Special Plaster for damp chimney?

8 Jul 2008
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United Kingdom
So, we have an decomissioned chimney. It is already removed and ground level but still exists on first floor, loft and on the roof. When this was done it was fully capped and sealed internally and outside (concrete slab on top).

However, there has always been a patch of damp on a bedroom wall on the other side of the chimney breast. The damp patch is at the the part where the wall joints with the ceiling. To me this suggests an area where the chimney cools as it enters the loft space (condensation). The chimney itself runs internally through the house. It does not come into contact with an outside wall.

My initial thought is that there is not enough ventillation. So it needs the concrete slab removing and a ventilated pot placing on top as well as a vent internally.

Spoke to a builder about this and he said that the best thing to do was to fully replaster the damp area but to use a special plaster specific to this task.

He seemed doubtful that ventillation would have much effect but will still quote but also suggested this special plaster.

As am having the room re-skimmed it is not a big issue. Just wondered what plaster he may have been talking about.

Personally I do not see how a special plaster will fix the issue. It will just hide the problem will it not?

Thr issue is the damp, the plaster will not stop the damp.
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There have been a number of recent posts on this topic in this forum and the building forum - I've personally answered a few. If you read back you will get quite a bit of useful information. If you then have any further questions then come back.

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