DIY Doctor UK DIY Forums

I have a split level property showing internal damp due to negative hydrostatic pressure on the lower level where the earth retaining back wall meets the outside wall.
I need some advice on the height of tanking I will need to sort the problem.
With all the rain we've had, I don't expect what damp is showing to get any worse, so if I hack off the plaster 6inches above the highest point and tank it, will the water be able to redirect itself over the top of the repair?
I plan to tie the wall tanking in to the floor by chasing out an inch square gully and filling it with hydraulic cement on top of the bitumen latex emulsion/slurry which will go on the wall before replastering.
Any advice gratefully received.

Water running down a hill can build up as a dam and flow over or round.
You need to deal with this problem from each side of your home, by digging away any obstruction until the water runs out.
Once the water has an escape route, in time possibly months, the problem will disappear.

Thank you for that.
Of the 2 walls, the damp only shows along the length of the outside wall where it retains earth, after which it is dry.
I can't get at either wall from the outside without excavating.
After tanking, could the water be diverted downwards back into the earth or does this depend on the type of foundation? I'mnot sure what my house stands on - its late 70's?