Stuck with sand and floating floor - what's the best way

Hey guys, I've been following these principles for years. I've got Rod's book. I have 90% of the concepts down and here's what I'm doing: Building a small iso booth. It is on a 3" fir deck with exposed (open) floor joists underneath (which I will probably beef up with drywall as Rod suggests later) For the build I'm using the standard- double drywall (sandwiched GG), 2" airgap to next wall, double drywall (sandwiched GG) (You know the standard double leaf deal with rockwall in each wall) So for the floor I'm thinking of using 2 X 4's on flat with GG on bottowm and top. Then, pour sand and fill the whole cavity betwwen the 2 X 4's, then put drywall, and 3/4 ply on top of that, before horsehair underlay and carpet. Any suggestions as to how to best decouple the first 2 X 4's on flat from flanking best? Is my GG idea on top and bottom of flat 2 X 4's good or would strips of rubber or similar work better? I know floating sand floors would not be "recommended" by the average person here, but based on what I've provided, any ideas? It is an iso booth being built on an isolated island so the only noise I'm trying to keep out is the drummer downstairs and not trains or the city. Please don't suggest concrete slab as I've already decided against if for multiple reasons (including weight and aesthetics of changing building underneath) Thanks for any insight on the floor, Best, -Christian

Hell man, if I can't recommend concrete...I am lost! I prefer if you not let me know where you are in the world or how big this booth is either...I LOVE guessing games !!!!:) OK, I'm thinking somewhere in Idaho...the structure is...let's see 4 feet wide by 4 feet deep. Close? Too far North? Square base not working for ya?

Hi Christian, and welcome! There is an announcement at the top of the forum about what to do to assure getting as many responses as possible. The announcement leads to this post (click here). Actually, several people, who are experts on this forum, will not reply if you don't do what is written in that post. Many others who are very helpful, will not reply out of respect for the moderators' wishes.

For the build I'm using the standard- double drywall (sandwiched GG), 2" airgap to next wall, double drywall (sandwiched GG) (You know the standard double leaf deal with rockwall in each wall)

That's a good start! Regarding floating floors, you might already have looked here, but maybe you should look again viewtopic.php?f=2&t=8173

thebarn wrote:

... on a 3" fir deck with exposed (open) floor joists underneath (which I will probably beef up with drywall as Rod suggests later) ... I'm thinking of using 2 X 4's on flat with GG on bottowm and top. Then, pour sand and fill the whole cavity betwwen the 2 X 4's, then put drywall, and 3/4 ply on top of that, before horsehair underlay and carpet.

I don't get the idea of using GG on the frame. What will that do? It's not caulk, and it's not glue, and it's not meant to be a sealant nor a decoupling membrane.

Is my GG idea on top and bottom of flat 2 X 4's good or would strips of rubber or similar work better?

well, if you want to float your entire room here is what is ahead of you: You need to calculate, in advance, the final total weight of your entire room, including all the walls, floor, ceiling, equipment, people, HVAC, etc. Everything. Then you need to figure out exactly how that will be spread around on your 2x4 frame. So for every square centimeter of that frame, you need to know exactly how much weight will be pressing on it. Then you need to do some research and find some material that will compress to exactly the right amount so that it acts as a spring, when it has exactly the loading on it that you figured out above. Obviously, the loading under doors and windows will be higher than under the walls, and the loading under the empty floor space will be lower than both. But it will be different under each part, so you will need different materials under each part, that are just right to support the load for that particular section. You MUST do these calculations precisely, with no errors. If you get it wrong at any point, then there are two possibilities: 1) There will be too much mass over that point, it will over-compress the material, which will bottom out, and your floor will flank: So you just wasted an awful lot of time and money. 2) There will not be enough mass over that point, so the material wont be compressed enough to act as a spring, and your floor will flank: So you just wasted an awful lot of time and money. If you think you can just guess, and throw in any old bit of rubber, neoprene or EPDM that you happen to find, then don't bother: you would be wasting your time and money. The chances of you lucking out and getting your entire floor to float are about the same as your chances of winning all the lotteries in all of the states that run them, on the same day. Remember, if your floor flanks at even one single point, then that's it. End of story. Game over. Wasted effort. You have to get all your calculations right for every single point of your floor, or else it WILL flank.

I know floating sand floors would not be "recommended" by the average person here, but based on what I've provided, any ideas?

My idea would be to not try to do it yourself. Hire an experienced studio builder who has done it several times before, and done it successfully every time!

It is an iso booth being built on an isolated island so the only noise I'm trying to keep out is the drummer downstairs and not trains or the city.

A drummer is even worse than the city!! The drummer downstairs is probably producing 115 dBC. There is no way on this planet that normal city noises get anywhere near that. Perhaps 80 or even 90 in a really, really noisy place, but that's still nearly one hundred times less energy... Drums are the hardest things of all to stop, since most of the energy is in the low frequency end of the spectrum.

Please don't suggest concrete slab as I've already decided against if for multiple reasons (including weight and aesthetics of changing building underneath)

So you DON'T want to do a slab because of the weight, and instead you want to do a couple of layers of 5/8 drywall, a couple of inches of sand, another layer or two of drywall, a layer of 3/4 plywood, then underlay and carpet? So what's the difference? That sounds like about the same weight as a slab anyway! At least, if not more! Drywall is already half the density of concrete, sand is even more dense than that, plywood is not light, plus framing, carpet, etc.... you probably have enough mass there already for a three inch slab, or something close to that! Wouldn't it be easier to just do the slab? Either way, did you do the math on the floor? Can it take the kind of extra mass you are talking about? That sand-filled floor with drywall, plywood, drywall and carpet is already very heavy, then you want to build walls with four layers of drywal on top of it, plus a ceiling with another four layers, plus the framing, etc.... What did your structural engineer say when you checked with him about loading your floor like that? You did check with a structural engineer, right?

It is on a 3" fir deck ...

I dunno, and I'm not a structural engineer, but it sounds kind of "iffy" that a simple 3 inch fir deck could take a couple of tons of extra weight without collapsing... - Stuart -

Hey guys, OK I get it I just read what I was supposed to read before posting (Sorry, got that backwards) I'm an open book: Saltspring Island, BC Canada (Right between Vancouver and Vancouver Island on the West Coast) Beautiful dead quiet, tranquil piece of land with no outside noise affecting inside the building (other than rain sometimes which I like bleeding into the mic actually!) The iso booth is not meant to have PERFECT isolation from sources 20 and 50 ft away so maybe people don't even want me here. I understand the lengths that one can go to do it right. (In 1993 I was part of a studio build for which I spent 2 solid years on just in the construction) I am also aware that a slab is best, so maybe I will still do that. The area underneath can support a slab with the extra joists put in but probably right now only up to 3". I guess a 3" slab would be better than nothing no? Thanks guys for your patience, -Christian Stonehouse (Saltspring Island, BC Canada) http://www.myspace.com/barnrecording

thebarn wrote:

Thanks guys for your patience, -Christian Stonehouse (Saltspring Island, BC Canada) http://www.myspace.com/barnrecording

make sure that you put all of that into your profile here when posting. the guys here are ridiculously helpful and insanely knowledgeable but they are very specific about making sure that all of the forum posting guidelines are followed. (: greetings from very close to your province! -= george =-