Rebuilding the 'wall of death'

[Cyclonicity]

After purchasing my house and cutting back the vegetation at the back I was greeted by a couple of retaining walls with a significant lean and very poor structure - one 1.2m high and one (only 30cm infront/below) 0.6m high (7.5m wide). This is a retaining wall holding the garden of the house behind (somehow). It appears to have no drainage, no aggregate behind (purely), and appears to be bedded on soil.

I've attached photos. I'm very new to this so was wondering if you could help.

The low (brick) wall extends to the other properties, leaning in 1 neighbours' garden.

My plan is to take down both walls and rebuild, potentially using gabions as a low-cost option, done properly with proper foundations, drainage pipe behind, gravel behind for drainage etc.

The questions I have are as follows...

- How would we keep the earth behind at bay to avoid the garden behind (neighbours' at back) collapsing in a soily heap?
- Would it be better to terrace with 2 walls (adequate space apart) or is it OK with just 1 wall (this would be preferable in terms of space in the small garden).
- The garden is raised from ground level to get the terraced garden effect (next doors' is much lower down) - if rebuilding the wall, is it OK to build off the level it's on, or would we need to strip back the entire garden to check the foundations??
- This being said, would it be necessary to get a structural engineer in?

Any advice would be greatly appreciated.

Thank you!

 

[Alastairreid]

google gabion baskets.

 

[^woody^]

A 215mm wall with bed reinforced, or a 330mm wall for 2/3 the height then reduced to 215mm. On a 600 wide foundation down to good ground or at least 500 deep. It may be best to design in some returns at each end of the wall which will greatly help with stability.

You tend to find that the ground stays put when you remove the wall and square the loose stuff off.