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Painting Over Damp Stain

Discussion in 'Decorating and Painting' started by NLM1990, 9 Sep 2017.

  1. NLM1990

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    I have a damp stain caused by crack on exterior wall which I've sorted out and now im left with the damp looking stain to sort out.

    What do you all recommend I do to tackle this issue in terms of sanding down and what type of paints I need for the job?

    Thanks.
     
  2. Doggit

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    You can either cover it with oil based undercoat, or use a more modern equivalent like this. Then you paint as normal once it's dry.
     
  3. NLM1990

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  4. Doggit

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    Yes, it's solvent based, but as the screwfix can is cheaper, how big is the stain.
     
  5. chappers

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    oil based undercoat is the old way there are better products out there now, the screwfix stuff is OK and can work I have used it plenty of times, it's probably better than the undercoat. If the stain is quite severe/maybe still a bit damp then something like Zinsser BIN, which contains shellac might be needed or even Zinsser Gardz which will cover just about anything
     
  6. NLM1990

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    I've tried the Zinsser BIN in the past and I applied it to the wall when on the bare plaster after I sanded it back and I found that when I then applied two coats of the coloured matt paint which is Dulux 'Timeless' which is a slighly off white and it wouldn't paint over the Zinsser BIN without it showing through.

    Did I do something wrong?
     
  7. chappers

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    how many coats, as it is shellac based it does dry a bit shiny and can take a few coats to stop the sheen showing through.
     
  8. NLM1990

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    I only gave it one coat.

    What about using Zinsser 123 as it sounds like it has similar stuff to the BIN but its water based not oil or am I just better off using an oil based undercoat?
     
  9. NLM1990

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  10. chappers

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    If it is just a stain and completely dried out then 123 would probably sort it. As for your previous attempt one coat of emulsion really isn't enough stain or no stain
     
  11. NLM1990

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    the wall is still a bit damp.

    Am I better off in this case to use an oil based undercoat or the spray you mentioned then a couple of coats of emulsion to sort it out?
     
  12. chappers

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    your best bet would be to let it dry some more, at least until it feels dry on the surface then I would use BIN to be sure
     

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