building studio (slab on grade), request info on floor.

hi there, I'm new to the forum - so first off, hello everybody (; I've tried to follow the guidelines, but please bear with me, as it's my first time....posting. heh. (; I've recently undertaken a dream of mine to own a recording facility, and the construction IS currently underway, the footings have been poured, the walls should be poured within the next week, then backfill, infill, for a slab on grade finish - most likely with pex piping for radiant floor heating. (done in area's so i don't have to heat the whole facility at once!) the facility is 1920 square feet, with a trussed roof. and will not have any interior load support walls or columns. I live in an area on vancouver island where there is NO applicable building code (you can build what you want how you want), altho i'm trying to build as close to traditional/normal standards as possible. (ie: 2x6 framing for exterior walls etc). my original plan was to completely slab on grade the the entire 1920 square feet, then with decouplers or a neoprene matting build a wood floor on top for each of the individual studio room for acoustic isolation - this would also allow excellent routing of wiring etc. However it was suggested to me (by a non-audio person mind you) to perhaps just pour individual slabs for each studio room, that way none of the slabs for each room would be touching one another for acoustical transference (seperated by a styrofoam? or similar material) the benefits would be not building a wood floor that might have the tendency to creak, leak sound, and better transference of the radiant floor heat. on the downside, routing of the wiring would have to be "over the top", studio resdesign/reconstruction would be difficult, because of slab set up particular to the rooms etc., and of course the acoustical properties? (which i don't really know about in regards to sealing the room acoustically right to the slab?) I've never heard of this method being done, and perhaps it's just someones fantasy? but i'm closing on the time where this decision has to be made. I'm leaning more to building a wood floor on a "normal" slab that spans right to my footings. but I want to know if the "other" method is ever done, and the benefits or downfalls, or impossibility of it. thanks in advance.

oakdown wrote:

hi there, I'm new to the forum - so first off, hello everybody (; I've tried to follow the guidelines, but please bear with me, as it's my first time....posting. heh. (; I've recently undertaken a dream of mine to own a recording facility, and the construction IS currently underway, the footings have been poured, the walls should be poured within the next week, then backfill, infill, for a slab on grade finish - most likely with pex piping for radiant floor heating. (done in area's so i don't have to heat the whole facility at once!) the facility is 1920 square feet, with a trussed roof. and will not have any interior load support walls or columns. I live in an area on vancouver island where there is NO applicable building code (you can build what you want how you want), altho i'm trying to build as close to traditional/normal standards as possible. (ie: 2x6 framing for exterior walls etc). my original plan was to completely slab on grade the the entire 1920 square feet, then with decouplers or a neoprene matting build a wood floor on top for each of the individual studio room for acoustic isolation - this would also allow excellent routing of wiring etc. However it was suggested to me (by a non-audio person mind you) to perhaps just pour individual slabs for each studio room, that way none of the slabs for each room would be touching one another for acoustical transference (seperated by a styrofoam? or similar material) the benefits would be not building a wood floor that might have the tendency to creak, leak sound, and better transference of the radiant floor heat. on the downside, routing of the wiring would have to be "over the top", studio resdesign/reconstruction would be difficult, because of slab set up particular to the rooms etc., and of course the acoustical properties? (which i don't really know about in regards to sealing the room acoustically right to the slab?) I've never heard of this method being done, and perhaps it's just someones fantasy? but i'm closing on the time where this decision has to be made. I'm leaning more to building a wood floor on a "normal" slab that spans right to my footings. but I want to know if the "other" method is ever done, and the benefits or downfalls, or impossibility of it. thanks in advance.

Oak, yes the other method is done. That's the nammer in which I constructed Tony Bongiovi's "Power Station" New England. BTW - I don't know why you say that "routing of the wiring would have to be "over the top" - we insstalled all of the low voltage wiring beneath the slab using conduits which then swept up into the walls. Only our line voltage wiring ran above slab. One other thing - Just for the record - this studio I refer to is a world class recording studio - not just your average joe - the building housing the studio and the studio "room within a room" was about one million dollars (US) and that did not include gear or the low voltage wiring. Take a look at the main room: Rod

interesting and thanks for the reply rod. just curious what you seperated the individual slabs with then? was it styrofoam? how thick? also what are then the principles for sealing (acoustically) the wall studs to the slab? any input, or suggested reading appreciated (; thanks again.

oakdown wrote:

interesting and thanks for the reply rod. just curious what you seperated the individual slabs with then? was it styrofoam? how thick? also what are then the principles for sealing (acoustically) the wall studs to the slab? any input, or suggested reading appreciated (; thanks again.

Oak, I don't want to sound like I'm prostituting myself - but if you want clear answers - pick up my recent book on the subject - or do a search here on sealing wall assemblies: Sincerely, Rod

rod gervais wrote:

oakdown wrote:

interesting and thanks for the reply rod. just curious what you seperated the individual slabs with then? was it styrofoam? how thick? also what are then the principles for sealing (acoustically) the wall studs to the slab? any input, or suggested reading appreciated (; thanks again.

Oak, I don't want to sound like I'm prostituting myself - but if you want clear answers - pick up my recent book on the subject - or do a search here on sealing wall assemblies: Sincerely, Rod

no i don't mind the prostituting at all! in fact i did end up picking up your book... however i still have a few unanswered questions... in reference to your dual frame assemblies on page 59 - you never really specify a good/recommended value for the A in the M-A-M, the floor construction WILL be independent slabs, and i understand the spacing of the slabs apart from one another will determine what value A should be - so i'm wondering - Is 2inch better than 1 inch? is even more space better? (altho obviously less space efficent for the studio) In another post I saw someone saying 2inch...also is their ANY benefit to doing say 2x6 construction over 2x4 - if the only difference is a couple of inches of insulation? i would think not, but if there is - perhaps i would consider that for my drum room and control room. as for the material that you use for seperating the slab - on page 41 you call it "expansion joint material" with a caulk seal at the top. - what is this expansion joint material? is it the same 2x8 foam insulation for seperating slab from foundation wall? could i essentially run pads of that 2x8 foam around each slab? or is there something better. in reference to the question above, it's the width of this expansion joint material that i'm wondering about to set up the proper MAM distance. other questions... in canada, on constuction sites (for general purposes), i often see them using OSB (or plywood) on the walls, and seperating the say the top row of boards from the bottom row with a 1 inch gap... I believe for ventilation purposes? obviously this same technique would seem ridiculous in studio construction where you want everything sealed...any input on that would be great. the studio is being built on 5 acres, which is fairly quiet area - i'm hoping to get away with only 1 run of 5/8 plywood on the outside (plus cedar/undecided siding) altho i could run 2 layers if needs be, in such a case, I imagine i STILL wouldn't want that 1 inch gap even on the first run of plywood correct?. just build it as tight as possible? finally (and i'm sure it's been asked so i'll do a search too) much benefit to roxul safe n' sound, over regular insulation? i'm thinking of going with the roxul just because of the ease of handling (no itchiness). thanks again.

[quote='oakdown']finally (and i'm sure it's been asked so i'll do a search too) much benefit to roxul safe n' sound, over regular insulation? i'm thinking of going with the roxul just because of the ease of handling (no itchiness). [/quote] Two points here: 1) There IS itchiness with Roxul!!! I know, I put up two pallet loads of it. I'd use the same precautions with Roxul (or any mineral wool product) as I would for regular FG insulation (long sleeve shirts, dust mask, goggles. At a minimum, put on a lot of baby powder before starting. It fills your pores and prevents the little "hairs" from getting in. 2) As I understand it, if your insulation's purpose is for heat/cold insulation or for damping, standard "pink fluffy" insulation is fine (preferred?). When you are making acoustic treatments (wall absorbers, ceiling clouds, etc) mineral wool or RIGID fiberglass is what to use. len

cool thanks for the headsup.. i'll be careful! i'm still looking for more info in regards to this "air gap" i've searched for "air gap" "air space" "wall space" and not really found too much info! reading some of the essential posts that did turn up, I learned that more air gap - provides more "spring" which is obviously better.... however what i need to know, is whether 2 inch gap is enough! that is 2 gypsum 2x4 - with insulation 2 inch gap (between 2x4's in double wall construction) 2x4 - with insulation 2gypsum or is that too little "spring" ? in some other posts i've read of 5 inch gap etc. In one post i read that the spring is actually the sum of the distances from one gypsum board to another (so technically i would have 10 inch air gap - if you consider a 2x4 being a true 4inch) ? too much too little? any help appreciated as indy slabs will be poured in a week and a half, so i'd have to adjust accordingly by then

Oakdown, You have to learn the proper calculation. :-) The insulation counts as "air" too so what you have is: 3 1/2 " (2x4 w/ insulation) 2 " gap between studs 3 1/2" (2x4 w/insulation) For a grand total of 9" between the backs of the gypsum panels so IMHO, you've got plenty of air in your mass-air-mass sandwich. len

For improved low end transmission loss performance, there is a benefit to further separating the frames. Having them separated by 5" gets you 12" of an air gap, and that's even better. 8) --Keith :mrgreen:

To amplify what Keith said, the "bigger is better" idea is true up to a point. which (if IIRC) is about 12" (total gap, not the distance between the studs). After that, I don't think you get much of a gain for increasing distance. len

Yeah, I think 12" is kind of a "sweet spot" in terms of having an appreciable difference with minimal space invstment. At least that's what I recall reading once or twice. --Keith :mrgreen:

Using 3 layers of 5/8 wallboard each side on double frames as an example, air gap of 8" (1" between frames) STC 73, 34 dB TL @ 50 hz, mam 34 hZ air gap of 10", STC74, 35 dB@ 50 hZ, mam 31 hZ Air gap of 12", STC 74, 37 dB@ 50 hZ, mam 28 hZ Air gap of 16", STC 74, 39 dB @ 50 hZ, mam 24 hZ Air gap of 24", STC 73, 42 dB @ 50 hZ, mam 20 hZ Air gap of 36", STC 73, 46 dB @ 50 hZ, mam 16 hZ. All from Insul's old demo, no longer available. AS you can see, LF TL continues to improve mainly due to lower mam frequency; so if you're wanting better drum iso, wider air gaps can be useful if you have the space to give up. According to the same calculator (typically somewhat optimistic) replacing the outer 3 layers of drywall with 8" sand-filled concrete block raises these numbers to STC 94, 59 dB @ 50 hZ, mam of 12 hZ. THis is with 36" air gap. Drums would have to be louder than about 115-120 dB in order to be audible outside such a wall, assuming all other paths as well built... Steve

STC 94? Holy Hanna! 8) Steve, if you don't break ground on your own project with those 36" walkable gaps before I finish mine, I'll... I'll... Well, I don't know what I'll do! :lol: --Keith :mrgreen:

Down to only 112 projects in line ahead of that one... :?

You need an intern! :lol: :twisted:

i wanted to thank you all for your quick and prompt responses!, so i've decided to keep things somewhat simple.. which lands me between the two suggested amounts.. (more than 9, but less than 12!) since the outer wall will be framed 2x6, with all inner walls 2x4, and a 2inch foam pad gap between footing wall and interior slab, that should yield a 5 1/2 + 2 + 3 1/2 = 11 inch gap. for the interior wall to interior wall, i'll run two 2" foam pads seperation between the slabs, giving 4 inches there which should yield 3 1/2 + 4 + 3 1/2 = 11 inch gap! keeping all my gaps somewhat equal! hopefully this will yield results that i'm happy with - while maximizing space (it's amazing how fast 1920 square feet can start to seem small when building everything double!) in a worse case scenario, i could always build each room even smaller (even after the fact, as the slabs would be seperated i could start the framing further inside rather than at the edges (altho that's where I've trenched for wall strength - to support the ceilings etc) so you guys know i'm not just flappin, I'm gonna upload some pics soon of what i got going on so far, as well as my suggested floor plan layout (open still for last minute suggestions!) thanks knightfly for your intuitive post as well. cheers

Wow, what a beautiful setting! I can't wait to see this come to life! 8)

Yeah, you oughta consider at least one picture window if you can - done right, it won't impact isolation much at all for "normal" studio construction... Steve

wow! tell me it gets easier, once you are out of the dirt and sand, and onto framing! and dodging glue boogers. i'm buggered after just a few days of crawling around working on my isolated slab footings, cutting foam, and dealing with mesh, pex piping and sandy balls - yea i said it. i'm doing my isolated slab in a few pours (is their any other way really?) - the first two rooms are the control room, and the drum room. i'll then make a small foam divider between the two the small chunk being a vocal booth, the larger area the main tracking room, then to the other side of the control room will be a machine room, and another smallish vocal/cabinet room. i'm trying to do it all correctly (see trenches with rebar) but with scheduling the contractors i've ended up a wee rushed (planning is hard here) already i'm going to have to route the drum room audio wires over the top or elsewhere, i simply don't have time to put it in the ground, and lead it back to the machine room. ): it was last minute that i threw some pipes into the control room! but i'm glad i did...believe it or not, it gets poured tomorrow, i gotta tear down the existing footings the next day, and prep the whole other area! in a day (pex piping and all) haha wish me luck. thanks for the kind comments on the location, yea it's pretty nice here on vancouver island ((; their will be a picturesque window (had to be done right?) off the Main large tracking room, on that stepped corner (see pics below) i'm planning on building 14 foot exterior walls, so i should have plenty of space to build inside (12 foot or 10 foot heights) and have nice long windows in that stepped radius corner. hopefully it all works out, and atleast the exterior before i run out of moneys ): moooo anyways enuf babbling onto the pics

Cooler than cool! 8) 8) 8) I don't see a floorplan in your thread anywhere. I'm wondering if you might have some other non-adjacent rooms that you could also pour at the same time as the one you've already formed. :roll: I think your project thread is the first on this forum to do isolated slabs for multiple rooms, so it's fascinating to see it taking shape. Thanks for posting the photos and details. Keep 'em coming! 8) For what it's worth -- if there's anything I learned about my concrete prep, it's akin to painting -- prep work is the lion's share of the work, that's for sure! :roll: --Keith :mrgreen:

Hi, I was just curious about why you decided using a slab on grade, what sort of frost line you have in Vancouver, and if your footings are below that frost line? I understand around here in N.E. that footings are usually required to be below the frost line, which usually means that most all houses here have full basements below ground (I guess it's easier to ensure that all parts of the footings are below the frost line)... I think there is an exception if somehow the footings are 'protected' from frost heaves... Anyone know more details about this stuff?? K

Great question. I wondered the same thing subconsciously!

hey thanks for the interest guys! I don't want to feed you a bullkucka answer on the permafrost - in all honesty - I don't really know HOW deep (or if there is any at all) it goes here on vancouver island (i'm not in vancouver itself, despite how my profile named me). Vancouver island bordered by oceans - really doesn't get that "cold" over the winters, it's rarely below 0 degrees (centigrade i'm talking about for you americans) however it can get down to about -5 or -10, but those instances are really quite rare, and would never extend for a period longer than a week. It does rain a lot tho (; Unlike alberta or other regions of canada, I can't really see the permafrost (if there is one) going much below a couple inches. i've attached some pictures of HOW deep my footings actually go (3 or 4 feet in places), (before the infill, and backfill) so you'll see i'm pretty well entrenched.. it took a LOT of dirt/rock and sand to get back to slab level heh. i've also attached some pics after the first pour! the concrete finishers seem to pay a lot of attention to detail, and these pics are even BEFORE the final sciff! i shoved some anchor bolts in for the interior walls... and you'll see where i had to make a tench for the pex pipe (so it could make it to the other studio rooms, during the pour). they also poured the loading bay area (a small car/truck/van pad basically) that loads into the main room. sorry about the lack of plan, i'll have to screen cap an autocad detail sometime. as far as the question - why did i choose slab on grade? i didn't want to have to deal with the acoustics of "crawl space" - the studio is not part of a house (technically.. their will be a living space attached... but the studio area has no plumbing (meh, if you don't count the radiant floor heating), and is specifically designed for studio space only).. initially i was gonna pour one big slab, and build seperate floors, (that's what this post was initially about until rod set me straight) - i do a lot of the work myself, so altho it was more work/time/money, i thought i'd do it right with isolated slabs - trenched to support wall and ceiling weight. i guess another way to go about it - would be to still trench for your interior walls, but pour one BIG slab all at once, then cut it down the middle of your trenchs (hopefully you have good dimensions) and slip some sorta foam/rubber/caulk in their.. i'm using r10, 2 inch thick - i use 2 between interior walls for 4" and just one by the exterior walls - keeping all air gaps the same. second pour is on friday... so i'll have more pics then.. (is there a limit on pics?) it should be nice when the foam is sandwiched between the opposing slabs. cheers. p.s. should i be posting this non-question stuff in a build diary or somewhere other than here?

Looking fabulous, Oakdown!!! 8) I'm by no means an expert on concrete foundations... But here's what I do know.

• "Frost line" is defined as the level down to which the soil will normally freeze each winter in a given area.
• "Permafrost" is defined as a thermal condition where ground material stays at or below 0°C for two or more years. (You definitely do not have permafrost.)
• Failure to dig foundations down below the frost line can cause frost heaving, dislodging the building at least slightly and causing damage which may become a serious threat to the building's structural integrity.
• From what I can gather in my Google searches, Vancouver Island, Canada, has a high frost line, so I'm guessing that a foundation depth of one foot (30.5 cm) below grade would suffice.

oakdown wrote:

. . . it can get down to about -5 or -10 . . .

...That's 14-23°F folks... ;-) (I love Google's built-in calculator!! 8))

oakdown wrote:

. . . i guess another way to go about it - would be to still trench for your interior walls, but pour one BIG slab all at once, then cut it down the middle of your trenchs . . .

It sure would take one heck of a big concrete saw blade to cut down 12-14 inches. :roll: It would have to have a diameter of about 30 inches! :shock: I really think separate pours are the way to go.

oakdown wrote:

second pour is on friday... so i'll have more pics then.. (is there a limit on pics?)

We love pictures!!! 8) 8) 8) 8) The only limits on pictures that I have seen on this forum have been file size on a file-by-file basis (governed by the software) and a maximum width of 700-800* pxiels wide (governed by the moderators). (*I've seen three different numbers -- I suggest staying under 700, which you're already doing.)

oakdown wrote:

it should be nice when the foam is sandwiched between the opposing slabs.

I've often wondered if EPS foam, like the kind I think you are using, is an effective isolated slab perimeter board in terms of maintaining the isolation you're working so hard to achieve. Would the EPS foam, undoubtedly under lateral pressure from the concrete pour, and thus "pinched" between the slabs, act to short-circuit the slabs together? :roll: I don't have Rod's book in front of me, but perhaps you could look that up and/or he could comment on this. In my case, my isolated slab has a 2 to 4 inch air cavity around the entire perimeter. In retrospect I might have done that somewhat differently... :roll: In the event that it is determined by consensus that having the EPS foam permanently fused between the slabs is a bad idea (and I'm not saying it is a bad idea -- I'm just posting the question and a possible solution for it), then perhaps you can use a blowtorch to burn all of the foam before framing begins, leaving behind a gap between slabs and some soot. Obviously you'd want to take precaution so as to not breathe in any fumes, burn yourself, or set fire to anything else! :shock: If you do end up with just a gap, you can do something like what I did to seal the gaps around your slabs, preventing moisture vapor from migrating into the area between your walls. Regardless, you're quite possibly at more risk for termite infestation. I don't suppose you had your soil treated with termiticide before you started pouring your slabs...? :roll: Sorry I didn't think of this earlier. :oops: You might be able to get the rest of your site treated before the rest of the slabs are poured. But be aware that the treatment doesn't last forever (about 5 years for Termidor). Here's the point in my marathon thread where I got my soil treated with termiticide. After my concrete work was finished, I installed a home-made termiticide delivery system so that the perimeter of my slab can be retreated every five years. Some might think what I did was overkill and silly, but once I learned how destructive subterranean termites can be, I decided I didn't care how silly it seemed. :P

oakdown wrote:

should i be posting this non-question stuff in a build diary or somewhere other than here?

Your questions are most welcome within your thread because it is easier to see the context of the question. Often the answer for one case is different in another due to the availability and/or relative pricing of building products, among other things, including anything special about your project. That being said, sometimes a question does suit itself to be in a thread of its own. I guess it depends on whether or not the question pertains to your specific scenario, or if it is more general in nature. That's my take on it. --Keith :mrgreen:

thanks for the kind comments sharward, and the feedback on my questions to boot! as far as that insulation stuff goes, i can't really see it transferring to much acoustical energy from slab to slab- it is a firmer foam and i wouldn't mind hearing feedback on it. Rod's book was used as a reference, and i actually asked (in this very post somewhere back on page 1) WHAT expansion joint material should be used between indy slabs... but i got no answer.. as that is all rod's book describes "expansion joint material with caulking" (at the top). I've been very careful to NOT even run rebar from slab to slab, each little pad has a couple of it's own isolated little loops of rebar in the trench - same with the wire mesh... today was sheer buggery... i had to remove all the footings from the poured slabs, and build up the entire remaining portions of the studio, pink foam, wire mesh, and cable run tubings. not to mention hanging the rebar in all the trenches with ties (you can count on concrete guys to hook it and pull it up, but i just feel better tieing it all together in a nice cavity so you know it's gonna sit proper when the concrete gets poured) i had to have everything prepped and done for 2:00pm so the pex piping could go down for the remaining areas... yah physically i'm pretty much kaput haha. anyways some more pics - and the remaining slabs get poured tomorrow (pending weather i imagine). exterior framing by the weekend.