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rising damp at base of hearth?

Discussion in 'Building' started by jc86, 25 Nov 2014.

  1. jc86

    jc86

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    Hi all,
    recently moved into a new house and tackling the damp!
    We have a chimney stack which has been leaking. Upstairs we had a large damp patch which was caused by leaking felt and rotten batten. So the roof is now sound and upstairs is sorted.
    However, after the recent cold and wet weather, have noticed some damp around the base of the downstairs fireplace. It's well ventilated, and the stack has one older pot which looks fairly open, and one smaller one which looks like it has been replaced. House is 1930.
    Fireplace has had a concrete slabbing to raise it up a bit. Will post a pic ASAP.
    Stack backs on to outside wall which looks fine. No other sections of damp in the downstairs room.
    Any thoughts on cause and remedy appreciated! ?
     
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  3. Burnerman

    Burnerman

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    Historically, hearths were concrete, cast straight on to the earth without any DPC.
    Therefore, there's no reason why damp can't slowly rise. When the house was built, the occupier wouldn't notice things because the fire would automatically keep things dry.
    The solution is to dig the hearth out, apply a DPC such as a Visqueen layer, and cast new concrete on top.
    Or.....fit a wood burner and recommission the chimney :p
    John :)
     
  4. jc86

    jc86

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    Cheers - on reading this I wonder if capping the pot and keeping an eye may help. We could hear water dripping down every ten seconds or so when it rained hard, so is it more likely it's travelling down the stack than up? Only thing is the damp is worse at the bottom and there is no sign of it trickling down the inner stack?

    ..http://www.diydoctor.org.uk/projects/damp-chimney-breast.htm
     
  5. theprinceofdarkness

    theprinceofdarkness

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    That 'orrible stain at the back looks like penetrating damp, as the back of the fire place is likely to be single skinned. The water is soaking down the outer skin and when it reaches the DPC, it builds up and leaks inwards.
    What is the outside of the wall like in this area?
    Frank
     
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  7. jc86

    jc86

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    Thanks for the reply.
    The outside wall looks totally dry above the damp course and is no different to any other wall on the house?
    Going to cap the chimney off this weekend (with vent) as it's basically an open 30cm pot at the top.
     
  8. NeoL

    NeoL

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    Did you resolve the problem? I'm facing a similar one, though the fireplace is removed, damp started raising.
     

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  9. bobasd

    bobasd

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    NeoL,
    you are not "facing a similar one" - far from it.
    do you expect to get better advice from a "dead" four year old thread rather than one from 60 mins ago?

    fwiw: the above thread does not come to a resolution, and it contains inaccurate advice.
     
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  10. NeoL

    NeoL

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    I was wondering how it ended up. Reading various old ones, would be good if after so many years the issue is resolved and what solved it.
     
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