Ceiling Layer Materials

Just a quick question about my proposed ceiling materials. Currently I'm planning to use 2 layers of standard 10mm plasterboard with green glue between the sheets. Would I get a better result if I used 1 layer of yellow tongue with 1 layer of plaster board on top & green glue between them ? Cheers Matt

Hi there not an expert but you will probably get some answers if you add some details to your profile, and maybe a bit more information about your build, however from what i'v learned 10mm plasterboard is not thick enough, minimum to use is 15mm/16mm depending on where you live :D

Adding to that I would ask the Green Glue Folks since what you suggest has nothing to do with what GG was developed for according to the greenglue site :)

Thanks guys. Weight is an issue here, hence 10mm PB & GG. The yellow tongue is way heavier so 10mm plaster board it is. Someone I know has plenty of styrofoam in sheets, I may use this as well as it weighs next to nothing. So looks like I'll go with: Battens >> Styrofoam 30mm >> Ceiling Insulation >> 10mm PB >> GG >> 10mm PB

Hi Matt. Welcome to the forum!

Would I get a better result if I used 1 layer of yellow tongue with 1 layer of plaster board on top & green glue between them ?

Better for what? You don't say what you are trying to accomplish here, so it is impossible to say. Also, you are only talking about your ceiling, not the walls, floor, windows, doors, HVAC or electrical, so you are only telling us about a very tiny part of your build. So there really isn't much that we can say, since you didn't give us enough to go on. In any case, I though yellow tongue was meant for flooring, not ceilings...

Weight is an issue here, hence 10mm PB & GG. The yellow tongue is way heavier so 10mm plaster board it is.

Ummmm... actually, the DENSITY is what matters, and the density of drywall and yellow tongue are practically the same, at around 700 kg/m3 either way. So two layers of 15mm drywall would weight almost exactly the same as one layer of 10mm drywall plus one layer of yellow tongue. And the two layers of 15mm drywall is a tried and proven system the isolates very well, when done properly. The problem with very thin drywall, like you propose, is that it does not perform well as acoustic isolation: it is too thin, too flexible, and the mass is too low. It would be a mistake to do what you are proposing.

Someone I know has plenty of styrofoam in sheets, I may use this as well as it weighs next to nothing.

Not only does it weigh next to nothing, it also DOES next to nothing! For acoustic isolation, at least. It is closed-cell, and therefore useless for acoustics. Only open-cell insulation works. Just to clarify: you do need mass (weight) if you want good isolation, and you do need open-cell damping. Without mass you do not have isolation. Without proper damping, the mass is not working as it should, and the isolation will be lousy. There is no such things as light-weight acoustic isolation. Either it is light weight, or it isolates, but it cannot be both. Isolation is not just a bunch of things that you happen to have lying around, thrown together haphazardly. Isolation is a tuned system, carefully designed using the correct materials in the correct order, correctly installed and correctly sealed.

So looks like I'll go with: Battens >> Styrofoam 30mm >> Ceiling Insulation >> 10mm PB >> GG >> 10mm PB

Battens? :shock: :!: I guess you really don't need any isolation at all, right? So this ceiling is just for decoration, not for acoustics? It really would help if you were to explain in detail what you want to accomplish, because what you are planning so far has no useful acoustic properties at all. Not for isolation, and certainly not for treatment. You would be wasting your time and money if you went down that path. - Stuart -

Not to interrupt ... But I recall doing a little NON scientific testing with 'Styrofoam' ... it seemed to actually AMPLIFY the sound. Ever notice how loud trying to remove an object from a box that is packed with Styrofoam :shock: Also ... isn't it flammable ?!?!

Hi Stuart, thanks for your thoughts. I'm trying to create a tracking room in a home studio. It is not an ideal situation as I'm not designing or creating the space from scratch. Just trying to improve the isolation & reduce the noise of the roof plus some heat isolation as it gets bloody hot. The roof/ceiling is corrugated iron top & bottom of 100mm steel frame with some insulation in the cavity. It is completely useless for recording, heat makes the high tensile design ping & crack as the sun hits the corrugated iron & heats up. Added to this if it rains there is huge amounts of noise. Now, I know this will be impossible to isolate so I'm just looking at getting the noise down to a level where a decent noise floor is achievable The architect has voiced concern at the weight of the ceiling needing to be added, hence my post. I know 16mm plasterboard is the preferred material but this is not possible due to the weight factor. The battens are to be screwed onto the existing corrugated iron ceiling straight through & into the steel pylon/battens in the roof cavity. The batten thickness of 35mm would allow for this cavity to be filled with some other material before the heat film lined insulation is added then 10mm PB >> GG >> 10mm PB Maybe you know of some other materials that be useful ? Cheers Matt

Thanks for the styrofoam facts. It would help with the heat but help the sound isolation is imperative. Looks like a dud material for this job. Cheers Matt

RJHollins wrote:

Not to interrupt ... But I recall doing a little NON scientific testing with 'Styrofoam' ... it seemed to actually AMPLIFY the sound. Ever notice how loud trying to remove an object from a box that is packed with Styrofoam :shock: Also ... isn't it flammable ?!?!

Exactly RJ, it is basically "amplified air" in any configuration. Now as a thermal application in a ceiling it may work but it assumes much as to how the OP is insisting to use it, and my thinking says he is shooting blanks and waiting for a body to fall, if you know what I mean :) edit: "he is shooting blanks and waiting for a body to fall" is the same thing as "throwing something at the wall and seeing if it sticks".

Yes well..thanks for the analogy .. emphasis on anal :lol: Someone suggested sytro as they had a ready supply, bad idea. Mass, I get it.. but as mentioned I'm trying to do a balancing act to get "improved" isolation without loading the existing ceiling too much due to structural integrity limitations. Do you know of any materials that may help me ?

but as mentioned I'm trying to do a balancing act to get "improved" isolation without loading the existing ceiling too much due to structural integrity limitations.

What are the structural limitations? If you could provide those, it would be an awful lot easier to come up with a solution.

I know 16mm plasterboard is the preferred material but this is not possible due to the weight factor.

You seem to have missed the point I was making before about your initial plan of going with one layer of 10mm drywall plus one layer of 22mm yellow tongue: The total mass of that would be practically the same as just using two layers of 16mm drywall. So if the first option was possible within your structural limitations, then so is the better option (acoustically better, since it is proven and known to work) of two layers of 16mm.

Just trying to improve the isolation & reduce the noise of the roof

Treating the roof alone will not give you any extra isolation. Isolation requires a complete envelope, not just one side. You cannot isolate a room by just doing one wall, any more than you can build an aquarium by putting glass in only one side of the frame. You have to do all sides if you want to keep the water and the fish inside. And you have to do all sides of your room to the same level of isolation if you want to keep the sound inside.

The battens are to be screwed onto the existing corrugated iron ceiling straight through & into the steel pylon/battens in the roof cavity.

Then you would not be decoupling the new leaf from the existing two leaves, so there would be very little isolation. In order to isolate, not only do you need mass to stop the sound, you ans need to keep it apart from all existing structures, so that the sound cannot be transmitted mechanically. If you simply attach the drywall to the battens, then all vibrations in the tin roof will be transmitted directly through to the drywall, which will emit them into your room, just like a speaker would. You will still hear all those "pings and cracks", clearly. If you want isolation, you have to decouple the two sides of the wall (or ceiling in this case), such that there are no mechanical connections. In other words, you need to have a resilient connection, rather than a solid connection, and the resilience needs to be tuned to meet the needs of your situation: The simplest method would be to use resilient channel across your battens, and attach the drywall to that. Or as an alternative, RSIC clips and hat channel would accomplish the same thing.

The batten thickness of 35mm

Too thin. The minimum cavity depth you need is 100mm, in order to keep the resilience tuned to a low enough frequency. And even greater depth is highly recommended. 200mm is pretty good. If you only have 35mm, then the MSM resonance will be so high in frequency that your isolation will be very poor. Then there's another issue: you already have a two-leaf roof up there, so your new ceiling creates the dreaded third leaf. For complex acoustic and mathematical reasons, a 3-leaf system will always isolate worse than a 2-leaf system, all other factors being equal. So not only would you have poor isolation from the tiny air gap, it would be compounded by the three-leaf effect.

Do you know of any materials that may help me ?

There are no magical materials that somehow charm their way past the laws of physics. All materials obey the laws of physics. What we are trying to explain to you is the ONLY way to get isolation at reasonable cost and with low mass. All forms of isolation require mass, and lots of it. The method we are telling you about is the one that requires the least amount of mass, since it also uses the phenomena of resonance to help in some parts of the spectrum. You can go with other methods of isolation if you want, using different materials, but they require much more mass than this one, since they don't use resonance as a tool. You could, for example, replace all of the lower corrugated iron sheeting on your roof with 5cm thick steel plating, hung from isolation hangers. But the extreme weight would certainly collapse your building! Unfortunately, there's no way past the laws of physics. You are not the first person to be frustrated by this simple fact: people come here all the time hoping for magic, some type of thin, light, strong material that they can wrap around their room, costing only 5 dollars, and providing 100 dB of isolation at all frequencies! But the truth is that there is no magic. There are limits, and you are butting up against them. Sad to say, your current plan is not going to be very successful. You need mass, and you need decoupling. Basic facts of physics. You have neither. That said, if you give us the numbers then we can give you some advice on what is the way to get the best possible isolation, within the laws of physics. Let us know what the rated live load and dead load for your structure are, and how much load it is carry right now. Based on that, we can suggest optimum materials and methods that you can then take to your structural engineer, for his approval. - Stuart -

Hi Stewart, Thanks very much for the detailed explanation. Here's the edge of the ceiling that runs through to the outside. Steel pylon & insulation visiable from end. https://plus.google.com/u/0/photos/116323250380505709377/albums/5611690904386339473/5611692107156983218?sqi&sqsi&authkey=CNXekfWYgLq0aA So the 19mm particle board & 1 layer of plaster board is your suggestion to help my far from ideal situation. This is the only structal data I have, floorplan of the house & studio. http://matrix-productions.com.au/download/16_Dunnart_Court_Floor_Plan.pdf The studio is being setup in the seperate builing using 1 room for mix & 1 room for tracking. Here's a bunch of photos I took when I was looking at buying the property. https://plus.google.com/photos/11632325 ... kfWYgLq0aA This is the room in question. https://plus.google.com/photos/116323250380505709377/albums/5726403940753714273?authkey=CLaz5_eik4nU0AE I's a very on going project with problems addressed as I go. It would definitely have been better to build a room in a room, but due to the design & materials this wouldn't really work. Adding a second sliding glass door system would of been great but was the quotes were very expensive. I didn't want to alter the house too much from a domestic premises & affect it's resale value. Instead, I created a double layer of cement fibre sheeting & GG between them in the 3rd track of the existing sliding doors/walls on the outside behind the glass. This has helped reduce noise but not isolate by any means. As the suburb is fairly quiet it's made enough of a difference to be usable. The roof is the BIG problem. The steel pylon/battens in the ceiling are 100cm apart so hence the need to use wooden battens as the PB will need to be screwed at roughly 600mm intervals( I believe ?). This then gives us the 35mm( batten depth) cavity which I was initially going to fill with Anticon medium 75mm, this will easily compress & fill the 35mm gap. http://www.bradfordinsulation.com.au/Bradford/UploadedFiles/3c/3ce781f6-944b-4aac-bc6b-bf1425dabc28.pdf The ceiling is sloped & runs back quite low over the door frame. It would only be possible to have a maximum of 50mm cavity due to the door. You can see the door height & the underside ceiling corrugated iron from this external photo. https://plus.google.com/u/0/photos/116323250380505709377/albums/5611690904386339473/5611704912184307826?sqi&sqsi&authkey=CNXekfWYgLq0aA Thanks for your help. Cheers Matt

So the 19mm particle board & 1 layer of plaster board is your suggestion to help my far from ideal situation.

No it is not. I think perhaps you should re-read what I wrote, since you seem to not be understanding it.

This is the only structal data I have, ...

Then it is most definitely time to contact a structural engineer! You can't just go hanging extra mass from existing joists without making sure that it can safely handle the load, and the ONLY person who can tell you if that roof can take any extra load at all, is a qualified structural engineer. If you don't have one, then get one. It would be insane to move forward with this build if it is not checked and approved by an engineer.

Here's a bunch of photos I took ... This is the room in question.

Thanks! That makes things a lot more clear. Unfortunately, I doubt there is much you can do at all to isolate that room. There are just so many issues with it, that it would require a lot of work (and money). It is basically a light weight structure all around, from the foundations up, so isolating it would be pretty hard.

It would definitely have been better to build a room in a room, but due to the design & materials this wouldn't really work.

You are probably not going to want to hear this, but frankly, I would not bother. Anything you do there is going to eat up a lot of money for very little gain. To get the type of isolation that a home studio typically needs, you'd have to start from the ground up, literally. Even if your ceiling structure can handle the extra few hundred kg that you are proposing, the benefit would be minimal unless you also do the walls and floor, and that light weight support structure underneath probably cannot handle the type of loading we are talking about. In fact, where I live, that supporting structure would not even pass inspection: too thin, spaced too far, no lateral bracing, very little strength in sheer, etc. First small earthquake that comes along, that would buckle and the entire house would be sitting on the ground. Fortunately, you don't get earthquakes where you are, like we get them here, so it probably passes code where you are, but there just isn't much ability in that to support any real weight, they type of weight you need for isolating a home studio to legal levels.

I didn't want to alter the house too much from a domestic premises & affect it's resale value.

I would really, honestly abandon the idea of building a studio inside the house, and think more about doing it outside. In one of those photos I think I saw a large garden shed? How about knocking that down and building the studio where it is right now? That would be a much, much better proposition, and would probably be cheaper in the log run than trying to do what you are thinking of doing now.

Instead, I created a double layer of cement fibre sheeting & GG between them in the 3rd track of the existing sliding doors/walls on the outside behind the glass. This has helped reduce noise but not isolate by any means.

Exactly. It won't help much. It can't. There's just too much flanking going on in there, without any stable base or damping. No matter what you do (at reasonable price) the outcome is not going to be good, and won't ever even get close to the level where you could track a band without disturbing the neighbors.

The roof is the BIG problem.

Actually, I'd say that the floor is the big problem, with the roof being secondary. The floor is light weight and suspended over a cavity, with no damping, and since the entire room rests on the floor, no matter how well you isolate the roof immediately above you, you still won't be able to isolate the room itself to the level that home studios commonly need.

The steel pylon/battens in the ceiling are 100cm apart so hence the need to use wooden battens as the PB will need to be screwed at roughly 600mm intervals( I believe ?).

That depends on what your local building code requires, and what your structural engineer tells you. 600mm is probably the maximum spacing allowed, and more like 400mm.

This then gives us the 35mm( batten depth) cavity

You are still not listening to what we are saying: If you go with a very small cavity depth, then the resonant frequency of the new ceiling will be very, very high, and it will not isolate. If you just use battens without resilient channel, then the new ceiling will not isolate. If you want isolation, you MUST decouple, and you MUST have enough cavity depth that the isolation system can actually work. This is not a matter of "what can I fit in", but "what will work". The mathematics of three-leaf systems with two very small air cavities predicts that what you are proposing WILL NOT ISOLATE. It is that simple. Isolation is based on the principles of physics, and there are equations for calculating what will happen when you do certain things: those equations say that a roof such as you propose simply will not isolate, and it will be especially bad in the low frequencies, such as those associated with drums, bass guitar, and keyboards. You can't wish your way around the laws of physics. You keep on telling us why you cannot do things right, and you seem to want to continue on the path you have already chosen, despite being told that it won't work: That's hard for me to understand.

...the 35mm( batten depth) cavity which I was initially going to fill with Anticon medium 75mm, this will easily compress & fill the 35mm gap

:shock: :!: Which would make matters even worse! If you tightly compress insulation into the air cavity in a wall, then it bridges the gap acoustically, which REDUCES isolation, instead of increasing it. Yes you DO need insulation in the cavity: it is an important part of the system. But you CANNOT compress it. In fact, did you even read the literature that you linked to? The manufacturer himself clearly states, not once but twice in that brochure, that "material performance is a function of thickness - always ensure that the insulation can recover to its stated thickness by using Bradford Spacer Systems": In other words, if you compress it, not only will it bridge the cavity acoustically, it won't even isolate thermally! It just will not work. You cannot take building materials and misuse them in ways they were never intended, ways that even the manufacturer specifically warns against. I would seriously, seriously suggest that you should re-think this whole plan, and just build the studio in the garden somewhere. I can't see any way that you can make that space usable, unless you are prepared to spend a huge amount of money on doing it right. Moving forward with your current plan is going to lead to major disappointment, and perhaps even a structurally unsafe situation. Are you aware that your homeowners insurance will very likely NOT cover anything at all if your house collapses due to unsafe modifications, such as the ones you are planning? - Stuart -

Hi Stuart, Thanks very much for your patience in explaining everything thoroughly. I knew it would a tall order. Wow.... I'm pretty depressed about it all now. :cry: I'll take a couple of days to digest your insights. Again, thanks for sharing. All the Best Matt

cLoudBase wrote:

Yes well..thanks for the analogy .. emphasis on anal :lol:

It is my strong suit. We do not stay here handing out flowers and pats on the back for poor decisions or lack of education. We EXPECT the posters to either have some "want to" which leds to getting that education OR spend the money and have the decisions made for them from a design professional. In any event, you keep saying "structural limitations" as if you have a handle on this. I am not buying it. What I think is going on is that you are involved with something that you do not know how to work with and you are getting BAD information from your friends. It is very common, very, for Stuart or myself to tell folks to STOP the project until you have a better understanding of what it is you are up against. You are using GreenGlue in ways the manufacture has not tested so there is no proven results data, that is just one of many areas that you keep trying to put this square peg into a round hole. If you do not know what you are doing...say that, we can help you. What we CANNOT help is a prideful person who refuses to admit they are lost in the dual world of construction/acoustics. I may be rough around the edges friend, but if you need someone with 37 +/- years of experience in exactly what you are doing, you are talking to him.