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Yellow Staining on Upstairs Chimney Breast

Postby schnoo10 » Tue Jun 10, 2008 1:19 pm


I have just plastered and painted our upstairs bedroom and there now appears to be a 1ft square yellow stain showing through at the top right hand corner of the chimney breast. The chimney has been blocked off and capped. I have checked in the loft and there is no sign of water penetration so am I right in thinking this is something to do with hygroscopic salts?? and this is more than likely due to poor ventilation?

If my assumptions are correct which is the best course of action?? Airbricks to ventilate? also how do you solve the stain problem??

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Simply Build It

Postby goose » Wed Jun 11, 2008 8:58 pm

Ideally an unused chimney should have ventilation to help prevent damp.
Do you know if the chimney was sweep before been sealed??

Please correct me if I'm wrong - could the yellow stain be caused by old soot in the chimney 'seeping' through if getting damp due to condensation.

I've heard that you can cover stains by painting the area with gloss paint? But the cause of the staining should be dealt with.
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Postby schnoo10 » Mon Jun 16, 2008 12:51 pm

I've heard that about gloss.

The chimney must have been bricked up a long time ago, when we bought the house last year it hadnt been decorated since the 70's!

Anyone else got any ideas before I get glossing?
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Postby htg engineer » Mon Jun 16, 2008 1:52 pm

Any tanks or pipework in loft ?
Yellow staining is normally water marks.

Damp normallly has white marks because of the salts or dark sometimes and mouldy.

Check for leaks around flashing, ridge tiles etc.

Hope this helps
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