An unpleasant surprise

This house just keeps coming up with surprises. The electricians found this one when they pulled up some floorboards. It’s a rather wet wall - on the inside of the second bedroom.

I had noticed that the overflow pipe for the water tank in the loft was dripping on to the wall above the front porch. You can see a line of moss, so it’s been like that for quite some time. I figured, as we were replacing the tank anyway, the problem would then disappear.

What I hadn’t counted on was that some water had also run down on the inside of the wall, and when it hit a connection between the outer and inner walls - like a joist - it ran along it and soaked the inner wall as well.

To find out how bad the problem was, I pulled off the wallpaper in the corner of the room and found some ominous damp patches. And there’s another one in the corner of the main bedroom, plus a rather damp area above the front door directly beneath the dripping overflow.

I cut off the source of the problem by turning off the mains water supply and draining the tank. But it’s going to take time to dry out the walls, especially now that the heating is off and the weather is cold and damp. Maybe I should hire a dehumidifier. Luckily the plaster isn’t crumbling, so I think it will be OK once it’s dry. I’ll put on an anti-mould treatment before redecorating, then cover it with lining paper. 

I’m almost afraid to take down any more wallpaper. What will I find next?