Will 100mm Rockwool soundproof a party wall?

Discussion in 'Builders' Talk' started by TaraWhit, Feb 17, 2020.

  1. TaraWhit

    TaraWhit New Member

    Me again

    Does anyone have experience using 100mm Rockwool insulation for a shared party wall (loft conversion is going up next door to our current loft conversion) and it's effectiveness at soundproofing?

    Thank you.
  2. DIYDave.

    DIYDave. Screwfix Select

    Not great in all probability !

    Easy to use, cheap, and the stuff nowadays doesn’t itch like mad but, soundproofing qualities are limited

    Much better products out there which are designed for the job and more high tech. More involved in the instal though than just ramming in some rockwall

    Insulation ‘batts’ would be better than rockwall as a whole lot denser but specific insulation boards would be your best bet but, again, their installation is critical to achieve best results, otherwise all you do is transfer noise from wall through fixings and back into your wall where the noise becomes amplified

    Others on here will be able to make specific recommendations I’m sure, I’m just talking generally but rockwall, Nahhhhhhh, waste of time
    TaraWhit likes this.
  3. Jitender

    Jitender Screwfix Select

    If its rockwall RA45? then its a lot denser than standard insulation so will give some level of sound insulation.

    You will also want to use sound proof plasterboard as well.
    TaraWhit likes this.
  4. TaraWhit

    TaraWhit New Member

    Thank you DIY Dave!

    Jitender - The shared wall for the loft conversion is only being listed as Kooltherm K-18 dry lining board which isn't sufficient for sound proofing. They have simply listed that the sound insulation for the floor of the loft conversion will be 100mm Rockwool insulation. We want to request further sound proofing between the walls and I was wondering whether to suggest they carry on the Rockwool through the wall as well as the floor, or whether we need to find a better solution for the wall. Am trying to get all my research done before broaching the matter!
  5. Jimbo

    Jimbo Screwfix Select

    The thickness of the fibrous layer basically determines it's effective frequency range. Unfortunately sound travels slowly so has long wave lengths and hence achieving any real attenuation at low frequencies is difficult with just an absorber.

    As stated acoustic rock wool is the correct stuff to use. Then you want something heavy enough to act as reflector in front of it, forcing the transmitted sound back through the absorber. A couple of layers of acoustic plasterboard is one option with a a heavy acoustic mat such as this between them: http://www.soundservice.co.uk/soundproofing_mat_SBM5.html

    The design of the wall build-out needs very careful planning. Sound will be transmitted through any direct bridging points and sealing air movement around the perimeter is absolutely key. So decoupling the surface from the structure using acoustic mounting bars helps (see the link) is required. The wall will also be much heavier than a normal stud wall, 40kg per m2 or more.
    TaraWhit likes this.
  6. TaraWhit

    TaraWhit New Member

    Thank you Jimbo, very helpful.

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