Hi Scott, thanks for your helpful reply. My home warranty insurance is still valid.

1. The council sent their engineers out for a look today and pretty much said the same as you. There is no problem with the retainer wall: the issue is with the drainage system. I'll look into those atlantis cell drain systems you mentioned. I assume a drainage problem would not be classed as a structural fault and would need to be fixed at my own expense?

2. I think you are right about the crack being superficial and not structural. It looks like the crack is in the render and not the brickwork below.

3. Yes, it's the depth of the concrete steps I'm talking about and not the width. Some of the steps half way down the stairs fit my whole size 13 boot from toe to heel plus a few extra centremetres protruding out the back of my foot, but if I stand on some of the lower steps my heel is hanging over the edge. Where can I view the relevent chapters of the BCA – is it available online? Would this fault be a structural issue?

4. I thought the chipboard would have been screwed or nailed down but the way it's starting to lift looks like it's only held on with the glue! Maybe there are screws in there somewhere. Perhaps they were placed too far apart and the glue is lifting in between? I probably won't know unless I pull the carpet and floating floors up. If there are no screws holding them down I assume this would be a structural issue for the builder to fix?