Chimney damp mystery

[dishman]

I have a small chimney that is now defunct. It used to serve the original Arger back in the 1930s.

To keep costs down (prior to me moving in) the chimney was removed at kitchen level to give more space but retained at first floor and above. The chimney was also sealed at the top and bottom. No ventilation slats visible.

This was all done before I moved in.

Ever since I can remember I have had a small damp patch (which never grows or gets mouldy) in the bedroom onthe other side of the wall where the chimney runs against. The chimney runs internally within the house and not against an outside wall.

My thought is that the capping top and bottom is the cause, somehow, of the damp.

This was recently reinforced by my adjoining neightbour who has had the same work done to the chimney in the distant past. They also have it capped and no ventillation and have the same damp patch in the same place in the same bedroom.

The flashing, although old, looks to be fine.

So, my thought would be to uncap the chimney top and put a pot on it. and drill a hole internally for an air vent and get some ventillation into it?

The only thing I can think of is some odd temperature differential which is causing condensation/damp in a certain spot?

Thoughts?

 

[theprinceofdarkness]

So the steamy air from your bathroom slowly finds its way into the flue and the moisture content then turns into real water which dribbles down and soaks back through the plaster. Needs a bit of ventilation or take the external bit of the flue down and insulate over it in the loft thus making the whole flue come inside the house. I guess it will still have one wall of the flue that is part of an outside wall and thus be cold.
Frank

 

[vinn]

What you describe is typical of an unventilated flue allowing sooty flue chemicals to bleed through to the plaster surface of the chimney breast.
Open up the flue at the old fireplace opening and have it swept and smoke tested is a start.
Examining the chimney stack and flashing and flaunching or capping is next. Plus the stack terminal must be ventilated.
Best practice is to hack off all chimney breast plaster - from all three sides and render back in sand and lime and board finish.
A vent must be fixed at the fire opening if the opening is covered up once again.

 

[dishman]

Again to clarify, as I said in my opening post.

This chimney was removed at ground floor level. It has no vent or opening ground/first floor level nor any any point internally. It is fully capped/sealed externally and internally. The only part that meets the outside is where it protrudes from the roof. It does not form or meet part of any outside wall.

Having said that, your responses seem to confirm my suspicion that it is do do with it being fully sealed.

 

[vinn]

I'm not sure what point you are making?
Nothing I suggested would oppose or misunderstand the details in your opening post?
Where exactly do you find contradictions in my reply?

 

[dishman]

Not your post vinn - there seemed to be some misunderstanding with the reply from prince of darkness.

All replies very much appreciated however.