We had an extension built in 2005 and for the last couple of years we've noticed some damp near to the back uPVC door. When I pulled back the vinyl flooring, the first 4 inches or so in feel "damp" to touch and on the new interior wall (just above the skirting board (this was the old exterior wall before the extension)), on occasions the plaster looks damp too. I first discovered it as the paint was bubbling so took it off to keep an eye on the problem.
Weâ€™ve tried ourselves to investigate what's going on. At first we thought it was because our patio was laid literally an inch beneath the sill of the new door (well above the damp coarse level) so last year I removed the slabs closest to the door and there are now a good 2 bricks beneath the sill, but still the problem persists (although the damp above the skirting is virtually gone).
I had a look back on the photos we took as the extension was built and noticed that the damp proof material was cut off and the door laid directly on top on the exposed bricks. Could this be the cause of our problem do you think? Should the door have been laid onto the damp proof coarse?
I've also done a bit of detective work and noticed that if I pour some water on the sill inside the door frame at the bottom, whilst the water drains out of the drainage holes to the outside, water is finding its way to the corners of where the door meets the brickwork - there is a small gap that I've been able to put some kitchen roll in which is dry beforehand, but within a few minutes of pouring the water into the sill becomes wet. To me this means water or moisture can then penetrate back into the house and floor.
We're at a loose end and would appreciate your opinion before contacting our builder and / or window supplier.