Weird Ceiling Issue - Any Ideas?

I posted a thread that included this around a week ago and though it's had quite a few views, as no one yet has responded, I thought I'd stick some pics up to make it a bit easier to figure. I'll recap ...... I'm about to take on the ground floor of a 3 story brick built industrial building and my plan is to put 4 rehearsal rooms and a recording studio in it. (See Floor Plan below) The existing ceiling height is approximately 14'. The rehearsal rooms would be 18' long x 15' wide x 10' high. (3 layers of Gypsum Board on the walls fixed to a stud frame - 2 layers of Gypsum on the ceiling with a layer of Green Glue between them - medium density Rockwool Slab Insulation all round behind the Gypsum). There are a few things that have been bugging me though, and I'd be grateful for a little input if anyone here fancies giving me the benefit of their knowledge. Having read a bit on this forum and Rod's book regarding the merits of timber floating floors, my first quandry is whether or not this is worth doing. (The existing floor is a poured concrete slab.) I'm considering 2 methods of building the rooms. ( See Diagrams Below) Version 1 This would be to build the stud frames directly on top of the existing floor, and Version 2 To build a 4" x 2" floor that would sit on neoprene U-Boats and put the stud for the rest of the room on top of that. I'm thinking to fill the floor void with Rockwool Insulation. In addition to the floor question, I'm also not sure about what to do with the gap between the top of the new ceilings and the underside of the existing ceiling. Bearing in mind that it will be between 3' 6" and 4', will this be good for isolation between the rooms and the 1st floor or will I get any weird resonances? I'm not entirely sure what the existing ceiling is made of, but it looks like the usual skimmed gypsum board attached to the rafters. If it is this, should I rip out the boards and and fill the gaps between the joists with gypsum and insulation or will the fact that there is such a large air gap between the new ceilings and the existing ceiling make this unneccesary. (It's quite a large space to cover, so the additional expense of having to do this doesn't exactly fill me with joy). The idea is to post our progress up on this board as the project goes along, though it would be helpful, to say the least, to read peoples ideas on what I've mentioned here before we make any potentially disasterous mistakes at the outset. Cheers all!

it's funny that you say you've read rod's book and posts on this forum about the merits of floating a wood frame. it's funny because you say you're still considering it. my advice for the floor would be to build the deck directly on the concrete, not on the auralex uboats. otherwise much hard math and lots of concrete would be needed

i'm not as sure about your ceiling question, but my inclination is that even with a four foot air space you would still have a 3 leaf problem, maybe best to remove the existing first leaf of the ceiling. just a guess though

Thanks for the quick reply Johnz. Well yes, it is now looking like I'm going to be building directly on top of the existing concrete floor. I've been involved in a few previous builds with other people where the timber frame thing has been the way it's gone and it's only been fairly recently since I've been reading the stuff on here that suggests it's not the way to go. I only found this site a couple of weeks ago and was so impressed with the wealth of info and ideas that I got a copy of Rod's book last week. (You'll have to forgive me for being a little shocked to find out that the methods used previously were in all probability not the best, shall we say). With regards to the ceiling bit, yes I understand that with the way it is at the moment, there is a 3 leaf issue. Assuming that I do remove the first leaf from the existing ceiling, would you suggest then that I place gypsum board in between the rafters and insulate below that as well? (I guess with the money saved from not floating the floors, this then becomes a little more viable financially). Any opinions, ideas, suggestions or comments on the rest of the plan? Thanks again.

With regards to the ceiling bit, yes I understand that with the way it is at the moment, there is a 3 leaf issue. Assuming that I do remove the first leaf from the existing ceiling, would you suggest then that I place gypsum board in between the rafters and insulate below that as well

The idea is to have only two mass with a sealed air space in between. If the building ceiling is already massive (wich i doubt) then you won't need to do what you describe, otherwise that may be an option. Don't forget this is all depending on the amount of isolation you need. Remember that small rooms are more difficult to deal with acoustically, so having great isolation at the expense of bad sounding room is something that needs to be tought about. :wink: 2X4 for your ceiling joist are a no-go. This all depends on the span you need, if you have really wide rooms then you may end up with 2X8 or even 2X10. Look for the span calculator in the reference section. Please don't assume that it will hold the weight.... :? I agree with johz don't float you room(s). eventough i have float mine :( Also since you have access to that height, i'd strongly go for a 12' ceiling for you rooms. 12' finished inner leaf ceiling that is.

Cheers Eric, Well, after having felt well and truly castigated for the mention of floating the floors, and after reading up on it for the past couple of weeks, I've decided to go with building the walls directly on top of the existing concrete slab. I'm also inclined to think that removing the boards from the existing ceiling to prevent the 3 leaf effect would be a sensible idea. (I'm hoping that I might be able to remove them carefully enough to be able to re-use them between the rafters).

The idea is to have only two mass with a sealed air space in between. If the building ceiling is already massive (wich i doubt) then you won't need to do what you describe, otherwise that may be an option. Don't forget this is all depending on the amount of isolation you need. Remember that small rooms are more difficult to deal with acoustically, so having great isolation at the expense of bad sounding room is something that needs to be tought about.

Yep. I hear what you're saying. Though bearing in mind there's the distinct possibility of the rooms occasionally being used by "metal monsters", I'd say that isolation is the key thing I'm shooting for to begin with. I have a budget of around £3500 all in, per room, including aircon but not labour, and I'm (probably naively) hoping the rooms can be put together leaving enough spare dough to then spend a little on tuning them. (One suggestion I did quite like the sound of, was the stacked, dense insulation, bass trap triangles in the corners with the slotted frame idea. I'd be interested to hear what people's experiences have been with those).

2X4 for your ceiling joist are a no-go.

I've been scrabbling around for the past couple of nights and I can't seem to find the span calculator anywhere. (Maybe I'm just being really dumb, but I've done various searches and can't find anything. I'll keep looking though. For the time being, in order to not take any chances, I've adjusted the plan to include 8" x 2" ceiling joists. (though I have seen people use 4" x 2" and 6" x 2" in similar sized rooms before). The joists will run across the 15' span.

Also since you have access to that height, i'd strongly go for a 12' ceiling for you rooms.

I was planning on the rooms being 18' x 15' x 10' high. No specific reason for the height, other than wanting to mount the lighting on lightweight frames from the ceiling, (with possibly some absorbtion up there too), so the buggers can't get to the lights and break 'em whilst trying to adjust them, (like they did the wall mounted ones in my current place). 12' high ceilings though? Wow! A fair few more boards and timber (and cost) there. Would this be for a better room size ratio? Better distribution of modes? I guess it would mean less board cutting at least. Would the decrease in airgap between the top of the rooms and the existing ceiling make any appreciable difference? Although I want the rooms to sound nice to play in, I also have to consider the constraints of budget, and despite the fact that the rooms are being built in an industrial unit, and I won't at least have to get the noise levels down as much as if I was below mum, dad and 2 kids trying to watch tv, I do want to do as much as I can not to upset anyone. Bearing in mind the not inconsiderable amount of money I will be putting into the place, I want to be as confident as I can be that any noise created there will not be an issue for anyone else. I guess the plans I've been discussing here so far are more to do with the rehearsal rooms side of things, as I think in terms of sound leakage, they will cause the most problems. (They will also be the 1st rooms to be built). I'm anticipating using some more interesting ideas for when it comes to the recording studio, some of which would be the use of higher ceilings and more irregular shapes in the room designs. I've posted the Version 3 room plan below, so I guess the two original ideas in my first post can be disregarded now. One other thing that's still bugging me though, is what to put in the cavities between the rooms. Dense insulation against the back of the boards of one room with more lightweight stuff between that and the dense insulation that would be against the boards of the next room? Lightweight insulation all the way to simply act as a damper? What about above the ceilings? Surely it wouldn't be practical (or affordable) to fill the whole airspace with insulation? What gives here? Questions, questions. :?:

Hi pete Here's the link for the span calculator : http://www.awc.org/calculators/span/cal ... cstyle.asp 15' span would definetely need 2X8 @ 16" OC.

Would this be for a better room size ratio?

Well, that depends on the width and depth of the whole room of course.

Better distribution of modes?

Defenitely. You may also slant the ceiling in the CR (if CR there is )from front to back. in a 12 degres angle. If i had that ceiling space this what i would do in a snap. If these rooms are for band rehersal only then 10' is OK IMHO. 4' feet as an air gap is a huge "spring" although i'm sure it'll be efficient, i just can't tell you what you'll be loosing by reducing it to 2', probaly some very low end stuff. But keep in mind that whatever you build it won't be totally soundproof in the whole spectrum anyway. Metal Monsters will probably be a problem Is the concrete floor in a basement, on a second floor ?, please give us more info as to where this will all be built. In any case,did you made sure if the floor can carry additional dead loads, and if it can, how much more. This is really important for safety reason. Don't assume that a concrete floor will handle anything. Same is true for the building ceiling make sure that you can add dead load to it, and if you can how much, get a figure. As for insulation, in you case i would go for rockwooll in the cavities slightly press against the board. same for the ceiling. Now as for thickness i am not sure for your situation, 3" for surE but may be 6". Knightfly or Sharward may know more about that. Complete fill the whole 4' air gap of the ceiling would be a waste of money IMHO.

Pete, in all the well-meaning advice you've gotten so far, we still don't know a few CRITICAL things - Since this is a rehearsal space, how LOUD will your customers be - and how TOLERANT of the band next door will they be - will they be recording, or just rehearsing? What's your budget? What's the noise situation around your building - and what hours of operations are you contemplating? Your answers may well change EVERYTHING that's been suggested so far - this is the reason for the "don't even think about...." sticky at the top of the forum - we don't want to waste either your time or ours. Depending on your answers, floated rooms may be absolutely necessary or they may be un-affordable. We'll know more when you answer the above... Steve