Damp patch on chimney breast

[simonroe]

We have a mid 18th century house with a modern extension. When we purchased the property earlier in the year our surveyor recommended we had the chimney lined. The chimney is in the lounge and has a multi-fuel stove. We've had a flexible stainless steel liner installed. We've also stripped back the old wallpaper and redecorated. Recently we've noted a damp patch appears on the chimney breast wall above the fireplace after heavy rain. This lasts about 3-4 days and then becomes almost unnoticeable. We've checked the flashings which appear ok. The chimney has a wire bird cage on the top. There is no sign of any problems on the chimney breast in the bedroom above the lounge. Any suggestions?

 

[Mr.C]

If a stove is to be fitted into a fireplace then the throat of the fireplace has to be sealed off using a register plate.

The register plate is made from 2.5mm steel and has a hole for the flue pipe, a sweeping trap and support brackets

Is there a rain cowel at the top of the liner?
It sounds as though water is penetrating from ABOVE the flashing, running down the gap between liner and stack and resting on the 'throat' section of the old fireplace; this in turn transmits to the inside where the damp appears.

Suggest; repointing ABOVE the flashing and painting with a waterproof paint (WICKES do a tin), and making sure there is a rain cowel fitted at the top.