Hello I've come looking for advice to see what tradesmen I should get out to have a look at this for me. Or perhaps not worry about it at all. The patches only occur in 2 places and I have only seen them once since I moved into the property back in August 2019 and that was after a very heavy downpour over a few days about 2 months ago. It took about a week or so to dry out and I've not seen them since even with some rain but figured I should get it looked into. This wall is on the outside wall of a 2 story extension built in 2003 on a semi-detached with a cavity. I cannot see anything of concern visually on the outside wall myself. No obvious cracks or anything. There is also no sign of damp in the upstairs room above the garage on the same wall. Thanks in advance.