Short term damp fix

9 Dec 2011
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United Kingdom
I have a damp problem which I've been advised is due to salts from a chimney coming through a wall and causing the surface to be hygroscopic so damp air condenses on it. I've had window repairs so hopefully have reduced the level of damp air getting in. The advice I was given was to have all the plaster hacked off and the wall redone with various products to keep the salts at bay.

The cost and disruption has made me look for an alternative. The existing plaster is in good condition, so I wonder if I can scrape off the existing paint and some apply some appropriate material to the plaster. What would work (if anything).

One other issue is that some of the paint has a bluish tinge. It went on grey but it seems that the pigments have separated on the damp areas and blue has risen to the surface. Is this normal?
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Try Zinsser BIN as a paint sealant - it works brilliantly with what it's designed to do - but please be aware that if the chimney has water ingress problems then these will eventually need to be addressed.
John :)
Why not post a photo of the c/breast?

What you mean by a "short term fix" - I dont know? You have a long term problem, and no sealing with anything "brilliant" or not will work.
Any paint or sealant will be blown off by the liquidised chemicals coming through the chimney breast brickwork.

The thing to do is to have the flue or flues in the c/breast swept.
The flue must be vented top & bottom, and the stack examined for water tightness.
All plaster on the c/breast surface must be taken back to brickwork & then rendered with a 3:1 sand and lime mix.
None of the above works are expensive.

Is the flue in active use - does it have an appliance in place?
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This is short term because right now I can't face the expense or the mess. I've been quoted £4500 for the job, that's before decorating and cleaning up. Eventually I have to bite the bullet I know. The chimney I'm referring to is in the house next door and goes up 3 floors. It's not in use at present but is at least 200 years old. The flashing and pointing at the top of the chimney have all been repaired and it vents freely AFAIK. However I think I may offer to have it swept. After that I'm tempted to try the Zinser BIN.

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