Just finished a bathroom refit for a relative but have noticed a small damp patch that keeps re-appearing on the bare plaster half way up the window reveal where it meets the window.It starts at the window frame and spreads out over an area about 4 x 2" square. As part of the refit I hacked off the plaster back to brick in the whole room and re-plastered . The wall concerned is a brick cavity wall. Window is upvc.
The damp patch appears after rain and I noticed that whoever fitted the window had sealed the gap outside between window and brickwork with silicone sealant which was fair enough but the gap was about 3/8" inch wide so asking a bit much. I took the silcone out and filled the gap with expanding foam then fitted a piece of cloaking profile over the gap and sealed all round the edge with silicone sealant. I also spent half a day repointing the brickwork outside over quite a large area as it was pretty bad in this general area. It was a decent job and I felt confident the damp patch would not re-appear.
But it has.
I'm now thinking back to the plastering stage and I remember that the brickwork around the window at the point where the damp patch is was in a poor state and I gobbed some bonding plaster in first which probably bridged the gap between the inner and outer wall over a small area but from memory over roughly the same area where the damp patch keeps appearing.
I suspect i've answered my own question but I'll ask it anyway:
Have I made a basic error in bridging the cavity with plaster?
And would that in itself be enough to allow the ingress of damp even though the area outside was weatherproof?
Thanks
The damp patch appears after rain and I noticed that whoever fitted the window had sealed the gap outside between window and brickwork with silicone sealant which was fair enough but the gap was about 3/8" inch wide so asking a bit much. I took the silcone out and filled the gap with expanding foam then fitted a piece of cloaking profile over the gap and sealed all round the edge with silicone sealant. I also spent half a day repointing the brickwork outside over quite a large area as it was pretty bad in this general area. It was a decent job and I felt confident the damp patch would not re-appear.
But it has.
I'm now thinking back to the plastering stage and I remember that the brickwork around the window at the point where the damp patch is was in a poor state and I gobbed some bonding plaster in first which probably bridged the gap between the inner and outer wall over a small area but from memory over roughly the same area where the damp patch keeps appearing.
I suspect i've answered my own question but I'll ask it anyway:
Have I made a basic error in bridging the cavity with plaster?
And would that in itself be enough to allow the ingress of damp even though the area outside was weatherproof?
Thanks