# Forum Home Renovation Plastering  Double gyprock Vs insulation???

## Rhino666

I having a builder put up a couple of interior walls in an office space. Sound proofing is important so we added sound batts to the walls. One of the interior walls(3m high 8m long) was existing and had no insulation. Is it better to just add another layer of gyprock or take off one side and add insulation before re-plastering??? Obviously the second option is more expensive but will it be a lot more sound insulated having 2 layers of gyprock and insulation vs 3 layers of gyprock???? 
Secondly, how much sound travels over the wall through the ceiling. I have those plasterboard tiles with about a 900mm cavity in the ceiling. How important is it to insulate the ceiling cavity?? 
Thanks

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## Koala-Man

I looked at this a few weeks ago (done nothing yet of course) and my builder brother suggested just sticking another layer on top of the existing plasterboard rather than ripping the wall open and stuffing it with batts. 
But - this is the important bit - he also said it would be much, much better to use the products that are designed to cut the noise. The stuff's called Soundstop (Boral) or Soundchek (CSR Gyprock) and maybe there's some other versions. 
It looks like normal plasterboard but it's heaps heavier and denser. Their respective web sites have the specs. If you want to get tricky you can batten it out so there's minimal contact between the layers - they have special fasteners for that. 
I don't know how that compares with doing it the proper way with batts as well, but unless your neighbours are as noisy as mine it's probably no big deal. 
You might have to order it in from your building materials supplier, after first having the guy behind the counter, who's stone deaf from listening to talkback radio at 250db for the past 40 years, sneer at you like you're an idiot for even asking. 
This was my first post. It hardly hurt at all.   :Biggrin:

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## pawnhead

If you're going to remove the wall lining, then the most effective way to soundproof is to remove the noggins and install an extra row of studs with an airspace between the adjoining wall lining, and feed insulation in a continuous zig zag along the wall as so:    
With this method, vibration from one skin won't transfer to the other skin as readily. 
Edit: Welcome to the forums Koala-Man. It's a good place to hang out.
Some good advice from you there as well.  :2thumbsup:

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## Rod Dyson

See some post below and you will get a better understanding of sound proofing.  It consists of 3 parts and to be effective you need to address all 3.  Density of the wall lining. Isolation eg, wall cavity and setting up a barrier with resilient clips.  And finally sound absobtion, that is the insulating material. 
Sound check plasterboard is a rip off in my opinion, equal density or better in plasterboard can be achieved with other cheaper alternatives.   Go to this web page and you can compare one product with another that have been tested.  http://www.how2plaster.com/sound/compare.html 
Each step you take will achieve some degree of success.  You need to ask yourself, "How important is sound proofing in this aplication"?  If it is very important then I would add another skin on the existing wall using resilient clips mounted on a packer that would allow you to install 50mm sound insulation.  I would then line this wall with a minimum of 13mm fire rated plasterboard.  The 13mm fire rated plasterboard will give you more "bang for your buck" than any other product.  
Then I would put a double layer of the best quality sound insulation you can buy in the ceiling space, for 1.2 meters either side of the wall. 
This I believe will give you a very good out come for a reasonable price.  To get a better outcome you would need to pay more attention to the ceiling.  Regardless of what more you did to the walls you will loose it in the ceiling. 
Hope this helps. 
Cheers  
Rod

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## Rod Dyson

Pawn head the system you have described is very effective but not the cheapest option to get a good result in this case.  It addresses all the issues but would be more expensive and less effective.  Primarily due to the fact that by putting the furring channel over the existing plasterboard and adding another layer of plasterboard you are creating 2 cavities and increasing the density by one layer of plasterboard.  Yet still achieving the reduction in sound transfer.  Which can all be done without any demolition and removal of the existing plasterboard. 
Cheers Rod

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## cflake

Along similar lines, I own a house that has no insulation. We like the idea of sound proofing as a side effect of insulation, but our main aim is to reduce our heating/cooling bill. I have started on one room and have pulled all the plasterboard & levelled the walls and about to install batt insulation & new plaster.  
To do the whole house (all the external walls) will be a big job. Rod, do you think we would be able to simply whack another layer of plasterboard over the current instead of insulating the walls?

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## Rod Dyson

No, a second layer of plasterboard will only marginally change the thermal rating of the walls. 
It is the insulation trapping heat/cold in/out of the cavity that gives you the thermal rating.  
Density alone will not achieve thermal results.  
Have you thought about pumping in isulation down the wall cavity, rather than taking off  the plasterboard.   
I have not had personal experience with this, but it would seem to me as a better alternative. 
Perhaps someone else may comment on this option.

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## cflake

> Have you thought about pumping in isulation down the wall cavity, rather than taking off the plasterboard.

  I've thought about it ... a lot!  But can't find anyone who actually does it in Australia and I don't know how effective it would be - I suspect it's pretty easy to miss a spot & leave a void.

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## pawnhead

> I've thought about it ... a lot!  But can't find anyone who actually does it in Australia and I don't know how effective it would be - I suspect it's pretty easy to miss a spot & leave a void.

  I found the following links in this thread.  http://www.foamedinsulations.com.au/ http://www.greenhouse.gov.au/yourhom....htm#retrofits http://www.retrofoam.com/

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