Green glue advice with a dividing wall

Chrisharry12345

Well-known Member
Hi in the next couple of weeks I plan to try and do some sound dampening on the wall between us and our neighbors. I have come up with the following and was wondering if anyone could give any further advice and guidance on what to buy? I will be doing just the one wall between us and the neighbors and the some sort of mats under the carpet. When I do my living room where my full home cinema set up is ill also do the side walls and ceiling to prevent flanking.

It is mainly to reduce the horrible noises coming from the neighbors bedroom routinely at 8.30am on a Saturday morning! Also so I can listen to music and not have to worry too much..

So I plan to do the following.

1. Electrician is coming round to move the existing plug socket on the wall onto a side wall.

2. Build a stud wall decoupled from the existing wall with a 10mm gap using 75mm thick timber. The bottom of the stud wall will be seperated from the floor with these isolators
http://www.eqacoustics.com/products-page/sound-proofing/noise-block-stud-wall-isolators

3. The wall will then be insulated with slabs of 75mm Rockwool sl930
http://www.insulationexpress.co.uk/Product.asp?gclid=CIucy8Dr0b0CFTHItAodpQIAVQ

4. The plasterboard will then be added which is the Gyproc SoundBloc Tapered Edge 2400 x 1200 x 15mm
http://www.jewson.co.uk/building-materials/plastering-plasterboard/plasterboard/acoustic-plasterboard/products/PRBBG583/gyproc-soundbloc-tapered-edge-2400-x-1200-x-15mm/

5. A second layer of plasterboard will be added with 2 tubes of green glue per sheet staggered from the first.

6. A small gap around the edge will be left and filled with Green Glue sealant
Green Glue Noiseproofing Acoustical Sealant

7. Mats to be placed under the carpet something like EQ Acoustics

8. Wall plastered


Ok so I have put this list together based on my research and help from current users who have done similar. I have no background building knowledge and have a couple of questions/ checks..

1. Have I missed anything?
2. Can anyone recommend a product as a better alternative to something I have suggest? In particular the insulation and the matts to go under the carpet
3. What screws/ nails are reccommended for the plasterboard?

Thanks in advance
 
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Mattle40

Active Member
You've got it Sussed pal, all I would add is, never use nails, it's only a matter of time until it pops ur plaster.
And make the second layer of plasterboard different, as it's the change of density which deadens different frequencies.
Iv used knauff boards and chose soundboard plus 15mm then the second layer will be called plank 19mm thick

But good luck, il be watching ur thread ;-)
 

Geps

Well-known Member
And make the second layer of plasterboard different, as it's the change of density which deadens different frequencies.


Does that not relate to free air versus non free air? I'm not sure if it actually relates to densities between two types of plasterboard - last person who said that on here went silent when asked to explain further so I have to be skeptical of that advice.... I think density A is insulation and density B is the plasterboard but I'm happy to be proved wrong....

If you're house is old Chris, I'd strongly recommend you look at where the joists fix into the party wall. You can typically find movement over the years and sloppy construction can leave space around the joist meaning the sounds can go straight through your floor and/or ceiling and completely bypass your wall.
 

Mattle40

Active Member
Geps, I'm no acoustician; but research I have done points to this being true. you feel free to be skeptical and I won't try change your mind. there are a lot of threads discrediting green glues benefits, but I chose to believe that it works. I was simply stating my opinion on a route to go down as the op asked questions on my build thread.
Personally I think it makes sense that varying densities excel. Just my view tho and could well be wrong
 

Geps

Well-known Member
Sorry no, I'm not questioning whether changing densities or green glue works (the latter I believe they have lab data to prove?) but merely the comment of the second layer of plasterboard having to be different.

It's my opinion that whilst it may reduce the frequency response it's so negligible that you'd get more benefit making both layers the same, as you can cut down on waste and add more mass to both layers in the first place.
 

Chrisharry12345

Well-known Member
Interesting point there about different densities, didnt even cross my mind.. are thicker boards supposed to work better with higher or lower frequencies?
 

Mattle40

Active Member
I apologise for missing the disclaimer "in my opinion" from my original post.
That is what research for my own build told me, that is what encon, my acoustic supplier recomends, and knauff make three different acoustic densities for this purpose.
I'm certainly not saying "I'm right, you're wrong" here, but this is my opinion.
 

Mattle40

Active Member
Interesting point there about different densities, didnt even cross my mind.. are thicker boards supposed to work better with higher or lower frequencies?

Geps may correct me here, but higher mass is required for reducing lower frequencies so thicker boards are better for this application.
 

Geps

Well-known Member
Interesting point there about different densities, didnt even cross my mind.. are thicker boards supposed to work better with higher or lower frequencies?

Be careful not to confuse thicker boards with densities. Soundbloc vs normal plasterboard are the same thickness, yet soundbloc is approx. twice as heavy.

I apologise for missing the disclaimer "in my opinion" from my original post.
That is what research for my own build told me, that is what encon, my acoustic supplier recomends, and knauff make three different acoustic densities for this purpose.
I'm certainly not saying "I'm right, you're wrong" here, but this is my opinion.

As I said, I don't doubt different densities work - what I question is that in the 9.5-15mm thickness of a plasterboard sheet, is changing the density by half (normal vs soundbloc) really as beneficial than just going straight to making two layers of soundbloc 15mm and having alot more mass.

What do knauf make in three different densities? They're soundbloc (soundshield) and acoustic rolls all look to be a single density from the quick look I had.

There are already several densities, going from neighbour to Chris' side:
Plaster->Brick->Air gap->Insulation->Plasterboard

Geps may correct me here, but higher mass is required for reducing lower frequencies so thicker boards are better for this application.

I won't ;) not only as Mattle says but there is also the idea that a thicker board is also more rigid, so it flexes less and less flex = less sound transmission. There's a reason cymbals on a drum kit are thin!
 

Mattle40

Active Member
Knauff make sounshield, sounshield plus and plank all for acoustic aplications and all with a different weight per sqm.

Plus I think you have mistaken what I said, I didn't recommend a layer or sound block and a layer of normal.
I'm recommending two different acoustic plaster boards to broaden the target frequency range. If u can agree that varying densities does have merit then surely what I'm saying is a no brainer?
 

Mattle40

Active Member
Geps, just read some of my posts back, may have come across a bit abrupt but all meant in good humour ;-)
 

Geps

Well-known Member
Knauff make sounshield, sounshield plus and plank all for acoustic aplications and all with a different weight per sqm.

Got you - I thought you meant different densities of each board type.

Plus I think you have mistaken what I said, I didn't recommend a layer or sound block and a layer of normal.
I'm recommending two different acoustic plaster boards to broaden the target frequency range. If u can agree that varying densities does have merit then surely what I'm saying is a no brainer?

I see your point but for me, going from like an insulation density to a plasterboard density is different enough to make a difference. I still think when you're talking about mm of plaster, you get far more benefit of upping the mass. It even says in the Knauf manual:
"Knauf Plank is 19mm thick making it a good acoustic ‘mass’ layer" and yeah I did did look that up ;)

There's no evidence either way so I guess it's an agree to disagree end!


Geps, just read some of my posts back, may have come across a bit abrupt but all meant in good humour ;-)
:D

I think to be honest Chris, and I'm sure Matt will agree, if you're doing one wall, the flanking noise will probably be far more of an issue than extra few mm of whichever density (or mass ;)) plasterboard you use.
 

Mattle40

Active Member
Lol il agree with that but I'm still using sound shield plus & plank lol ;-)
I had already had a chuckle at the flanking issue as that's out of my budget to properly address but at least it will stop the old cup to the wall trick working.
Anyways, let's give Chris his thread back :)
My advise stays the same but could well be nonsense haha
 

Chrisharry12345

Well-known Member
Thanks guys an interesting discussion I think if there is no negatives in trying the two different then it cant hurt :)

The flanking thing is annoying me already.. I dont know if I can go digging up the floor but I think I will lay some mats down. As for the side walls we have taken off all the paper tonight and there's some cracks so i'm tempted to just do that wall as well not that I can really afford it!

I have spent most part of the evening trawling through the builders merchants trying to see wheres best to buy the boards and the insulation and got no where!
 

Mattle40

Active Member
If you have an encon near you then they are very useful and well priced, although they can't do a good price on green glue.
Other than that I'd be looking at mail order depending on your quantities
 

Mattle40

Active Member
It does yes, it's actually a handy size for me as my stairs are tricky to negotiate and the 2.4x1.2 sound shield plus boards were a nightmare @ 36kg each!!
 

Chrisharry12345

Well-known Member
I have been looking a bit more into the two different panels and found this direct on the greenglue site in the FAQ's

"Please note: despite reports that using two panels of differing thicknesses (i.e. one 5/8” panel and one ½” panel) will yield a better result than two panels of the same thickness, we have not been able to confirm this. It remains our recommendation that two layers of 5/8” drywall be used whenever possible."
 

Mattle40

Active Member
I just want to confirm, I wasn't recomending varying thicknesses, I'm recommending different densities.
 
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Chrisharry12345

Well-known Member
I know Green Glue is the stuff to get for this but what about there sealant? I can find one supplier in the UK thats £15 a tube... Green Glue is unique compound but is the sealer a similar product to the others on the market?

buygreenglue.co.uk do a sealant called sound sealant for a similar price of £13.20

EQ Acoustics do a "Sound Block" for just £6.99 a tube saying they didnt get on with the green glue sealant.. Any thoughts?

Wood arriving today, Green Glue monday, plasterboard and insulation on tuesday :)
 

Mattle40

Active Member
Thought the same thing my self pal and I'm taking the risk of using a lesser sealant. Still soundproof however but I'm not paying green glue prices twice lol.
Iv got rockwools version at £6 each
 

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