Capped and bricked chimney breast damp patches on both floor

[jfk111]

In both my downstairs room and the bedroom above I have damp patches forming increasing and decreasing with weather and temp. Directly behind the wall oustide is the chimney breast running up the wall which is capped at the top with the fire places plasterd over inside. Ive heard this could be due to salts ect from buring fossil fuels and the plaster should be removed, walls treated and then replasterd with non gypsom plaster. Is there any other way or any treatment I can use and then reskim over existing plaster? Many thanks J

 

[Alastairreid]

Is the cap vented? and does the bricked up fire opening have a vent?

 

[jfk111]

There are no vents insed the property and the external stack is removed at the top and bricked. i cant see a vent on the top but there are a few airbrick at first floor level.

 

[Alastairreid]

There should be airflow through the entire length of the vent this would mean airbricks on the chimneyhead and ventilation at the lower level.

You should do this before any remedial works to the chimney breasts.

 

[jfk111]

Ok Ive got to check the flashings on another part of the roof this weekend so will check the top of the chimney whilst the ladders are out. should I add some airbricks outside at the bottom and a vent downstatirs inside?

 

[Alastairreid]

Airbricks outside will suffice.

 

[jfk111]

Nice one il give that a go and treat the walls with anti damp paint before repainting

 

[Alastairreid]

Take care on the roof, good luck.

 

[photogav]

I have the same problem and after a few quotes for repairs to the chimney I found a guy who pin pointed the problem. I have 2 chimney breasts going into 1 chimney. A long time ago the large chimney was shunk and 1 of the flues blocked up. Trouble is no one put in ventilation and there is damp on the blocked up side of the wall. His solution - put vents in top and bottom.

So very soon, when I get around to it I will put an air brick at the top and drill holes into the living room wall and put a vent over the holes. That should be job done I hope.