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Cavity Wall insulation advice - can it be done yourself? Damp?

Discussion in 'Building' started by StopHammerTime, 30 Mar 2021.

  1. StopHammerTime

    StopHammerTime

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    Hi

    I've got an issue with flanking noise down my cavities so I've been looking into blown rockwool cavity fill. I really don't see how this doesn't bridge the cavity and bear the potential issues with damp ,yet people seem to do it. My walls are actually rendered and with the above in mind....is there anything to stop me filling my wall cavity myself with rockwool slab? I've got easy access from the very large window reveals all the way back to the party wall. If it's the same difference as a company turning up with the rockwool pump I think I may aswell do it now, even though I would've picked insulated render over cavity fill if not for the noise issues.
     
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  3. Notch7

    Notch7

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    Unfortunately wall ties will stop you.
     
  4. StopHammerTime

    StopHammerTime

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    I'm not sure... they're pretty sparing on this build! Think they were keeping all the metal for the spitfires.

    Fair point, there are a few - in theory though, is there any difference between me bridging the cavity with rockwool slab and a company stuffing it full with blown rockwool?
     
  5. Mag2.0

    Mag2.0

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    I looked at having my cavities filled with blown granular insulation. I have a post ware 1950's property with a low damp proof course (just a thick mortar bed, no signs of slate) I was advised against it for the very reason of bridging the cavity.
     
  6. StopHammerTime

    StopHammerTime

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    That was my next question, I'm already dubious about bridging the cavity further up the wall where penetrating damp could occur - but how do they stop it slippng down between the dpc and bridging it there where you have the water table to contend with?
    It's actually one reason why I thought affixing slap insulation myself above that line might not be too mad an idea
     
  7. Mag2.0

    Mag2.0

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    The installation team suggesting installing a french drain to the perimeter of the building to prevent moisture sitting on the outside skin of brickwork and therefore reduce the risk of moisture saturation.
    I did'nt go ahead with the install in the end as my house couldn't accommodate the french drain.
     
  8. Bullet-Proof_Biscuit

    Bullet-Proof_Biscuit

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    Interested in this topic also I am..
     
  9. KenGMac

    KenGMac

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  11. Harry Bloomfield

    Harry Bloomfield

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  12. SpecialK

    SpecialK

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    I have the white blown in stuff in my cavity. No problems so far after 10 years.. I'm assuming its water resistant so doesn't allow water to bridge?
     
  13. JohnD

    JohnD

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    I have blown fibre. I found some excess in the loft and behind kitchen units where the brickwork is gappy and put it outside in a bucket.

    Rain filled the bucket but when I lifted the fibre out, the water just ran off and left it dry. It has a water-repellent treatment.

    The ordinary loft rolls don't so can get damp.

    The many millions of people who have non-defective walls don't write to the newspapers about having a warm dry house, so of course the stories you read will be from the rare problems.

    I and my neighbours are in an exposed coastal location and have no damp, but the installers have become increasingly careful, over the years, as they can be held responsible if the building is unsuitable.
     
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  14. charliegolf

    charliegolf

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    Isn't the cavity there for a purpose? If yes, why is it ok to ignore that reason and fill it?
     
  15. JohnD

    JohnD

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    Ah, the old "we did it like that 60 years ago" justification.

    I bet your Morris Minor is quite rusty.
     
  16. charliegolf

    charliegolf

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    Mine was a serious Q asked politely. 'We' still seem to do it like that in 2021. Why?
     
  17. Notch7

    Notch7

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    It's a fair point.

    It's not just the cavity space itself, it is the physical separation of inner and outer skins.

    On a cavity wall, on exposed locations water gets through the brick and runs down the inner face of the brickwork. In fact cavity trays work perfectly well if the just penetrate into the cavity enough to catch that moisture. You don't need a cavity tray to go right to the inside skin (although I appreciate the ones you buy do do that).

    Full fill cavity insulation is standard practice for new build so I guess it's been well tested - I've tended to spec Rockwell full fill on my jobs, never had a prob even with the cavity being exposed during the build and the Rockwell getting soaked.

    Retro fit CWI can be risky on very exposed sites. It's not unheard for it to have to be removed.....but then old cavities are only usually 50mm at best and probably full of mortar snot hanging off every wall tie.
     
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