Piano room over slab

OK. Here's one for ya. I'm building a studio to record my piano, because I'm tired of waiting until 2 in the morning to record in the old church it currently inhabits. The slab under the piano room is 20 inches thick over sand and gravel. It's isolated from the rest of the studio. There is radiant heat in the slab. From my research (and admittedly there's always more I can find and learn...) I think I'm OK not to raise the floor and just use a layer of polyethylene barrier plus a sixteenth inch of foam, plus sub floor, plus engineered wood flooring (seems to be best for radiant heat). Any comments on that?\ Now...the manufacturer of the wood flooring says that there's no problem with putting a piano on the stuff. The piano won't be moved much, if at all. I'm also wondering if I should float the floor under the piano just to be on the safe side, or is that overkill, considering the thickness of the slab and its isolation? Thanks.

TWENTY INCHES! What was it, a bank vault? Since the floor is radiant heat, I would go with not floating the floor because as you said it is so thick (!) and isolated from the rest of the structire. I always thought that a going-out of business bank's vault would make the ultimate iso room.

Naw...the concrete just had to come up to the level of a house. We do have a bank vault in our office...and yes, that's where we store the "tapes". A piano won't fit in there, however. Might be good for fiddle and accordion. (OK now...no jokes.)

Aaberg wrote:

Naw...the concrete just had to come up to the level of a house.

So they did it by pouring twenty inches of solid concrete? That's just SO absurd.

Got another way? the slab is 20 inches at the edge, so the concrete goes all the way to the ground. Kind of like your legs, you dig? Unless you're floating on air. The middle of the slab has an elevated rise of sand and gravel, so in the middle, the slab is less thick. This slab ties together 2 houses, kind of an architectural deal, gnome sane?

Aaberg wrote:

Got another way? the slab is 20 inches at the edge, so the concrete goes all the way to the ground. Kind of like your legs, you dig? Unless you're floating on air. The middle of the slab has an elevated rise of sand and gravel, so in the middle, the slab is less thick. This slab ties together 2 houses, kind of an architectural deal, gnome sane?

Of course, that is a thickened edge slab-on-grade foundation, but that is WAY different than a 20 inch slab, which is what he said.

Sorry about the lack of clarity...any suggestions from anyone else re: my original question?

"The slab under the piano room is 20 inches thick over sand and gravel. It's isolated from the rest of the studio." - Meaning that there is no hard connection between this slab and the rest of your construction? If so, what about wall framing, ceiling/roof framing, etc - any hard contact there between areas? Innovations pretty much covered it as far as floated floors over radiant heat - not a good plan. If your slab is already isolated, you could just do either RC/drywall over studs and under ceiling joists, or full double wall construction - maybe a sketch or pic of what's there would help us help you... Steve

Thanks, Steve. I'm pretty much set with what I have to work with for walls. Will send picture...I'm pretty sure this is the only recording studio in the world with this construction, but who knows? My main concern now is with the floor of the room. In fact, this leads me to a thought I had this morning. Most of these posts don't stick to one topic, but relate to one PROJECT. That's very good for the builder of the one PROJECT, but it makes it very convoluted to try and look up info on one TOPIC, i.e. Floors. I can see the advantages of both ways, but I'm trying to just post something different for each topic in my building. Would you prefer that I just post once and get all answers on that "Subject" heading? Is that clear? Thanks.

Yeah, so far it seems to me that the "project" approach works better for the "projectee" - for other members, if you're looking for specific topics the search engine can help. I'm working on a real FAQ type section which will probably not happen for several months, since it's summer and I only have 4 major and about 15 minor projects I need to start/finish before bad weather sets in again. It was suggested recently that I gather the "stickies" into a single heading so they wouldn't take up so much room on the first page - I'd been thinking about doing that, although I'm still not sure it's a good idea - already, new members come in asking questions to which the answers are already available, so I'm not sure hiding the "stickies" would be a good thing. Maybe I'll start a poll on ways of improving accessibility of the info that's already here - the amount of time I've already put into this would have bought me a new Yamaha DM-2000 if I'd spent the time at my job on extra projects... Steve

Steve, I can't begin to tell you how much this forum and your input has helped me. Very solid stuff...any difficulty finding stuff is minor compared to the service we get. Just wondered if you had a preference for how we submit messages, and even thought that if you decide on a "best" way, you might use that as an introduction to the site. Sincerely, Phil

Cool - I've been toying with the idea of an online "form" - one with all the blanks people typically forget to fill in when first posting - I think that would save a lot of "back and forth" - not sure how to make it generic enough to apply to the majority of members' questions, though... Steve

Yeah, I guess you could list the most-posted topics (insulation, floors, wall, gypsum, )...it'd take some thought, huh? Thanks for the great work...we really appreciate it. I'm still searching for someone who's insulated a curved wall. Found a farmer in Kansas who's built an office out of a grain bin and his builder has some ideas, but not to the sound-insulating specs we're hoping to get. I can figure out how to get the insulated wall/air space/insulated wall right, but can't figure out how to seal the 703 on the second wall. Will continue this on a Subject called "curved walls/ceilings".

703 doesn't need to be sealed at all, just inserted snugly between studs. For outer wall mass, if this bin is steel, what about a 1" layer of stucco on the inside, then steel studs (25 gauge, and don't try to support the ceiling on these - they need to be light, because you can't get RC to go around a curve and still work for decoupling), fill with insulation (2-3 PCF ideally), then go to a drywall supply house (home depot doesn't count) and ask for 1/4" drywall (yes, it does exist) and do 4-5 layers of that over your steel studs? IF you support the two ends of the stuff for a couple days (without supporting the middle) you can pre-bow it to close to the arc you need for a circular wall - then, (carefully, the stuff is fairly delicate) screw each successive layer to the studs, starting each course offset vertically and horizontally from the last - for every other course, you'll want half-width sheets - cut these first, and THEN pre-bow them. This is used in some houses for curved partitions - for sound, you just need more than the normal two layers of 1/4" to get the extra mass. Check locally for Myron Furguson's book, "DRYWALL" (catch title, hun?) Or order it from Amazon. I found mine at Home Depot, yours may or may not carry it. The book shows a lot of drywall pix, including this laminating curved wall stuff... Steve

Steve, Thanks a million for the research. I spent all day Tuesday reading all the posts in the forum...most time I've spent on a computer since the last piece I orchestrated. My eyes hurt! But there's an incredible amount of great info here. So, the upshot is that we decided to stay away from curves and completely float the interior walls! We did it! Finished the framing today. No parallel sufaces, no 90 degree angles. It's some pretty complex geometry, but looks right and is really striking. Will send pictures and may even get around to a drawing. Every wall is floating on a half inch of EPDM that we got dirt cheap from a local roofer, then cut with small metal shears into pieces that fit under 2X6. It took 8 layers to do, but sure a lot cheaper than buying the pucks. None of the walls touch the bin. The peak is 18 feet high and the lowest line is a bit under 16. Didn't lose much floor space at all because of the way we cut into the bin with the SIPs. The bin is covered with an inch of urethane foam for weather seal and rigidity, then one and a half inches of cellulose insulation. Supposedly gives 51 STC, but I doubt it. There is a minimum of 8 inches of air space between the insulated bin and the dry wall, sometimes as much as 12, and actually 3 feet between the roof of the bin and the interior roof. I'm going to put R38 fiberglass between the interior roof and bin roof because it's easy to do and seems right. My question is, what should I use to insulate the air space in the walls and how should I apply it? Thanks for all the help. Phil

Hello Phil, I've got a couple of questions for you. What did you use or do to keep your floating walls from moving? I mean, did you attatch the rubber to the walls or floor with adhesive or something? And what about cieling joists. Are they resting on these walls, or suspended from above? Thanks fitZ

fitZ, Perhaps, "completely floating" is misleading, because we put in a few nails to hold the frames in place while we worked. . I don't think they'll conduct much sound. No problem with the chunks of EPDM moving, or the walls slipping off, probably because the framed wall segments were pretty small, being sides of a complex geometric structure, and we got scrap EPDM cheap, so made half-inch thick bricks , about 5" X 8" that were level and fit the boards. To give you some sense of it until I get pictures, one segment of wall had 4 smaller segments about 4 feet wide that angled away at about 6 degrees. We framed them one at a time and put them on top of the EPDM. It was pretty tediuos. There were 3 of us working, and there was a lot of temporary bracing until we got the "somewhat round" structure stabilized, then we took away the braces and the whole thing, including ceiling, stood by itself!! The other two guys could hang from the joists with little movement of the frame. I then caulked all around the bottom with Silicone II. It was very solid, and since I'm thinking I only need one layer of sheet rock with all the insulation and the insulated bin, I'm not at all worried about the strength (even if I need more.) I'm pretty psyched. Most of the frame is built of 2X6's, so it wasn't cheap, but I couldn't think of a better way to do it.

fitZ, Sorry, I got carried away answering the first part of your question. The ceilling joists are attached to the walls, but still don't come into contact with the bin. Picture a completely framed room, resting on EPDM bricks, built inside a grain bin. The hard part to picture is that only a third of the bin reaches all the way to the slab, and the rest is cut in by SIPs, on which the rest of the frame rests (once again floating on EPDM bricks.) Best wishes, Phil

Thanks Phil, sounds really unique. Post some pics as soon as you can, and best of luck with the room. fitZ

2 things today. I'd like to post some pictures, but I've got one of those old-fashioned "analog" cameras, so I send my film to ofoto and then post it on their site. I can't figure out how to get those pictures over here, since it takes an individual email address to access the site. ??? Second, Mr. Fly said, "703 doesn't need to be sealed at all, just inserted snugly between studs." Just thinking...why not install the 703 as a solid wall, not between the studs, but on the inside (air space side) of the studs? Wouldn't that stop a lot of sound from hitting the studs and thus, reverberating?

Phil, if you can access the pix you might be able to right-click on the pic, choose "save as" to your hard drive, then if necessary resize the jpg down to less than 800 pixels wide, rename and post them here using the Browse button below the text box when posting. For multiple pix, after doing the browse thing click "add attachment", and do the whole thing again. Not sure what the limit is, I think at least 4 pix per post. Meantime, if you're on a PC could you do a basic sketch in Paint or something as to where you want to put the 703? This stuff isn't actually RIGID, so it needs support from SOMEWHERE... Steve

Steve, Thanks. I did a small paint drawing of a cross section of the proposed bin/piano room wall. Don't know if it's any clearer than words. Let me try again: Normally, batting or 703 is cut to shape and inserted BETWEEN studs, right? I wonder if better results might be achieved by just taking whole sheets of 703 and gluing them to the studs, leaving an air space between the 703 and the sheetrock ( yeah, I know, 3 leaf, bad...but 703 really isn't a leaf, is it?). That way, whatever sound is getting past the bin wall and the foam would hit a solid layer of 703 with no wood to resonate with. Clearer?

Front view of bin. You can see how the SIPs are cut in. In the back, the bin goes all the way to the slab.

Sorry to jam so many of these in without a reply, but I go on the road this weekend, and just wanted to get these pictures on while I sort of know what I'm doing! This is a scan of a reduction of a blueprint, edited with Paint, so it's fairly pathetic, but maybe gives you an idea of what's in my back yard. Best, Phil

OK, finally got what you were asking - basically, the flaw in that thinking is that you WANT the 703 to at least slightly touch your inner wallboard, so that it dampens any vibes in the wallboard (which will be worse than any minor vibes in the frame, since it's a larger membrane and any vibes will radiate into the room... If you can, it wouldn't hurt to ALSO put some normal fiberglass house insulation in the cavity BETWEEN the 703 and the outer layers, it should improve TL by maybe 2-3 dB... Steve