Thanks very much for your detailed advice.
We have had the house a year, of note, approximately 10 months ago the neighbours had an extension installed part of this meant having the chimney stacks removed, though I don't think this is likely to be the cause/contributer. I haven't asked them...
Dear DIYnot,
Hopefully this forum can help, and the advice given will help me and others. I live in an end-terrace 3-storey house in South-West London built in the 1880s. This winter and spring we have had some water ingress (see photographs) into the wall around the stair case.
What is...