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Cavity wall insulation in ceiling?

Discussion in 'Home Cinema Buying & Building' started by binbag, Jun 9, 2005.

  1. binbag

    binbag
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    I'm thinking of getting the company that did my cavity walls to blow the glass fibre fluff they use into the ceiling above my HT as sound insulation to the bedroom above. Has anybody tried this? I'm wondering how effective it would be, what effect it would have on the heat transfer between levels and did it present any unforseen difficulties?. There is no insulation there at present.
     
  2. mattym

    mattym
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    i dont know about the heat, but it wont really make much difference to the sound transfer...you might find it muffles the sound slightly...
     
  3. Van300

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    It may help a little but probably not worth the cost and hassle unless you want to spend serious money trying to sound proof your HT. Unfortunately, sound dampening is very difficult to achieve due to flanking transmission.

    The insulation would also lessen heat loss from HT to bedroom above.
     
  4. binbag

    binbag
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    OK, How about a really thick, dense underlay on the bedroom floor instead?
     
  5. mattym

    mattym
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    you can put a dense rubber flooring under the carpet, but it will only muffle the sound, it wont soundproof it
     
  6. Gary Lightfoot

    Gary Lightfoot
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    Probably not an option, but another layer of plasterboard on the ceiling below will help a little - possibly around 3dbs drop. Combined with rockwoool under the floor it may add a further 2 or 3 dbs. You should also seal all gaps in the floorboards and around the skirting. All this will help with higher frequencies but not with deep bass. Bass can travel via the mass it touches, so you can never truly stop it unless you isolate one room from the other.

    If fixing another layer of plasterboards to the ceiling isn't viable, you could lay strips of plasterboard between the joists remove floorboards to do this) and fill any gaps between the strips and joists, so they will act as a second layer below the floorboards. Then add the rockwool and use silicon rubber sealant to fil all floorboard gaps and gaps at the skirting. Then use a thick rubber carpet underlay as suggested.

    Gary.
     
  7. Van300

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    If you are determined, you can minimise bass from hitting the walls and flanking within your HT. You would need to use two layers of dense plaster board to all HT walls with 100mm gap (filled with 50mm rigid acoustic insulation)using metal studs supported at head and base- not wall otherwise flanking sound will ensue. The ceiling would need like wise and floor would have to be reworked so that the floor sits on top of acoustic pads to stop flanking sound and the door/s would need to be dense with soundproofing strips/seals.

    Essentially, the HT would need to be as an isolated and air tight box/space. Of course you would need to add as much acoustic insulation as you can to the bedroom floor along with absorbing ,materials to the HT such as very thick hung cloths etc to absorb the sound. Unfortunately, the finish has got to be completely air tight as any holes would ruin the sound deadening effect.
     
  8. binbag

    binbag
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    Lets try this from a different angle...

    What is the best value solution to reducing the noise from my HT to the bedroom upstairs? The ceiling is plasterboard with inset lighting and the floor upstairs is chipboard. Between them is an 8" airgap. I'm not looking at spending more than £150 or doing more than lifting floorboards upstairs.

    If you could frame your answers with percentages of effectiveness (100% being total silence) I'd be grateful as I'm not familiar with decibel calcualtions.
     
  9. pjskel

    pjskel
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    Scrunched up newspaper? 3%?
    Well, you are limiting yourself to £150!
    Spend £500 and you could produce a minimium of 25% drop using some of the ideas mentioned above.
    Bass rumble will still get through in the absence of an isolated room, but the mids and highs will be reduced by at least 25%, if not more.
     
  10. clarky78

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    Are these sugestions also viable for party walls?? We just bought a house and we can hear the neighbours tv though the wall, so i'm paranoid about setting up my AV system. The house is brand new so i assume when built it would have rockwall or something in the party walls anyway, but this is pathetic. I hate ti think i'm gonna end up boxing my av up till i move house :(
     
  11. Van300

    Van300
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    Clarky, your party wall should comply with Part E of the building regulations for noise transmission. You can have it tested by an approved acoustic engineer and if it fails you will have a strong case for corrective work and compensation from the developer.

    Or could it be that your neighbours are partially deaf?
     
  12. clarky78

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    How do i go about that? just look in the yellow pages? Assuming it's all correct, i'm thinking of getting rockwall blown in, is that expensive?
     
  13. Van300

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    Ask your local building control officer. They should have the original application and will be in a position to give you details re what the party wall construction is/should be.

    You could explain how bad the acoustic is and they may investigate further.

    Having insulation blown in should improve it marginally but you should ask building control and your neighbour on this too as it is a party wall. I don't think it will be expensive to carry out- circa £500.
     
  14. spamboy

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    When I was re-doing a floor in our house (located above one of the bedrooms) I put in high density rockwool and I found that the effect at stopping high frequency noise (such as speech) was impressive. Once I added a carefully sealed floating floor on top of that the sound transmission dropped again, but I think that the rockwool will help you with everything apart from the bass and impact noise.

    I'm certainly planning to have rockwool blown under the floorboards of the room above my home cinema (I can't be bothered to take all the floorboards up.) No idea on the cost though, haven't really looked into this yet.

    Also once green glue becomes available in the UK I plan to add another layer of plasterboard with green glue onto the ceiling, this is to control sound leaving the home cinema, rather than entering it though.
     
  15. clarky78

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    We looked into getting an engineer round to test the acoustic dampening of the walls, but it was going to cost £2000 :eek:

    Looks like i'm gonna have to live with it, unless we can persuade the builders to prove it themselves.
     
  16. Van300

    Van300
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    Clarky

    Ask your local building control officer what the party wall construction is rather than have it tested! If you let me know what the construction is then I can let you know whether it complies. If it doesn't then you can notify your building control officer and take things further. Usually, the builders are required to carry out 10% testing minimum.
     
  17. Mad Mr H

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    Answers to original thread first,

    RE noise from downstairs getting into upstairs bedroom.

    I will asume the following

    System is 5.1 audio and you use it at a sensible to loud level

    First thing is to be more specific to the "Noise" you hear upstairs....
    Mainly bass, clear vocals, very clear hi-hats?

    If you hear vocals and hi hats you have a major problem and almost ANYTHING you do will help,

    My ideas (opinions - as usual) are as follows.

    1. Your chipboard floor is difficult to get into, but NOT impossible, "TREND" do a clever cutter which cuts access holes in a chipboard floor and is as rong as the original floor - my opinion the best and only way to deal with new style house builds. rent a router, buy the access bits would cost you about £60 to do an average room for FULL access - This is useful for adding cables as well and well worth thinking about. - will help if you need to run any cable in this space for your HT.

    2. Chipboard floor means you cant get FULL access to add plaster board in the floor line, your £150 means a new ceiling is also out.

    3. consider a wood floor to the bedroom? that would at least create a similar idea to the additional plasterboard. and a cheap option these days.

    4. take a look at your HT room, Im guessing the entire house is chipboard floors, spike the speakers, raise them up, isolate the bass from the floor. give some thought/time to this room FIRST, try things and see what the results are, move speakers out of corners, move the bass away from a wall.

    ALL too often people try and "repair" the final issue and dont think of the cause....

    I hope this has been food for thought for you.
     
  18. Docta teef

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    I used high density slabs in the ceiling between my cellar conversion and living room a double layer made about a 10dB difference when tested apart from parts of the room where i knew there would be sound leaks. Given the age of my house the living room has exposed wooden floors and that dont help i would think getting the thickest underlay or ever acoustic matting upstairs may work better with a nice shag (carpet)
     
  19. Hudson

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    I have not long had a bedroom extension completed above my HT room, and i too thought about extra sound insulation for the bedroom that i now above the room. i had two pieces of dense plasterboard fitted to the HT room ceiling, before this i had the builders fill the joist void with acoustic rockwool (they did not like this, heavy, itchy, and awful to work with). I then made sure all the gaps on the new chipboard floor upstairs were sealed. I added a high density underlay and then carpet. Although you can still hear the system it is no where as bad as i thought it would be. I had the advantage of pulling the HT room to bits for the extension. Unless you spend some serious money/pull the place apart, i am not too sure you will be able to achieve exactly what you want. Go for the rockwool between the roof and floorboards and a dense flooring material in the bedroom, i would say this could be your best bet.
     
  20. clarky78

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    Update to my problem. Just had the builders around today to take some bricks out the end of the house to check the cavity. They were just a bricky and a joiner and with no specific training the had been told by the head office to make sure there is a clear gap 3" wide for the cavity with no debris or mortar touching. This was all they did. The ends of the cavity have some soft type padding concealed in a blue polythene material, that appharantly meens that the sound entering the cavity bounces along the empty cavity and is abosorbed at the end by this material. Well it obviously doesnt work! I would expect the party wall to have been full off sound insulation, not just a bit either end! I'm losing patience now.... Back to NHBC....
     

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