condensation in chimney stack

[Monkeynuts2]

Hi

I have just notice that i have got the dreaded problem of condensation in my redundant chimney stack .The fire was removed years ago and bricked up and a air block put in,

The condensation is forming on the granite lining and creating damp patches, bleeding through the pointing staining it.

I have remove the air block and i can see the condensation on the inside of the stack on the granite stones.

It seems to be only forming on the sooted stones ?

The stack is on the gable wall which takes most of the bad weather .

Im thinking of puting a weak mix over the sooted stones to absorb the condensation ,which means taking out some granite further up the wall .

As the staining is floor to ceiling following the stack.

Any ideas Tony..

 

[Alastairreid]

Has the redundant chimneyhead got a vented cap on it?

 

[noseall]

using an s.b.r. slurry and render can help to beat the 'bleed'.

 

[karlosmaximos]

as someone else said,check that the chimney is still able to breath through a vented cap.
if the stack has been taken down say to roof level, then put another air brick in near the top, this well help to circulate air through the stack and hopefully alleviate the problem

 

[Monkeynuts2]

Hi
Thanks for the replies.

The chimney stack is still in place with a normal pot .

Using a sbr mix would make it waterproof and as a result would make it impervious which would create more condensation ? Unless you mean do a two coat render with the second coat say 5 or 6 to one

Tony

 

[swbjackson]

When you say normal pot do you mean one open at the top? It could be water ingress rather than condensation.

Mike

 

[Monkeynuts2]

Thanks Mike for the reply

The pot is open at the top .

I`ll cap the pot and see if it helps

Thanks Tony

 

[swbjackson]

Make sure you use a vented cap or you will get condensation.

Mike