I had a boiler installed (first floor) and the external pipe leaked onto the wall outside, making my downstair's neighbour's bedroom wall damp. It was a low level leak but continuous through the thin pipe for a few days before we realised.
The interior wall was damp for days before drying out (though it was July). The neighbour wants to check it doesn't need damp proofing before painting again, especially as it's a Victorian house with old bricks and mortar.
If I ask a damp proofer for advice they'll say yes it does need doing. Would a home surveyor come out and confirm first? Who else can I check with?