Chimney condensation

[Km32]

When i had a loft conversion done a disused flue was capped. This has led to condensation. The brick stack runs down the side of the house. The condensation has resulted in a large damp area 2m x 2m around the bottom half of the stack. Internally i have noticed tarry deposits coming through the plaster

If i put some air bricks at the top of the stack to restore ventilation will this cure the condensation issue. Also will the brickwork dry out in due course (or does this need to be repaired)

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[PrenticeBoyofDerry]

Air vents top and bottom of stack, and a Rain Top Cowl, chimneys should not be capped off.

 

[^woody^]

In addition the the ventilation advice, you will now need to strip off all the plaster and coat the wall with a suitable sealer to stop the tar leeching through

 

[Km32]

Thanks all

Once the ventillation is restablished and the surrounding brickwork dried out (am told could be upto six months - is this right?) will the leeching stop and i can then simply paint over the internal walls?

May also need to repoint.... Is this a good time of year to do it and should i not wait till the brickwork has dried out

 

[PrenticeBoyofDerry]

like woody has mentioned, the tarry stain will be because of leaching, this is caused by the old coal fire and the depoists still left inside the chimney.
When it becomes moist it will penetrate through the stack and in to the plaster.
This will be a difficult stain to mask and the best solution would be to remove the plaster/render from the wall and have done again.
But make sure you have resolved your condensation problem and any damp issues first.
While the weather is freezing, it is not a good time to have it re-pointed as this will effect the curing of the mortar but as soon as the weather starts to creep up above 4 degrees c, then I would recommend having it looked at.
I would also consider having the chimney swept for good measure.

 

[hotrod]

He won't be able to make a wish PBoD .

 

[ianblue]

When i had a loft conversion done a disused flue was capped. This has led to condensation. The brick stack runs down the side of the house. The condensation has resulted in a large damp area 2m x 2m around the bottom half of the stack. Internally i have noticed tarry deposits coming through the plaster

If i put some air bricks at the top of the stack to restore ventilation will this cure the condensation issue. Also will the brickwork dry out in due course (or does this need to be repaired)

[/b]

I would like to know what the position was before the chimney was capped. Was it sealed off at the bottom? Was an air brick or vent fitted at the bottom? Was the top open to the elements?
How can you be sure the dampness is being caused by condensation. Presumably you feel the condensation is being generated within the chimney. The advise you are being given sounds good because whether the damp is being caused by condensation, rain or moisture ingress through faulty brickwork the flow of air should help to remove the dampness. Although if you are leaving the top open with a rain cowl there seems little point in incorporating an air brick on top.
Sufffice to say I have cured a number of damp patches on walls by capping the chimney!