John Sayers' Recording Studio Design Forum Archive

Is the third layer of gypsum going to make that much difference for me (I am hoping to track drums) considering I have a masonary outside wall?

And 12 inch air gap... ouch.

Indeed it will.

Losing a few extra inches does hurt. I can relate. I have 10 feet of unfinished width to work with and I'll be lucky to end up with 8 when I'm done. 8 feet wide is really narrow. Yes, it's expensive in terms of lost space. However, if you build it without sufficient mass or air gap, it may be even more expensive in terms of lost use.

--Keith

And I start counting the airgap from the edge of the joists with the insulation, not from the edge of the plasterboard I am guessing... so my walls will end up being about half a metre thick in total :S

I don't think so. If we talk about walls, you count (in my case) from the inside of the cement block wall to the BACK of the first layer of dry wall. The thickness of the studs doesn't matter (for calculation purposes anyway). So if you're talking about ceiling joists, you'd measure from the back of your first layer of drywall to the closest face of the ceiling.

Hope you're less confused after reading that than I am after trying to explain it.

len

Len's right. You can "ignore the studs" when it comes to measuring the air gap. For example, double 3 1/2" frames only 1/2" apart yield a 7 1/2" air gap.

http://www.johnlsayers.com/phpBB2/viewtopic.php?p=21902

Check out the sketch, "Block Wall Variations, near the top... Steve

100% perfect info. Thanks.

So is the insulation less important than the drywall? I would get a bit less insulation and another layer of drywall if that's the case.

If you can post the two constructions you want to compare, I'll do rough calculations for you... Steve

Well it's just a matter of trying to decide how much insulation and how much plasterboard to use, so I dont really know what options to give you.

25cm gap between plasterboard and wall. Studs with some insulation in (does this affect the sound transmission much? Am I best putting almost zero insulation in and lots and lots of plasterboard?)

Given the exact same total thickness, here are a couple of examples of same total thickness walls using masonry outer leaf, gypsum inner leaf, and .8 PCF normal spun fiberglass insulation in the cavity; both walls are exactly 300mm thick total.

1) 100mm concrete solid block outer wall, 175mm air/insulation, 2 layers 12.5mm gypsum - STC 76, with TL no worse than 50 dB @ 50 hZ, m-a-m resonance of 36 hZ.

2) 100mm concrete solid block outer wall, 150mm air/insulation, 4 layers 12.5mm gypsum - STC 81, with TL no worse than 53 dB @ 80 hZ, m-a-m resonance of 29 hZ.

The second wall with its more balanced leaves, and more mass on the inner leaf, gives better results across the audio spectrum - however, when I increased the concrete to 150mm at the expense of 50mm less air gap, the low end went to hell - down to about 46 dB. So #2 would be your best bet;

Another option would be using 3 layers of 15mm gypsum; same total wall thickness, this gives STC 80 with 53 dB TL at the low end, and less labor putting up three layers of gyp instead of 4... Steve

I did 3 layers between on my Drum room wall. and isolation is EXCELLENT!!!!!!!

Are you filling the entire cavity with fibreglass insulation? I am not sure I can afford that...

Not necessary; you can use an adaptation of this method

http://www.johnlsayers.com/phpBB2/viewt ... 3&start=30

(check my post on Nov.

And just use slightly thicker than stud depth, retained against the gypsum by the strapping across the studs.

If you're using wood studs, build the frame on the floor first, fasten the strapping across the backs of the studs using large head roofing tacks (at least 1" long) then stand the frame up, fasten in place, insulate, and put the gyp layers on... Steve

Excellent, perfect information again. Many thanks.

Just thought:
Would I just be better off building the inside wall out of bricks or concrete blocks again? Seems much denser and cheaper than 4 layers of plasterboard...