Can I plasterboard the other side of my walls?

I am (still) building a studio in my garden. It is an irregular 6 sided building, about 55m2. The outside is dense concrete block, and there is a wooden slanting roof. I am trying to build the room inside the room, however was wondering if I could double plasterboard my walls on the side of the concrete blocks, then fill the stud wall with insulation and cloth over it to prevent the rockwool polluting the air. Will this have any negative isolation effects? If I put plasterboard on the inside as well of the outside of the studded wall, have I just created three leaves even if it's insulated in the studding?

I believe you would create the third leaf if you did that. I wouldn't worry about polluting the air with rock wool since the room-in-room approach should leave you with a (close to) air tight structure. Put the plasterboard you were going to put in the concrete block side as an additional layer on the inside and you'll improve the proformance. len

YOu didn't mention whether your blocks are solid or hollow - if hollow, they form a 2-leaf wall by themselves. Adding drywall AGAINST the blocks would only make this into a HEAVIER 2-leaf wall. Insulation (other than useless closed-cell foam types) counts as AIR for purposes of figuring the number of leaves. If you use hollow concrete blocks, then build a wall frame with both sides paneled, you would have the outer half of block (leaf 1) the air within the block, the inner half of block (leaf 2) the air between block and panel, the outer panel (leaf 3), the insulation(air) inside the stud frame, and the inner panel (leaf 4) If you can BLOW thru it, it's "air" - even a small gap of a couple millimeters will cause SOME multi-leaf symptoms - for example, placing two 12.5mm gyp panels 2mm apart would give a resonance of around 600 hZ, and the TL at that frequency would be weaker by 2-3 dB than at nearby frequencies. 5mm air gap between the same two panels would lower the resonance to around 400 hZ, and 25mm gap would drop it to around 180 hZ. HTH... Steve

The blocks are solid. I am not sure I explained myself properly, so I am sorry about that. I have drawn a picture to summarise... What I am wondering, is if I can put my plasterboard in that position, as opposed to on the inside of the stud wall (which is more usual). Am I giong to suffer much, if any isolation loss by doing that? The stud wall would be full of insulation regardless of what side I put the plasterboard.

hi there

shutupandshave wrote:

What I am wondering, is if I can put my plasterboard in that position, as opposed to on the inside of the stud wall (which is more usual). Am I giong to suffer much, if any isolation loss by doing that?

also i am a total nerd concerning studio building, it seems that steve answered a similar question in the following thread http://www.johnlsayers.com/phpBB2/viewt ... 3&start=15 and also look at: http://www.saecollege.de/reference_mate ... /Walls.htm hope that helps that would be the first time i could help on that forum, so far i got the help from others :D

You explained yourself just fine; but perhaps I gave too much information and confused the issue instead of clarifying. 2-leaf walls are the most efficient use of material for sound isolation - they work on a mass-spring-mass principle, usually called mass-air-mass (air acts as a spring) or just m-a-m. Things that make walls better - more mass in either leaf, wider air gap between the two leaves, better damping of either leaf, minimizing air flow within the wall. The MAIN things are mass, and the width of the air space between leaves. If you put plasterboard on the side of the inner frame that's TOWARD the masonry, you should NOT put plasterboard on the OTHER side of the frame; this will create a 3-leaf wall, and it will flush a fair part of your budget down the drain, taking with it several dB of isolation. If you put your plasterboard on the INSIDE of the inner frame, you will maximize your air gap between inner and outer leaf and improve performance by around 5 or 6 dB. You didn't mention any dimensions in your earlier post, but if you use 100mm solid concrete block outer leaf/100mm air gap/single layer of 15mm plasterboard, you'd get about STC 68 with TL of around 39 dB @ 63 hZ, and m-a-m resonance of about 61 hZ (hence the weak spot at 63 hZ) - doubling the plasterboard with no other changes would net STC 74, TL of around 44 dB @ 63 hZ, and m-a-m resonance of about 44 hZ (the lower the m-a-m, the better - ideal would be around 7 hZ, but this takes twice the concrete and around 3 FOOT air gap, and building a roof/ceiling to match would be daunting to say the least) Increasing the air gap to 190mm (plasterboard on the other side of the studs) would get you the same performance with only ONE layer of 15mm plasterboard, and a second layer would improve that to STC 79, TL @ 63 hZ of 50 dB, and m-a-m resonance of 32 hZ. About the only downside of putting the plasterboard on the inner side of the frame is having to change the mounting method for inside acoustic treatments - but if you want to be able to play drums without fear, probably even in the middle of the night, it will take all the help you can give. Total attention to detail while building, so you don't inadvertantly couple inner leaf to outer leaf ANYWHERE, and you may just be able to ignore the clock while tracking drums... Steve

I was planning on having about a 10cm gap. Between the wall and the stud walling, and rockwool filling the studding (regardless as to whether or not the plasterboard is on the side of the masonary or not). If I understand what you're saying correctly I am going to lose a few DB of isolation by having the plasterboard on the side of the masonary... I am not sure that's a good idea. I think it is goking to be very fiddly getting the insulation in before I apply the plasterboard. Ah well :(

I dont want to steal this thread but I had rather the same question. I was planning on having: 75mm Timer Stud, filling this with mineral wool, then a resilliant bar on the wood, which I would then mount a Plasterboard and isolation mat sandwhich (PB/Iso Mat/PB) This would be the inner wall and the plasterboard would be on the living space side. I assume I would not want to attach plasterboard to the outer side of this wall where there would be an air gap of about 8" (190mm) before an outer wall. (I think that made sense) Then doing the same and not having a piece of plasterboard on the outer wall so it was the insulation and timber frame, then airspace, then another timber frame and insulation (if that makes sense). Nick

I think it is goking to be very fiddly getting the insulation in before I apply the plasterboard Look for fiberglass strapping material, typicaly used to band boxes for shipping; also used to strap loads to pallets for shipping. If you stretch this stuff across the inner sides of the wall studs at about 1 foot intervals horizontally, it will keep the insulation up against your wallboard and improve damping at the same time. Typical way to accomplish this - build the wall frame on the floor(horizontally) in front of where it will be placed; nail the strapping onto the studs using roofing nails (large head, about 1-1/2" long) - then stand the frame up (if you make it 1/4" shorter than the floor/ceiling distance, it will just clear) - fasten the frame in place, install the rockwool batts (they are stiff enough they should stay put, they need to be about 1/4" wider than the stud cavities) then apply the first layer of gypsum. See Julian's thread for more on caulk, etc - http://www.johnlsayers.com/phpBB2/viewt ... 3&start=15 Nick, not too clear at all; can you post a sketch showing what you intend? Thanks... Steve

This is basically what I was going to build. But without the brick wall. http://www.customaudiodesigns.co.uk/soundproofing/rbars_battening_2.html but this was going to be the second leaf. The first leaf would be a different design but same basics. I am assuming I wouldnt want to attach plasterboard where the wooden frame goes, ie the opposite side to the resilliant bars. Also how well would this construction work, they say it reduces 50db or near. I hope that made sense that time.

That animation shows resilient channel though. :? That isn't needed in your case and may actually worsen things. :roll:

Keith's right Nick, if you have separate frames for inner and outer leaf (or if there's one frame for inner and a masonry, separate outer leaf) then resilient mounts only cost you money... Steve

Excelent, well theres a saving. Im not sure If I can afford a maisonary wall though so would an 8" air gap be enough of a cushion, I could probaboly stretch to a 12" air gap if needed.

12" is way better than 8". If you can afford it, go for it -- especially if you really care about keeping the other side quiet.

Actually, placing 2 layers of 5/8 wallboard (15mm) each side of double frame wall (2x gysum, frame, space, frame, 2x gypsum) with insulation inside the STC for either 8" or 12" air space is about 67 - but for low end, the 12" air gap gets about 42 dB @ 50 hZ while the 8" gap only gets about 39 dB. So if you're doing live drums I'd go the extra depth, and a 3rd layers... STeve

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 :mrgreen:

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