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Condensation around Chimney Stack

Postby DIYDavid » Mon Feb 16, 2009 1:39 pm

I've been reading these forums trying to find a solution to my problem.

I have just bought a Victorian property which has two chimney stacks. The rear stack has been completely dismantled and ends just beneath the roof in the loft space. Around the top of this stack, in the bedroom just below the loft, damp is appearing. There are no leaks in the roof, no pipes near by and on my surveyors report he mentioned condensation in this area. He recommended adding vents to the two unused fireplaces (in the bedroom and the dining room) and also ventilation at the top of the bedroom.

I was wondering whether anyone new if I could some how ventilate from outside rather than put these vents on the inside of the house? This chimney is on a gable end.

Do I just put an airbrick in at the bottom and top? Am I trying to ventilate the stack? Or the Flues?

--Edit ---

Thought I'd add exactly what my surveyor said ...

Additionally condensation was found to be occurring at the top of that chimney/within the roof void and recommend improvement by provision of ventilation grills at high level within the rear bedroom and to each former fire opening in turn.

--End Edit ---

Sorry if my terminology is incorrect. And thanks in advance.
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Simply Build It

Postby stoneyboy » Mon Feb 16, 2009 7:18 pm

I would think that ventilating rooms into a chimney which terminates in a loft will exacerbate the condensation problems.
Try outside airbricks in the top and internal airbricks in the disused fireplaces. This will provide a minimal level of warmth in the chimney which will aid air movement.
The aim is to ventilate the chimney flue thereby keeping the stack dry.
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Postby rigga » Mon Feb 23, 2009 4:39 pm

In part I agree with what Stoneyboy has recommended apart from putting air bricks in from the internal rooms, my advice would be to put all air bricks from the exterior gable wall. Because, if warm air from the internal rooms enters the chimney stack, as it rises and meets the cold air from the vents at the top of the stack then this is where condensation will form. In my opinion don’t let any warm air into the stack, this can be achieved by venting from the exterior.
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