Yet another question to clarify 2, 3, etc leaf walls

I am building a studio in a large steel shed, 12 metres x 8 metres x 3.6 metres. First I intend to put a layer of SoundScreen mineral batts against the inside of the steel walls (there is already a layer of sisalation thermal insulation) then cover these with plasterboard. My plan was then to build a second wall about 100 millimetres inside the first, with a timber frame, and plasterboard on both sides, filled once again with SoundScreen. HOWEVER............. after spending hours reading the various threads on the subject of 2 leaf, 3 leaf, multiple leaf walls, I'm still not sure whether what I am building is 2 leaf, 3 leaf or multiple leaf and whether it is the best method to use. The only alternative I have thought of is to leave off the plasterboard from the inner side of the second wall, the side closest to the outside wall, and use plastic sheeting (the stuff that the SoundScreen is wrapped in) to hold the SoundScreen in place inside the timber frame. Is either of these better than the other? Are both rubbish? Is there a third, better, method I haven't even thought of? Regarding the ceiling: I am using a similar method to the walls, except that in the middle of the peak of the roof I will be putting in a frame and having the centre 2.4 metres of the ceiling flat, the outer sides will slope with the roof profile. And I haven't even started working out the construction of the inner walls between the control room, drum room, vocal booth or studio yet............. Any help and all constructive suggestions are appreciated in advance.

"First I intend to put a layer of SoundScreen mineral batts against the inside of the steel walls (there is already a layer of sisalation thermal insulation) then cover these with plasterboard. My plan was then to build a second wall about 100 millimetres inside the first, with a timber frame, and plasterboard on both sides, " This is more like a two leaf...except that what you are suggesting is basically a coupled assembly X2. Much like an interior wall in your house with hard boundaries on either side but both connected to the same frame. Then you add another of the same type of wall assembly. This type of assembly has had much attention, and has been proven to be less effective, costs more, and hurts your low frequency transmission loss.

Thanks for your speedy reply.

This type of assembly has had much attention, and has been proven to be less effective, costs more, and hurts your low frequency transmission loss.

So what would you suggest as an alternative in my situation?

stosostu wrote:

Thanks for your speedy reply.

This type of assembly has had much attention, and has been proven to be less effective, costs more, and hurts your low frequency transmission loss.

So what would you suggest as an alternative in my situation?

I would suggest getting something uploaded so we can see first hand what it is we are talking about...a down and dirty sketchup or even hand drawn would help to get the environment across more clearly.

I have attached a file with a drawing of the wall construction. I don't know how to actually put a drawing into a post. Basically my outer wall will be: outside world > steel V crimp > Sisalation foil > steel framework filled with Soundscreen batts > platerboard then an airgap of 100mm then the second wall, not connected to the first, which will be plaster board or plastic sheet (depending on the advise I get) > timber framework filled with Soundscreen > plasterboard. Given that the steel framed shed is already there and cannot be changed, is there a better way of soundproofing the outer walls?

A metal shed is going to be difficult to isolate from sound. I assume there is no venting in this building, gable or ridge vents...any path that air can move around in is that correct? I wouldn't say for certain, not knowing this metal shed personally (pictures would be a great benefit) but I do not know if attaching a hard boundary to the interior side of the structure is a good thing or not based on so many unknowns at this point. Still, what you are trying to develop is a mass/air/mass type assembly. This is a hard mass boundary attached to a frame then an enclosed air space/spring/ and another frame with a hard mass boundary attached. Anything else is just more cost, more work and less isolation than most might think. A typical setup would be to install mass to the backside of the exterior framing boundary, this would be your exterior mass. Then you would give as much air space as possible. Then you frame up a new set of walls that will have a hard boundary attached to the interior side. That would be the final "mass" in your mass/spring/mass. If you did frame the interior with metal studs...how do you suppose you will get them to remain vertical with no attachment to the exterior structure? Is your plan to construct a ceiling in this new room from metal? Are you a talented diy kind of guy or will this be built for you? Lot of things to consider...electrical, air con...and keeping this structure air-tight, these are a few of the challenges you face.

Thanks again for your help with this. To answer your questions: There are no openings or vents in the building, not even windows, it just has a double door at one end. The interior walls will be built on timber, not metal, frames and will be self supporting as they will form the inner rooms, as you may be able to see from the attached sketchup. The ceiling will be built in a similar way to the walls. There is a steel framework with steel outer covering and sisalation on the inside. Once again I have filled the space with Soundscreen and covered that with plasterboard. Below this, with a gap of 100 mm, will be a timber frame, not attached to the outer wall, but supported from the inner room walls. This will have plasterboard at the bottom, facing into the room, then Soundscreen between the framework. Electrical wirring has already been installed into the shed, though not connected, by my electrician (fortunately he's a guitar player, so he did it for 'studio time' in the future). I have a ducted AC system which will be installed outside the shed on a seperate stand and then the ducting fed in between the two wall layers. It has three seperate duct outlets, so one for the main room, one for the drum room and one for the vocal booth. The control room will have it's own split system. Each of the inner rooms, DR, CR, VB will be completely free standing and there will be an air gap between the walls of each room and the next. Timber framed walls with Soundscreen. I don't know about talented, but I am a DIYer and I have built additional rooms on my house, and lots of other building projects quite successfully. I will certainly be doing all of this myself.

Here's a photo of the walls during construction.And some of the partially finishe walls and ceiling for the first 'layer'.

Another view of the proposed wall structure:

The silence is deafening, I hope my studio is ths quiet.............. :D

Ahhh that nice clean newly built shed brings back memories. Your lined shed and double sided timber frame is a 3 leaf system some may even say it's a 4 leaf. If you have your heart set on hard plasterboard walls in the interior of the studio then take the plasterboard from the other frame and put it on the internal walls with or without green Glue. Making the 16mm wall a 32mm wall But, with experience I would recommend doing the studio "inside out" as per john's plans. Hang the 2 layers of plaster on the outer edge of the frame. (with or withour green glue) In the later method you don't have to worry about adding a bunch of absorption and huge amounts of bass traps. What you do is add reflection back into the room ie timbers slats. Or do a mix of both? Inside out Control rrom and vocal booth and plasterboard/live drum and live room. lil

Thanks for the reply Lil, though I'm not sure what you mean by inside out. Do you meean putting two layers of plasterboard on the outside of the timber frame then leaving the Soundscreen exposed into the studio? I'll have a look at John's design to see if I can see what you mean. Bob

OK, I read John's design, is this what you mean by 'inside out' wall construction? I don't really want the bare Sounscreen as the inside walls of my studio and I'll need something solid to mount power points, XLR connector boxes, etc on. What do you use?

you frame out as needed for the support of boxes, lights, etc. plus you can use slats for absorption as well as plastic and cloth over the insulation.

Excellent, now we're getting somewhere. I guess this means I have to remove the gyprock that I have installed so far. That must be a lesson, ask before you start................duh. At this stage then I propose to have the first layer of walls as steel panels and steel frame with Soundscreen batts held in by blue battens, as you can see in one of the photos above. Then an air gap of 100mm and a second wall that has gyprock, green glue, gyprock, timber frame filled with Soundscreen. Then for the actual interior wall surface I will have: In the control room, slats on the front and rear walls and cloth on the side walls, In the vocal booth, gyprock on two adjacent sides and cloth on the other two, In the drum room, all walls gyprock, and in the main studio, gyprock with absorbers etc. The equipment room and officwe will be gyprock. How does that sound? (metaphorically). Each of the walls that adjoin another room will be double walls.

Have you built the timber frame yet? What plasterboard are you going to remove?

No I haven't built the timber frame yet, though I do have some of the timber. I was going to remove all of the gyprock that I have put on the walls and ceiling so that the first layer of Soundscreen is exposed, merely held in place by the blue steel battens. My next move after that would be to fit the first layer of Soundscreen inside the roof, held there with blue steel battens, the same as the walls in the earlier photos. Then I'll build the timber inner wall frames.

Hmm, seems like alot of work removing the plasterboard. But if thats what you think.

Bob - don't treat the outer steel as a leaf as it's not airtight and really offers no sound isolation. Your plaster layer should be treated as your outer skin, seal it totally all round including the ceiling - then build the inner walls inside out with pink batts type insulation or dacron rolls on the back. No green glue is required. Have a look at these finished studios to get an idea of how to use timber and cloth. http://johnlsayers.com and check this thread for inside out construction viewtopic.php?f=11&t=6968 cheers john

Thanks for your input John, I was getting rather confused. What you suggest is what I had intended originally, except the inside out walls, I didn't know about them at the time. So, my intention now is to continue to gyprock the outer walls and ceiling, over the layer of Soundscreen. Then I'll seal that layer with caulk. Do you suggest caulking at the joint where the walls meet the concrete floor? Then I will build each of the inner rooms as a free standing frame, with gyprock on the outside (one or two layers?) and use the 'inside out' method with Soundscreen and cloth. Is there a particular type of cloth that is used on the inner side of these walls? I intend to put slats of various kinds in these rooms, except for the main live room, where I was intending to use perforated gyprock, http://www.gyprock.com.au/our-products/ ... board.aspx, and the drum room, where I intended to use plain gyprock to get a more 'live' room. Do you think this will be OK? It was also my intention to use the existing concrete floor, probably covered with timber floating floor material, in all the room except the control room and the drum room. The CR and DR, are to have raised floors, 70 x 35 timber sitting on rubber with 32 mm chipboard/MDF covered with timber floating floor boards. Does this sound right? Lil_envy, I just read through your build diary twice and it is inspirational, I'll certainly be using it, along with other threads, as a guide for my construction. Maybe I should change the title of this thread and use it as the beginning of my own build diary?

You need to get some ventilation into this building and you do not need to construct a light-weight floor that is of lessor weight with lessor damping than a concrete floor.

Ventilation will be by ducted AC and ducted extraction, both with baffle boxes. The raised floor in the CR is purely to accomodate cable looms and in the DR it is a riser so the drummer can be seen.

I was thinking more about the building, not people :)