I have recently purchased a large stone built semi built in about 1910. In the small bedroom there is a damp patch on the ceiling which is around a small, no longer in use, chimney breast. The roof has been inspected by a contractor who advised that the roof is watertight and patch is caused by hygroscopic salts from the chimney breast. The roof is the original Rosemary clay tiled roof with no underfelt. Can anyone advise how to get rid of this patch once and for all and what type of paint to use on the ceiling please?
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Hygroscopic damp patch
- Thread starter SharonG
- Start date
Geoffrey
Member
- Messages
- 83
- Location
- Oxfordshire
It's probably worth checking that the chimney is capped and that the breast has a vent somewhere.
The only way to eliminate hygroscopic damp is to remove the hygroscopic material, ie replaster the patch. That doesnt imply that I'd be willing to assume it is hygroscopic.
Paint on an interior ceiling? whatever you want. Unless youve got intricate cornice work, then use only distemper.
NT
Paint on an interior ceiling? whatever you want. Unless youve got intricate cornice work, then use only distemper.
NT
Penners
Member
- Messages
- 17,294
- Location
- Suffolk, England
If the damp patch on the ceiling is immediately adjacent to the unused chimney, it's almost inconceivable that the chimney is not in some way to blame.
Your builder says that the roof is OK - has he checked the flashing around the chimney? If he assures you that this is also OK, then I imagine the problem must result from rain going down inside the chimney and soaking through porous brickwork or mortar to the outside surface. As Geoffrey suggests, the solution to this would be to cap the chimney (but ensure that there is still air circulation inside it).
Once you have eliminated the damp, allow the ceiling to dry out. Provided the plaster is still sound, you can then paint the stained patch with Stain Block or Stain Cover paint, before finishing with your choice of ordinary paint.
Your builder says that the roof is OK - has he checked the flashing around the chimney? If he assures you that this is also OK, then I imagine the problem must result from rain going down inside the chimney and soaking through porous brickwork or mortar to the outside surface. As Geoffrey suggests, the solution to this would be to cap the chimney (but ensure that there is still air circulation inside it).
Once you have eliminated the damp, allow the ceiling to dry out. Provided the plaster is still sound, you can then paint the stained patch with Stain Block or Stain Cover paint, before finishing with your choice of ordinary paint.