Is the damp still a problem? Is it seasonal (only in late Autumn/Winter)?
Where is the damp located? What type of property? Age? construction (solid or cavity walls)? Do you have cavity wall insulation? Do you have UPVC windows? Do you have central heating? How is it set up? What are you living habits? How many people live in the house? Do you use a tumble dryer? Do you have extractor fans?
Winter only, after heavy gale/rain you can actually see damp/paint bubbling. House build in 1960. Brick cavity wall. Insulation - see above I'm really not sure. UPVC windows. Yes central heating although the damp is the sid of the house with no radiators. 2 people in the house+1 toddler. No extractor fan anywhere. Tumble dryer lives in the garage. I'm satisfied this isn't condensation.
Thanks this has been playing on my mind for some time and your post has had a dramatic calming effect.
Some random facts/questions/thoughts:
There's a tile window cill inside which actually meets the outer course of bricks. An obvious possible possible bridge point.
At some point in the past someone has applied mortar at the bottom corner of the windwo of the window which also bridges across the cavity and th edamp course around the window, the wondow has been out and that looked damp to me and was certainly transferrign some water onto the inner course. However I'm not sure it could explain the amount of damp we're seeing.
Also there's two points at the top of the wall where new holes have been drilled when a new boiler was put in the loft. As far as I can see they weren't sealed by mortar however the angle of the pipes suggests to me that water would drain out rather than in. I'm still suspicious that water might be coming in there, falling down the inside face of the outer course and then crossing over at the window.
The argument against the window being the sole bridge point is that the spread of the water below the window is wide which (perhaps) suggests water coming in at multiple points or perhaps rising damp. When I say wide I mean there is no sign of damp above the window at all. The window is half way up the house and by the bottom of the ground floor but the damp is almost the width of the house. Would it be expected for water to fan out over such a wide area below the point it's coming in?
Another concern is that I'm not sure if the wall has cavity wall insulation. There was a vast amount of foam under the old cast iron bath which I assumed was to insulate the bath itself but it could equally have seeped in from teh gap between the courses are some point in the past when cavity wall insulation was squirted in. I can see no sign of this on the outside of the wall. If there is cavity wall insulation I'd guess that would be sodden and bridging into the inside wall all over the place.
The pointing is pretty bad. I can't help but wonder if getting a builder to do pointing (including a decent bit of mortar round the 'new' pipes) & sort out the window would sort it, I can't see any other way water could be coming in. Problem is finding a good local builder who wants to do pointing. They don't tent to return calls when the word 'pointing' is mentioned. On the other hand if I got to a specialist pointing firm I doubt they'd do the window.
Everything I wrote in my previous posts is still valid as are the images. But there's some new information regarding the window which I think we can say for certain now is a potential bridge point for two reasons.