My room is made of 2 external concrete walls and 2 internal brickwalls (see photo). These 2 are obviously INSIDE the house. This is a detached house in the country side and the room is in the basement)
Would it be a good idea, before building the isolation layer, with the intention of balancing the brickwalls mass with the concrete ones, to reinforce the brickwalls mass by screwing one or two 15mm layers of drywall on it? If so, is sealing mandatory or screwing the panels covering the walls is enough?
Is this worth the effort?
This is one of the brickwalls in section, the gypsum layer is roughly almost 20mm:
I would appreciate very much some input on this matter.
Thanks for your time
Cheers
Adding mass to a brickwall
Originally posted at johnlsayers.com, topic 14610.
Sonolink, Are those actually holes I am looking at - forming essentially tubes that run through the wall? By this I mean the black ends in the picture do not look like they are a solid entity..... If the answer is "yes" then those are not actually bricks - they would be what is known as terracotta This was an inexpensive way to create a masonry structure that had pretty decent sound isolation in the range of the human voice - the air cavity acting as an isolator..... A question - how thick are the concrete walls?My room is made of 2 external concrete walls and 2 internal brickwalls (see photo). These 2 are obviously INSIDE the house. This is a detached house in the country side and the room is in the basement) Would it be a good idea, before building the isolation layer, with the intention of balancing the brickwalls mass with the concrete ones, to reinforce the brickwalls mass by screwing one or two 15mm layers of drywall on it? If so, is sealing mandatory or screwing the panels covering the walls is enough? Is this worth the effort? This is one of the brickwalls in section, the gypsum layer is roughly almost 20mm: I would appreciate very much some input on this matter. Thanks for your time Cheers
Rod,
thanks for your reply. The bricks are like this one:
http://3.bp.blogspot.com/_-IC5HUwYohA/S ... drillo.jpg
They are hollow although the "tubes" don't run across all the wall. They are sealed by the cement used for each brick. They are more like chambers..
The concrete wall is about double to two and a half times the inner walls' thickness. One wall is solid concrete and the other one (that has the windows) is solid concrete up to 1.60m height. Then there's a layer of terracotta that covers 65cm and then again about 30cm concrete. The middle terracotta layer is (I think) to put in the windows.
Please don't tell me I have to demolish the walls and build them up again :(
Cheers
Well, what's the verdict then? I'm kinda holding my breath here...... :?
Ok never mind, I decided to do it anyway. More gypsum can't be wrong.
Thanks a lot for being so helpful
Sonolink - sorry I got tied up for a while and this was as soon as I could make it back... Those are indeed terracotta blocks.. not bricks.... they were pretty widely used here in the states during the 1930's and 40's due to their excellent qualities for both insulation and fire separation..... This is a single leaf - you can add all the mass (directly) to it you want without a worry......... RodOk never mind, I decided to do it anyway. More gypsum can't be wrong. Thanks a lot for being so helpful
Hi There!
Terracota give some isolation to low range frequencies; adding mass is a must at low range so if u can use some extra space dont use plaster wich is more expensive add a layer of rockwool and build a concret sand filled wall agaist it sandwish like. i suspect the holows of terracota must be all more or less the same size thus getting a drop on its ressonance hz; the further it is from sorce dimmer the cut will be.maybe not a significant cut!?!.
Other aspect is the relevance of forcing the vibration to change from one density material to other so: dont screw, Glue. ( a screw or nail is a sonic bridge for the wave sound to crawl trougth)
Or
Glue open cell foam about 100mm thick 80kg/m3 dense to terracota then glue the plaster plate on foam this plate should not tuch floor
Hope i could help
Actually, a layer of plaster would be a good idea: More mass, low cost, good sealing...extra space dont use plaster wich is more expensive
So is glue...dont screw, Glue. ( a screw or nail is a sonic bridge for the wave sound to crawl trougth)
The resonant frequency of the terracota does not depend much on the size of the air cavities inside it, but rather the density of the material itself. Or maybe I didn't understand what you were trying to say....i suspect the holows of terracota must be all more or less the same size thus getting a drop on its ressonance hz;
That doesn't sound like a very good idea at all! There would be no structural integrity behind the drywall :shock: Also, 80kg/m3 density is too high for good low frequency absorption.Glue open cell foam about 100mm thick 80kg/m3 dense to terracota then glue the plaster plate on foam this plate should not tuch floor
Ok guys,
thanks for the replies :)
I added aprox 2 cm thickness of pure gypsum to the inner side of the inside walls made of terracota (well actually a professional builder did it, hehe). This will surely balance a bit with the two concrete walls. I have also added metal frame for walls and ceiling. I'm busy with electricity now (I don't want to cut into the drywall layer so I'm bringing the juice inside the room through one single hole that will be sealed and then all the installation will be on surface (hidden under the room treatment). When I'm finished I will add the plasterboard. Air chamber will be 11-12 cm thick, plasterboard will be triple layer of 15mm panels (45mm total). I can't afford the Green Glue here in Spain (shipping is outrageous) so I'll have to go without it.
I have been advised to put a self-adhesive rubber membrane between plasterboard layers to lower the plasterboard resonance frequency to 8Hz by the guys that sell the plasterboard. Any thoughts on this?
I got some fiberglass "fluffy stuff" made by Isover. I think it's about 20-30kg/m2. I'll fill all the cavity with it :)
Thanks again for the tips :)
I'll keep you posted
Cheers
Sonolink
Great! that should work.I added aprox 2 cm thickness of pure gypsum to the inner side of the inside walls made of terracota (well actually a professional builder did it, hehe).
Just checking: Those frames are totally self-supporting? They don't touch the existing walls or ceiling at any point?I have also added metal frame for walls and ceiling.
Don't forget to put insulation in there! As tick as you can afford, all 12 cm if possible, provided that your local building code allows it to be that thick.Air chamber will be 11-12 cm thick,
3 layers of 15mm drywall is probably plenty.plasterboard will be triple layer of 15mm panels (45mm total). I can't afford the Green Glue here in Spain (shipping is outrageous) so I'll have to go without it.
What laboratory test publication are they referring to, that shows that this will work? What are the published acoustic properties of this "self-adhesive rubber membrane" that they are talking about? How did they arrive at the frequency of 8 Hz for your wall? I'm not seeing that at all! Theoretically, the MSM resonance of your wall built like that is 28.87 Hz without insulation in the air gap, and 20.69 Hz with the insulation. Nowhere near 8 Hz! To get down to 8 Hz, you'd need to go to four layers of drywall over a 50 cm air gap, with insulation. It sounds like they are just guessing, and don't have much of a clue... It sounds like they are tying to do a poor man's substitute for constrained layer damping, but without any published data on the stuff they are talking about, its impossible to say if it stands a chance of working or not. While that rubber stuff MIGHT work, it also might not. a lot depends on the characteristics of the rubber. And in any case, adding a constrained damping layers does NOT work by lowering the resonant frequency of the entire MSM system: it improves isolation at the resonant frequency of the surface by damping the the resonance, but it doesn't affect the actual resonant frequency much. It lower the Q of the resonance, basically. So the claim by your drywall guys that it will "lower the plasterboard resonance frequency to 8 Hz" is pure garbage. The resonant frequency of drywall is way higher than that, and has very little effect on the MSM frequency of the wall itself. They seem to be VERY confused about how a wall isolates! Adding a thin layer of rubber to a sheet of drywall is NOT going to bring the resonant frequency of the drywall down to 8 Hz! :shock: Some people say that you can use normal roofing felt between layers as CLD, but I don't recall seeing any published figures for that either. So I'd say either go with Green Glue, which has been tested and is known to work, or don't do it at all, or just put on an extra layer of drywall and increase the air gap, if you are concerned about total isolation or MSM resonance. And I'd also say you can safely ignore whatever other "advise" your drywall guys might have to offer you, since what they are saying just doesn't make sense, acoustically.I have been advised to put a self-adhesive rubber membrane between plasterboard layers to lower the plasterboard resonance frequency to 8Hz by the guys that sell the plasterboard. Any thoughts on this?
30 kg/m3 would be fine, but 20 is a bit too light. - Stuart -I got some fiberglass "fluffy stuff" made by Isover. I think it's about 20-30kg/m2. I'll fill all the cavity with it
Stuart,
Thanks for your reply and advice
They are indeed. They don't touch the original room at all, except for the floor, where there is a layer of rubber under the metal frame.Just checking: Those frames are totally self-supporting? They don't touch the existing walls or ceiling at any point?I have also added metal frame for walls and ceiling.
No I won't forget :) I intend to fill it all up.Don't forget to put insulation in there! As tick as you can afford, all 12 cm if possible, provided that your local building code allows it to be that thick.Air chamber will be 11-12 cm thick,
I think they were just trying to sell me something more :)So I'd say either go with Green Glue, which has been tested and is known to work, or don't do it at all, or just put on an extra layer of drywall and increase the air gap, if you are concerned about total isolation or MSM resonance. And I'd also say you can safely ignore whatever other "advise" your drywall guys might have to offer you, since what they are saying just doesn't make sense, acoustically.
Maybe I can put twice the amount and press it in a bit (I already bought some)? Or use 40kg/m2? Cheers30 kg/m3 would be fine, but 20 is a bit too light.I got some fiberglass "fluffy stuff" made by Isover. I think it's about 20-30kg/m2. I'll fill all the cavity with it
I wouldn't force it in: You could end up creating a flanking path. 40 kg/m3 is probably fine. I'd go with that. - Stuart -Maybe I can put twice the amount and press it in a bit (I already bought some)? Or use 40kg/m2?
Hi, Terracota with 2cm thick plaster is denser than tree layers of plaster stagered mounts and another tree layers. One wouldnt believe the traction power the drywall would sustain once glued, milion more than nailed. even in cielings (try to rip a sandwich of maybe 2 square inch of 20/30kg/m3 between two same size drywall chunks) But if u want to outcome my sugestion post bether one's i'm not trying to prove anything. drywall must no tuch floor so it can vibrate the density of foam should be maybe 60, insist in 100mm thikness ( maybe 2 drywall plates to get lower hz vibration). I'd go sealing every layer of material all over the room shell in shell like all the way up to second layer of foam second leyar of drywall on floor could be 120/160 foam 2cm thick mdf and glued wood floor but im a low budget musician what can i say! i've helped build two studios for friends they still happy with it glad i could help!Actually, a layer of plaster would be a good idea: More mass, low cost, good sealing...extra space dont use plaster wich is more expensiveSo is glue...dont screw, Glue. ( a screw or nail is a sonic bridge for the wave sound to crawl trougth)The resonant frequency of the terracota does not depend much on the size of the air cavities inside it, but rather the density of the material itself. Or maybe I didn't understand what you were trying to say....i suspect the holows of terracota must be all more or less the same size thus getting a drop on its ressonance hz;That doesn't sound like a very good idea at all! There would be no structural integrity behind the drywall :shock: Also, 80kg/m3 density is too high for good low frequency absorption.Glue open cell foam about 100mm thick 80kg/m3 dense to terracota then glue the plaster plate on foam this plate should not tuch floor
Ok guys, thanks for the replies :) I added aprox 2 cm thickness of pure gypsum to the inner side of the inside walls made of terracota (well actually a professional builder did it, hehe). This will surely balance a bit with the two concrete walls. I have also added metal frame for walls and ceiling. I'm busy with electricity now (I don't want to cut into the drywall layer so I'm bringing the juice inside the room through one single hole that will be sealed and then all the installation will be on surface (hidden under the room treatment). When I'm finished I will add the plasterboard. Air chamber will be 11-12 cm thick, plasterboard will be triple layer of 15mm panels (45mm total). I can't afford the Green Glue here in Spain (shipping is outrageous) so I'll have to go without it. To say that the air chamber shouldt have only air, fix some absorber inside so it does not create a ressonator cavity (Low density rockwool) Spain ships Arkobell to Portugal and im sure there is a similar product as green glue... ill check on it I have been advised to put a self-adhesive rubber membrane between plasterboard layers to lower the plasterboard resonance frequency to 8Hz by the guys that sell the plasterboard. Any thoughts on this? Has it adhesive on two sides? I got some fiberglass "fluffy stuff" made by Isover. I think it's about 20-30kg/m2. I'll fill all the cavity with it :) Thanks again for the tips :) I'll keep you posted Cheers Sonolink
Actually, thickness does not affect density (density is a property of the material itself), and there isn't all that much difference: density of terracotta is around 1900 kg/m3, and density of drywall is around 1200 kg/m3. So those six layers of 5/8 drywall are roughly the same mass as 3" of terracotta. That's a pretty good balance. But what is your point? There's plenty of mass and distance in there to get the resonant frequency down low enough.Terracota with 2cm thick plaster is denser than tree layers of plaster stagered mounts and another tree layers.
Glued to insulation batts???? :shock: And how exactly will "traction power" (whatever that is) manage to support the ceiling on only drywall and insulation, with no studs? The huge weight of that ceiling would simply crush the walls.One wouldnt believe the traction power the drywall would sustain once glued, milion more than nailed.
Sure, no problem: Build it as a proper decoupled two-leaf MSM wall, using the beefed-up terracotta as one leaf, then build a stud frame a few inches away and put two or three layers of 5/8 drywall (as needed) on only one side of that frame, nailed or screwed and NOT glued (never!), put fiberglass insulation in the cavity (around 30 kg/m3), and do the MSM ceiling likewise, with correctly dimensioned joists spanning the inner-leaf top plates and supporting two or three layers of 5/8 drywall for the ceiling, with insulation on top.But if u want to outcome my sugestion post bether one's
Garbage! The entire inner-leaf will vibrate, including stud frame and drywall, and it will flank to the floor. The purpose of caulking the gap is to seal the wall airtight, not to decouple it from touching the floor!drywall must no tuch floor so it can vibrate
No, it should be around 35 kg/m3 if it is fiberglass, or 48 kg/m3 if it is mineral wool.the density of foam should be maybe 60,
Depends on the depth of the air gap, and the local building code. Theoretical ideal is to fill the entire cavity, but as Rod has pointed out that may not be allowed by code.insist in 100mm thikness
That's about the only part you got right!I'd go sealing every layer of material all over the room
A floating floor????? On 160 kg/m3 insulation???? With a single thin leaf on top????? :!:on floor could be 120/160 foam 2cm thick mdf and glued wood floor
It already is a resonant cavity, and that's the way it is supposed to be! That kind of is the entire purpose of building an MSM wall! Putting insulation in the cavity does not prevent it from being a resonant cavity: it just damps the resonance, reducing the Q, lowering the resonant frequency, and improving the isolation.To say that the air chamber shouldt have only air, fix some absorber inside so it does not create a ressonator cavity
No, if it is rock wool, it should have a density of 48 kg/m3.(Low density rockwool)
There isn't. There are some claims, but no published data from reputable acoustic labs. So far, GG is unique.im sure there is a similar product as green glue...
Nuff said. - Stuart -but im a low budget musician what can i say! i've helped build two studios for friends they still happy with it
"Some people say that you can use normal roofing felt between layers as CLD"
I have never heard that before, but as a barrier to sound it is very productive.
Anyone knows what's roofing felt called in spanish? And what's CLD, btw?
Cheers
Roofing felt is "fieltro asfáltico" (in Chile at least).
And "CLD" means "Constrained Layer Damping". That's the principle that Green Glue is based on (and also the fieltro asfáltico).
- Stuart -
http://recording.org/studio-constructio ... ue-10.html "damping material sitting on top of something is called "extensional" damping. extensional damping is massively inept/inefficient at damping thick/stiff/heavy structures. 5/8" drywall would constitute a structure far stiffer than is almost ever damped in this manner." http://archive2.avsforum.com/avs-vb/arc ... 21644.html "The attached graph shows this, but remember that is the best case that we have encountered, most of the asphalt materials do worse, often much worse." Both above comments were quoted from Brian Ravnaas (Green Glue's Technical Innovations Manager). Topical contributions by Rod Gervais and Eric Desart. Tar paper, felt, is neither visco or elastic, but it does have mass, at least a 30# layer will have some mass compared to 15#. But the cost far outweighs any gain that might yield from this practice. That said, if you have it you can use it, but don't go out and purchase a roll. But do not expect it to work as a VE. I recognize that this product (felt) has been bally-hooed in speaker development as a means to this end. The requirement is to glue the paper, both sides, and install it between the speaker cabinet enclosure boxes in an attempt to shear, but attempting this on a wall with no connections being made to secure the sheathing, well, that is fiction.That's the principle that Green Glue is based on (and also the fieltro asfáltico).
I found out it's called "tela asfaltica".
Stuart, would you advise against building my walls and ceilings with it?
Terracota brickwall / Air gap filled with 40kg/m2 fiberglass / 2nd leaf made of 3 layers of 15mm drywall with "tela asfaltica" in between each layer (drywall/tela/drywall/tela/drywall)
Cheers
Sono
To be honest, I agree with Brien: I wouldn't really bother doing that, unless you happen to have some lying around. There really isn't any good substitute for Green Glue, as far as I know. And with three layers of 15mm drywall over a large air space, you already have pretty decent isolation. So if can, then get GG, and if you can't, well, you can always add more mass...
- Stuart -
Ok, I'll follow your advices :)
I'll report back soon :)