Finding old chimney flue

27 Aug 2011
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United Kingdom
How do I find the void of an old chimney flue

I have a bit of a damp problem in the chimney inside the house. I've had a few people to look at the actual Chimney outside and no one can find any leaks. One guy actually came up with a plausible opinion which I'd like to investigate.

The house was originally 2 properties with 2 fireplaces. When it was renovated some time in the past they blocked one off. Now it appears there is damp in the wall where the old chimney was and in the section that leads upstairs. The guy who came to see it says it could be the old disused chimney flue has condensation inside.

He suggested taking a brick out in the attic at the top and drilling holes and covering with a vent in the bottom to flush the void with fresh air. All well and good, but the flu isn't a straight up and down, it goes on a diagonal, so how do I find the void? The damp patch gives some indication, but it's bigger than a flue. Is there a technical or instrument that will do that or is it a case of trail and error?


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