Renovating 1920s external wall

[tonDIy]

Hi guys would like some opinions on where to go next. So firstly this is a semi detached room which seems to have both penetrating damp and condensation under the bay window. My question is firstly, should I go back to the brick layer to put in some insulation and drywall. Or once the penetration damp is fixed remove all the affected plaster and just skim the rest?
It also looks to me like someone may of thought it was rising damp previously so they’ve done a treatment on the lower part of the wall? Any help apppreciated it’s a non cavity 1920s red brick wall, from my understanding lime plaster/cement is more for older stone. Below the newer plaster is horse hair plaster which seems pretty crumbly

 

[JohnD]

It would be useful to find out where the water is coming from so the fault can be repaired. Please photograph the outside wall, all the way from the ground to the roof. Indicate the position of the DPC. Check you have plenty of airbricks and they are not blocked. Stand back and take wider pics of the inside walls, preferably in focus, and attach the files, not images of your phone. Take up that floor covering and look under the floorboards.

It is very common for silicone injections to be pointlessly used instead of repairing the fault that is the source of the water. This is futile.

Common faults are:
DPC bridged by earth, render or paving
Broken drain
Spilling gutter
Pipe leak
Sloping ground causing puddles against the house
Gaps round or above windows letting rain in

 

[tonDIy]

Thanks John, I was planning on fixing the damp. The question was more around what to put on the walls after the damps fixed due to current plaster conditions

 

[JohnD]

First things first.

 

[tonDIy]

Given the damp issue is fixed suitably, what approach would you take for external walls in the UK?