Magnesite and damp concrete floor

Discussion in 'Subfloor Preparation' started by Vienna, Feb 22, 2024.

  1. Vienna

    Vienna Member

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    Hi everyone, just wondered if anyone could help me. I have a 1950's bungalow that had blown magnesite floors when I moved in. Luckily was asbestos free, so removed it all myself. However the concrete base underneath is still very damp almost a year later.

    Bought a damp meter and it has really high readings. The walls aren't damp. What do you think the issue could be? Do you think there wasn't a DPM installed? What is the easiest and cheapest option of covering the concrete base so flooring can be laid? Am I able to to lay a DPM over the existing damp concrete floor? Many thanks for any help.
     
  2. mjfl

    mjfl Well-Known Member

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    If the Magnasite was installed in the 50's > 70's then I would say anything under that is the same age. So I doubt you even have a sheet membrane in that floor at all. It will need digging out and done to regulations.
     
  3. Paul webb

    Paul webb Well-Known Member

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    Possibly get it asphalted
     
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  4. merit

    merit Well-Known Member

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    No dpm. You cab get a liquid dpm put in
     
  5. Vienna

    Vienna Member

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    Thanks for your help everyone. So a liquid dpm over the top is an option? Or do I really need to dig the concrete out and start again? Was hoping to do the work myself, but going to have to get someone in aren't I?

    I did go round my neighbours today (my bungalow is a semi) and her floor readings were fine. But I know they did a lot of work on her floors about 10yearsago, so I'm guessing her issues are resolved.
     
  6. dazlight

    dazlight Super Moderator

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    I’d go with asphalt at 20mm thickness
     
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  7. Rugmunching

    Rugmunching Well-Known Member

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    Asphalt would be the quickest and easiest (less stress) option
     
  8. Vienna

    Vienna Member

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    Brilliant thankyou! Do I need to try and dry the concrete slab out first with dehumidifiers or is this not necessary?
     
  9. tarkett85

    tarkett85 Well-Known Member

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    Asphalt will be your best option but don’t try bonding a solid wood to it


    Sent from my iPhone using Tapatalk
     
  10. Vienna

    Vienna Member

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    So carpet would be best to let it breathe, thanks.
     
  11. dazlight

    dazlight Super Moderator

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    What damp meter do you have ?
    To do it cheap

    Visqueen sheet
    Underlay with moisture barrier
    Laminate
     
  12. merit

    merit Well-Known Member

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    What depth was the magnesite? You could put down a sheet dpm and get a screed poured in if you have enough height
     
  13. merit

    merit Well-Known Member

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    i dont think you ever dry it out. Its probably sitting in wet earth
     
  14. Vienna

    Vienna Member

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    Just a cheapy from Amazon, Brennenstuhl. Worth getting a decent one then?

    I guess I have also worried a little that I may have a leak in the pipework (drain) running down the side of the house. As part of the concrete drive has started to tilt and that's next to the dampest floor in my bedroom. Though speaking to other neighbours on my road, they all say the ground has always been very wet here and people's driveways tend to fail very quickly.
     
  15. Vienna

    Vienna Member

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    The magnasite was 150mm thick. I had a flooring chap out last year who said they could lay a screed down (I think he said self levelling compound, but I would need to let the floors dry out first) But obviously a year on the floors are exactly the same.
     
  16. Vienna

    Vienna Member

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    Sorry I meant the magnasite was 15mm thick!
     
  17. dazlight

    dazlight Super Moderator

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    Was going to say that’s not magnesite at 150mm
     

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