what to put in front of the colorbond fencing to prevent damage/rust to it and was looking for some recommendations/advice. I was planning to put some plants in the retaining wall.
And also, I plan to backfill the yard to level it. How high should I level it to the hardscape? I plan to lay turf down when it gets warmer.

