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Damp gable wall

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22 Nov 2025
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Could anyone please advise what is causing this damp patch please? Chimney was repointed, flaunching checked and flashing repaired a few years ago. Pepperpot cowls were fitted this summer. Chimney has not been used in a decade. It dries in good weather but the recent heavy rains have resulted in this. Attic room condensation has been brought under control recently with venting and dehumidifying as black mould developed on an upper part of the chimney breast wall.
 

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Could anyone please advise what is causing this damp patch please? Chimney was repointed, flaunching checked and flashing repaired a few years ago. Pepperpot cowls were fitted this summer. Chimney has not been used in a decade. It dries in good weather but the recent heavy rains have resulted in this. Attic room condensation has been brought under control recently with venting and dehumidifying as black mould developed on an upper part of the chimney breast wall.

Cavity wall insulation?
 
Do you mean is there or that it may potentially be the cause? Property is over 100 years old. Attic conversion left the chimney breast bricks exposed with gable wall boarded across.
 

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Damp by a chimney is commonly related to the chimney or flue.

Check the verge tiles, the flashing, the stack pointing and flaunching (cement mix around the pots) and the pots.

The spread of that stain would imply damp coming down centrally from the stack or the roof apex
 
Are the elephant foot cowls (pepperpot) sealed to the pots?

But it does appear to be a flashing issue maybe no saddle where the ridge meets stack.
A photo from the front and back might help
 
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