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Damp patches on chimney breast – leak or condensation?

Postby wetrot » Sun Jan 02, 2022 1:23 pm


I’m having a damp/water ingress issue on the old chimney breast wall of my 1890s terraced house. The chimney was removed before we moved in. There is ventilation of the chimney breast upstairs and downstairs.

We started seeing some damp patches on chimney breast wall both upstairs and downstairs a couple of years ago. Had the roof repaired and that back wall re-rendered, and it seemed okay for a while, but the damp patches have returned. We try to open the window in the upstairs room as much as possible but that doesn’t seem to help.

Could this be a condensation issue??

Or is it likely a leak in the roof? The original slates are still on the roof but were relaid a couple of years back so I’m unsure why the issue has returned.

Any suggestions would be very much appreciated.

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Simply Build It

Postby stoneyboy » Tue Jan 04, 2022 12:40 am

Hi wetrot,
The damp either side of the window may be due to a defect in the flashing of the pitched roof just below the window. This may also be the cause of the damp patches downstairs.
Also check your rendering for hairline cracks - they will such in moisture which will then be trapped under the rendering.
Regards S
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