Confusing damp

[pontsian]

Hiya,

The situation is that in the kitchen, we have had the chimney opened up so a range cooker can fit in. It's perfectly done, however, on the pillar nearest the wall to next door, there is damp. It's about a foot and half up from the floor. The floor of the chimney which is old flag stone on earth is also damp towards that side of the chimney. The builder used plasterboard and dot and dab to make the opening square, because the bricks were very poorly pointed. It's been damp for over a year now, and doesn't seem to get any bigger. The other chimney pillar is dry, as is that portion of the floor. Above the damp patch upstairs is the shower. It's an old solid stone early 1900 end of terrace with no damp proofing. The chimney breast is on the wall between the kitchen and utility room.

I'm wondering, could the pipework to the shower be leaking into the chimney above and running down inside because there's no damp near the ceiling or anywhere else.
Also, during periods of hot and dry weather it can all but disappear. As long as its dry for a week or more. When it rains it doesn't get much worse.
Finally, how long will it take for the plasterboard to disintegrate, because at the moment, its still very sound with no mold growth or effloresence or salt staining. (which I'm surprised, cos if water was dripping down a previously used coal chimney, it would be full of salts or so I would presume).
The chimney is vented top and bottom, and recently (last 3 yrs) repointed.

Sorry for such a long post.

Ralph.

 

[PrenticeBoyofDerry]

what type of cowl do you have on the chimney, is it a rain stopper?

 

[pontsian]

No, its an open type pot. If its rain water, why does it take so long to dry out? Surely that much rain wouldnt come down such a small opening?

 

[joe-90]

It's caused by water vapour in the house condensing inside the chimney. If you have a boiler or gas fire venting up it it will be very noticeable. Take a walk past some old brick semi type houses and you'll see damp all the way up the chimney breast.

 

[pontsian]

Is there anything I can do about this condensation? I know that next door has a downstairs shower, which they have vented into their chimney. Would that have any affect? Should I do anything to stop the damp or just put up with it. (its not horrendous, but will have to be painted or covered somehow).

Thanks for the replies.

 

[thatbloke]

Is the plaster board preventing the wall from breathing? Adding modern materials to older houses can prevent or inhibit their breath ability and cause damp.
Ideally a lime plaster should have been applied rather than cheap and quick plasterboard.

 

[pontsian]

Yes, I suppose that's possible also. I don't think lime render would have been able to produce the nice square chimney opening, since the bricks were so shoddy. Also, when your paying off your first mortgage at extortionate rates, cheap is often the only way to get it done unfortunately. And its hard finding a decent builder who knows what traditional building methods were/are.

 

[joe-90]

JohnD is the condensation expert.