a studio in a STILT house on a hill??

so i am building a room within a room in my 2 car garage in los angeles. the garage is on a concrete slab BUT the whole entire house is one of those LA hillside houses on stilts. so, under the garage is just open space at the moment (although a wall is being built around the stilts but i am not certain how serious it is besides cosmetics). if i want isolation i have no choice but to float the floors then, do i? anyone have experience building a studio in a stilt house??? thank you!

pictures...we need pictures...your building on a concrete slab that is elevated...because that is how it reads...pictures :)

xSpace wrote:

pictures...we need pictures...your building on a concrete slab that is elevated...because that is how it reads...pictures :)

that IS what i am trying to say. i don't have a photo of this house yet but in the meantime it's basically just like the houses on the left of this photo (but with more supports and a HUGE "X" of two steel beams across the front). thoughts?

My thoughts are that you have to determine your weight /load limits on this structure, you don't need a floating floor, how big is the area to build in, how much is your budget...are there going to be any structural items in the way, etc., etc.

xSpace wrote:

My thoughts are that you have to determine your weight /load limits on this structure, you don't need a floating floor, how big is the area to build in, how much is your budget...are there going to be any structural items in the way, etc., etc.

+1 and how much isolation does the OP need? Is this a "I heard a floating floor is needed for studio" sort of question? Andre

Andre, it's not exactly a "i heard i needed a floating floor" type of question. i know that if the concrete slab was on the ground i'd be good as far as the floors are concerned, but since it is just a concrete slab almost floating in mid air wouldn't that just make it more of a gigantic drumhead per se? i spoke with an audio specialist / studio consultant who told me to do the hammer test and hit the floor lightly with a hammer and go outside of the garage with it closed to see if the hammer sounds like i am in the room with it. surely it sounded like i was right there even 7 feet away from the front of the garage door which leads me to believe that sound is transferring through the entire structure of the house via the floor hence why i am thinking i might be forced to float the floor. ultimately my goal is to be able to monitor loudly, sing at all hours of the night, and track guitars without ever bothering my neighbors who are around 20 feet away to the side and 20 feet away from the front of the garage. ultimately, if i could get it good enough where i could track drums that'd be incredible but i don't know if that is realistic. of course i am building room within a room but i was HOPING originally not to have to float the floor. the raw space is 16x22x7 foot 9 inside so i am going to build a room within a room with 2 feet of air space on all sides except for the ceiling because i need the height too much. but considering how fast sound travels through concrete i know that the floor would certainly be my weakest link. the garage is rated for parking 2 cars so weight shouldn't be a problem. the only really heavy thing i have going in the room is a yamaha upright piano and a couch. i have no huge console and i don't have a ton of big racks of gear just a desk with modest outboard. the main weight will be in the actual construction. i considered using the super expensive quietrock because i am thinking one sheet of it would be lighter than 3 sheets of 5/8" drywall.

"the garage is rated for parking 2 cars so weight shouldn't be a problem. the only really heavy thing i have going in the room is a yamaha upright piano and a couch." It won't be without it's challenges...but you really have to get a better number on the load limit than a couple of cars...what is that weight about 4-5 tons? Is that including the piano? For me, what you are wanting to do is add to an already existing dead load. Things like vehicles and such are not specifically intended to be parked...forever..so that could/can influence what your limits may or may not be...follow me? Even still, the weight you will impose on this structure can modify how it was intended to resist the environmental conditions that exist in your area. Things like erosion, flooding..these have to be given their due respect in order to be able to re-hab a structure and have it remain safe for you and those that might be around/under it. I'll say this before I say the next thing...kinda should have gone without saying right :)? You gave measurements of 16X22X7'9" right? As a rule, your isolation will be reduced to the smallest distance from one hard boundary to the nearest boundary. What that means is that your over head area will dictate what your isolation will be since it will be the smallest component in your mass/air/,mass assembly (remember, we still have no visual on this so speculation is the word of the day/week). Just using some hack numbers I have check this out: I already mentioned 4-5 tons for vehicles. The framing for your walls and ceiling, plus quietrock @ one layer is roughly 5100 pounds. That is approaching half and better than your actual supposed limit of this as yet to be determined load limit. That doesn't take any additional weight into consideration...that piano, insulation, bodies, the couch...doors, HVAC, electrical...equipment, etc...cheeseburgers...what have you. There are ways to do this, but you have to be realistic in what this structure can do for you....the last thing anyone wants is to get involved in a great project that collapses because someone forgot to take gravity into the equation.

thanks Brien. i'll be talking to the inspector who last assessed this house in the next couple of days to find out the weight load limit. thanks for the clarification on the roof thing. i knew that but i am stuck with that space since the ceiling is low. sucks. i still don't know if i should float the floor though. i've successfully built a studio before that ended up with great isolation but it had less oddities to it than this garage. i have Rod's book coming in the mail saturday morning btw.

There is a method, possibly pioneered by Philip Newell, that installs rigid insulation on the floor and then you add additional hard surfaces...plywood, flooring to make a decoupled assembly that reduces the in/out connection of vibration. I think Rod has been working on a more defined usage of this, and it is (I think) included in his second edition of his well received book.

xSpace wrote:

There is a method, possibly pioneered by Philip Newell, that installs rigid insulation on the floor and then you add additional hard surfaces...plywood, flooring to make a decoupled assembly that reduces the in/out connection of vibration.

I believe i have read Ethan Winer talking about using this method. i figured i'd float the walls if i did it with the other method but this seems like it would only work if i floated the floor. the thing i don't get then is that the walls would still be sitting on the concrete floor so wouldn't that just form a channel for sound to head right out the concrete floor?

Trying to break a hard connection between a wall and where it is attached is, well, hard. I have seen people do all kinds of things that I can't say if the methods do or do not have any effect. A dense caulk like butyl, underneath the floor plates is going to work better than say a latex caulk, but neither of the two will make the walls float. But with any floating of a floor, the new framed walls still want to sit directly on the "floated floor" to create that "room in a room" fully decoupled effect.