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Chimney salt stain - require fixing?

Discussion in 'General DIY' started by Lab, 25 Sep 2021.

  1. Lab

    Lab

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    Aside from being unsightly, are these patches a problem? We plan to build fitted wardrobes either side of the alcoves and then a false wall in front of the chimney breast to make it all flush, so these stains wouldn’t be seen.

    Based on the placement, it looks like moisture is being drawn where the dot and dab has been applied.

    Is this something that needs to be fixed? If so, would removing the plasterboard, letting everything dry out and then just then just re-plastering do? Or would a membrane of some sort be required?

    Also unsure if I’d need a plaster or should call in a damp expert.

    Extra into:
    • 1880 Victorian semi.
    • This is an internal wall/chimney breast - staining is only on the chimney stack, walls either side fine.
    • The stack was repointed last summer.
    • Monitored for the last year, the staining gets worse in high humidity and will fade in dry spells
    • No other signs of damp - the room humidity fluctuates with the weather (have a thermometer)
    Note, this is my first post, I’m a total novice, any all all advice and guidance welcome. Thanks!
     

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  3. JohnD

    JohnD

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    they aren't salt stains, they're damp marks.

    Have a look in the loft to see what other damp is visible

    get the source of water repaired. To me it looks wet enough to be rain penetration. Might be pot, flaunching, or flashing.

    and ventilate the flues top and bottom to evaporate away the damp already present.

    As they are at one side rather than the middle, it might be the downstairs flue (passing to the side of the chimneybreast) that has the problem.
     
  4. Lab

    Lab

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    Thanks for the reply.

    It is across the entire breast, I just did didn’t take a full pic, although its worse on the side in this pic, the flue below passes on the opposites side.

    The stack was in a fairly bad state before we had it re-pointed/new lead flashing adding, so I’ve no doubt water was getting in last year.
    With the lack of ventilation, could this be trapped moisture still after a year?

    Either way, will check the attic again, specifically on the side it’s worse and look into proper adding ventilation, thanks.
     
  5. tell80

    tell80

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    Have you had a look at the chimney breast in any rooms below and on first floor?redundant flues are sometimes left unswept and sometimes unvented
    Moisture in a unventilated and unswept flue will mix with the soot and pentrate the bricks and mortar as a chemical solution. on the surface it will attract moisture. the mix of moisture and chemicals will cross the dot and dab cavity through the adhesive clumps and show like it does in your pic.
    For a good job i would remove all plaster board and plaster on the chimney breast.take it back to brick and then use render not plaaster. vent all flues at fireplace and chimney stack flue terminals.
    pics of the chimney stack might help.
     
  6. foxhole

    foxhole

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    Has chimney been capped and is it vented, if not rain simply travels down and causes damp . Definitely don’t waste money on a damp company.
     
    Last edited: 26 Sep 2021
  7. JohnD

    JohnD

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    Where I have seen stains where water came through a sooty chimney, the stain has been yellow or brown from the tarry soot.

    Some chimneys have never been used for an actual fire, and their stains are clear water.
     
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