Sound insulation using expanding foam behind dot and dab?

Discussion in 'Eco Talk' started by Flame, Nov 4, 2019.

  1. Flame

    Flame Member

    Hi, i’ve recently boarded and plastered a party wall, the room had been fully redecorated so i do not want to become captain chaos ripping out and insulating, however i can hear next door like never before. I work nights and their whole family seem to move to the bedrooms at 7pm.

    i’m probably not the first to think of it but how effective would it be to drill a series of small holes across the wall and spray expanding foam into the albeit small cavity between the wall and the plaster to reduce the sound?
  2. Jord86

    Jord86 Screwfix Select

    Not effective at all. Expanding foam has very little sound reduction properties.
  3. Jimbo

    Jimbo Screwfix Select

    You need a heavy layer as a reflector and a fiberous layer as an absorber. Or Bose headphones.
  4. Richard_

    Richard_ Active Member

    Out of interest, did you take off the old plaster?

    Also have you changed from carpet to hard flooring?
  5. Flame

    Flame Member

    Jimbo, i actually used to sleep with big red ear defenders on, perhaps i’ll have to reintroduce them to the bedside table!

    Richard, the old plaster was removed and was only a very thin layer, oddly much thinner than the rest of the walls i’ve stripped. I’ve also spent a few quid on a good carpet and underlay so was surprised when things seem to worsen.

    I’ve had a chat with next door unrelated, turns out they’ve put a dartboard upstairs so they’ve been playing with that, hopefully it’s a novelty. Still, worth a shot but looks like i’ll have to adjust to the sound for now, cheers for the replies
  6. Richard_

    Richard_ Active Member

    Removing the plaster makes it worse. A wet plaster or sand-cement parge coat seals gaps between bricks. Also using plasterboard acts like a drumskin.

    You may find sound is coming in below the floor level Often the brickwork between joists is poorly finished.

    The key is:
    • Seal brickwork with plaster or parge.
    • Insulate against the wall with something absorbent such as rockwool
    • Put the plasterboard on battens isolated from the wall.
    • Use soft furnishings in the receiving room
    Flame likes this.
  7. Flame

    Flame Member

    Right, thanks for the info. that’s a big job on a completely finished and furnished room but if the problem persists it’s one i will do. The ceiling downstairs will be coming down in june, do you think it would be worthwhile tidying up the brickwork & adding some rockwool to the party wall side between the joists as well to help absorb any sound between the floor coming through?

    Edit: although a potential bodge as i would not have access to the brickwork, could i batten out 100mm off the existing plasterboard and skim, filling the void with rock wool and sound insulating plasterboard?
  8. Jimbo

    Jimbo Screwfix Select

    Should should certainly help. A heavy weight thick felt would be even better.
  9. Bob Rathbone

    Bob Rathbone Screwfix Select

    The only real solution is to install a stud wall filled with dense rockwool, leave no gaps. The inside of the wall would be better to be plasterboard but a mesh or vapour barrier may be used to support the rockwool. DO NOT fix the studding to the party wall but fix it at floor and ceiling and to the side walls.
    Richard_ likes this.
  10. Richard_

    Richard_ Active Member

    Go for the densest (ie heavy) rockwool you can find. Most brands have a version labelled "acoustic". The slabs tend to be better than the roll.

    Or use a specific sound deadening mater, I think you'll find the costs go up with that sort of thing. But it is only one room.

    This is a good site for the sort of products you could choose. Give them a call

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