Has anyone had great isolation on a floating concrete slab??

[Govinda]

First of all I'd like to say hi to everyone! Thanks for this awesome site john, and of course everyone who contributes!
My names govinda and i'm a musician and studio owner ..I have been lurking around these forums for quite some time, I have built 2 recording studios, i'm 28 years old on the gold coast Australia ...john lives not far away! hehe..

I am building a house and studio from scratch with around a 60m2 (roughly 180 sq foot) studio space, john has designed a great studio!
Due to the steep nature of the land I have already gone over my house budget by 30k...before even starting
Originally I was going to cut out of the hill and fill to make a flat pad for the concrete slab to be poured on and retain...but I have since found that I can save up to 20k if I construct my slab sitting on footings in the ground (south side) and floating in the air supported on iron beams and steel posts on the north side.

The question is Regarding the concrete slab the studio sits on...

The outside shell of the studio structure will be concrete floor, core filled 8 inch besa block walls (load bearing walls), and concrete ceiling, all concrete slabs will be a bondek style of construction (for those of you unfinaliar with bondek, its like roofing iron layed down and we pour cement on it to save costs on concrete formwork). Depending on which way I go ceiling height will be 3.6 m to 4m, slabs are 4 inch thick

It can be expensive and hard to float the studio floors when you can have a concrete floor resting on the dirt and achieve a simalar result when floating the studio frames on neoprene etc, I have heard "if the floor was concrete and resting on dirt, alot of the sound would travel into the dirt "...seeing as I have close neighbours 4 meters (12 feet) to be exact and I record alot of drums.. well it seemed like a cheaper option

Will I get the same result if my floors 4 inch slab is floating on thick iron beams and steel supports going into the ground, and the studio is of a floating floor type?? My logic says no, my wallet says yes way...
I thought an inbetween option could be to have the area under the floating slab sealed and covered by besa blocks (to stop the floor vibrations getting outside??) .... but its also bad for mold fungus etc..
There is also a spray to stop conrete vibrations as well as fiberglass absorber pads to put under the slab there it comes into contact with the iron beams..

So has anyone had great results with isolating drums from neighbours when there studio shells slab has not come into contact with the ground?

What would you guys do if you were me?? (dont say buy a gun hehe) I am willing to float the studio floors to save house construction costs, I can take as long as I like to build the floating floor and studio and I have building experience.
so I guess there are a few options but I dont know how sound-proof theslab in the air will be?? If you guys think its worth the 20k I am willing to go with the 1st option (cut and fill and retain)....but he cost has thrown a spanner in the works!!!
Many Thanks!
Govinda


btw...I can send pics diagrams etc?? if it makes it clearer.

[Govinda]

Maybe im not being clear?
too much info?
lame title hehe
anyways here are some pics to clarify the dilema!

What i'm really trying to find out is if the floating concrete slab method in my pic, and a floating separate room within is gonna isolate drums from neighbours good enough to not tack them off!
Is it possible??
has anyone done what im trying to do with a floating concrete subfloor and had great results??
I am really woried about the floor floating in air and the loss of isolation!

Govinda

ps. the internal ceiling is 4 inch concrete and the walls are core filled besa blocks 8 inch.

[Kaj]

Hi Govinda! How is tomorrow, It is still Saturday here in Sweden. I like the subject you bringing up. I am not even close to your stage yet. I want to know more about the best compromise Cost/Accoustic for design and build a home studio. My intention are to get the studio to be the first to design and later draw the rest of the house around, over under or what ever would be the best. Do you have any good links to share about the step one to build a studio from greenland project start?
Thanks, Kaj.

[knightfly]

Sorry for the delay, my work schedule doesn't allow much time for posting on some days (12-hour days followed by 12-hour nights) -

Basically a floor is just a horizontal wall, acoustically speaking - if you're using a 4" slab that's in free air, that's one of two leaves of mass required for optimum isolation. The second one would be a floated floor - in both leaves, as in walls, more mass/more space between leaves/more decoupling, all of these can add to performance. I did calculations based on EPDM pucks resting on your 4" slab, then 4x2's on edge resting on the pucks, then 3/4" exterior grade plywood, a layer of poly sheeting (to keep the plywood from contact with the top layer) then pouring another 2.5" slab on top - this gives a mass-air-mass resonance of around 21 hZ, (the lower the better) and has a Transmission Loss of 45 dB from 50 to 160 hZ, increasing evenly upward from there - since human hearing requires about 54 dB at 50 hZ just to be audible, this means you would have to generate around 99 dB SPL at 50 hZ just to hear it outside the studio - at 115 dB spl inside the studio, and assuming the other walls/ceiling are built as well, you would generate a sound level that's roughly equivalent to NC 40 right outside the studio - NC40 is the center of acceptable range of noise for living quarters, and we've not gotten to the INSIDE of the neighbors' house yet - so the suggested construction should work for you.

For walls that can keep up with this, you'll need about 12" air gap between double framed, minimum double 5/8" gypsum cladding on the outside of each frame - as with the floor, filling with insulation is necessary and NOT optional.

There's more, but I'm on night shifts and need to sleep - I'll get back to this about the same time tomorrow... Steve

[Govinda]

Woo Hoo!
Thanks so much Steve! This is looking ALOT better than 1st thought!
I look forward to hearing more about this!
Sorry to hear that your working so damn hard...
Maybe post some more stuff when your not so overloaded...I'll tell the engineer and building designer that we will be going with the studio slab being supported with iron beams and steel posts!..that will get my house plans finished! and allow me to spend some money where it should spent, the STUDIO!
The floating floor that you propose sounds great! btw there no way im putting all this work into it and not gonna insulate, but thanks for being super clear! The 12 inch air gap between walls is quite large..but i'd rather lose some space in the studio than have the neighbours or my wife complain!! Fantastic Steve!!
As for the double studs for walls do you mean instead of 4x2's use 8x2s?
As I understand it, the walls would compromise of this...starting from the outside: Besa block wall, redered and painted on both sides, 12 inch air gap 4x2 stud with 2 layers of 16mil gyprock and insulation...is this correct according to you plan steve??
Thanks a million!
Govinda


Message for Kaj:
Seeing as you just signed up...Welcome to "The BEST place" to find and share infomation about building studios! (well in my opinion anyways and many others ) Not to mention designing studios, acoustics, speaker design and placement among others!
If you take the time to read through this site you will find it's full of amazing information and tips to build studios...studios cost money ...but depending on what your needs and budget are ...there are many possibilities...plenty of cost saving tips are here all through out this site!
Building a house around a studio design can be great, but it is amazing what you can do with a little space in an existing area etc...my studio design was made to suit the space I had allowed for due to space and budget!..it was really secondary to the house.
Hope this helps!
btw..hows the weather in beautiful sweden?
hello from tomorrow!
Govinda

[Kaj]

G´day Govinda and others out there. Yes you´re right I´ve just signed up, but have used this web site for some time. There is a lot of good stuff here, thanks John and the rest of you guys/Sheilas.
I must say that the main reason why I jumping in here and now are that you starting a project from scratch and therefore of my interest to follow your project in the comming future. I´m sure that I will learn a lot.
My plans to build my own home studio are one of thoose 5 years plans, but I will get my ass into it.
My thoughts and needs today is to get a CR that should be suitable for listen to others recordings, and also do mixing whenever my band has recorded some new stuff.
I have heaps of old 4 track recordings since early eighties that I want to remix but, my current home studio are more fit as a storage than a music room. Living in a appartment that have no options of do any treatment.

Yes you are right about that it is possible to get a good home studio in an existing room (seen a lot of postings here). But I just thought that I could create a more perfect starting point (cutting a corner ) by the design of the outer room (angles, room mode building material) before building the inner one. That would maybe save me headache caused by not doing my homework now.

BTW it is bicycle weather in Sweden, i.eg not snow yet! And we have catched up in time it is Sunday here.

[Govinda]

Hey Kaj,
Your welcome for jumpin in!
I agree if you can plan a studio in your building why not!
Thats what i'm doing!
And I believe that I will get a fantastic result in the end!
When I start building I will be posting all the pics on johns studio building site!
I know how you feel about a compromising space for mixing...my current mixing room is no more than 3.4m x 3.6 m and its a pain in the ass to mix in I have some absorbtion but thats it...I am currently working on 2 albums and a film score and its hard to tell how good/bad it is sounding!
hehe...i'm just very cautious when I mix here!

I cant wait for my new control room!! Its going to be a dream to work in!
Glad its not snowing!!
and its monday here now by a few minutes!
If there any help you need i'll be glad to try and help you with studio/house design etc..
Here are my studio plans that (mostly) john and I came up with!
Cheers,
Govinda

[knightfly]

Is this the besa block you're referring to? Doesn't sound too super strong to me -

http://www.cidb.org.za/initiatives/Part ... 20Besa.pdf

Also, no mention of STC rating on its own - for a solid wall that would depend almost totally on mass. If you have any figures on the mass of your blocks, I can get a pretty close idea of whether you'll need to give up that much space between walls or not.

As to elevated or cut in floor, if you can swing it the cut in should be quieter with the same amount of construction, but probably not by much - if elevating a slab on steel, keep in mind that you'll be floating another concrete floor over that one, and you need to keep the support beams sturdy enough and closely spaced enough to be able to take the point source loads induced by the resilient pucks which will be holding up the weight of the upper floor - basically, the pucks need to line up with support beams. Heavy sound-deadening paint for beams wouldn't hurt anything either -

Since you're already working with an engineer, they should know more than I what will be necessary to support things - if they're not versed in sound control, however, it's really easy to get everything ringing and flanking sound into everything else - too much spring material can be worse than not enough for example. Ideally, you want around 20% compression of the floating material; needless to say, there are a few calculations involved here too -

I've still not found anything good on besa blocks - I'm assuming they're similar in mass to adobe, I'll see if I can find more on that later. Right now, I'm off to bed... Steve

[Govinda]

Hi steve thanks again for the info!!!
I think besa block is just an australian name for a hollow concrete block.
The stc is 45 when not core filled...my engineer will be the one deciding whether the blocks will be core filled...they are 8 inches wide.
They are very strong and are a large block, the application is usually in retaining and supporting buildings....in fact alot of multi story unit blocks will use besa block for the walls and besa block colums for weight supports...its very solid!
The link you sent was a different block.
Sorry steve..I found out its actually spelt besser..

http://hansonbp.biz/freedom.aspx?sdaID=42&pid=215

I have sent an email for more info and will give you that asap!
Many thanks again steve,
Govinda

[knightfly]

No prob - BTW, if your engineer isn't acoustic trained he should know that if you do NOT fill the blocks, you should NOT put a second center of mass inside separated by an air/insulation space, or you will WORSEN the isolation at lower frequencies by several dB - so if you want good isolation, this means ALL of the construction has to be designed that way and that the "weakest link" theory applies here - if this means you need to beef up the support to take the weight of filled blocks, then that's what needs to be done.

Waiting for your info on the blocks... Steve

[Govinda]

Hey steve!
Sorry it took so long to get back to you...Its been hard to find the info! I made a few calls and could only really find out this on the besser blocks: The stc rating is 50+ and the weight of a standard 190mm x 190mm x 390 block is 14 kg...Is this any help steve?
Thanks again,
Govinda

[knightfly]

Yeah, that particular block is pretty standard around here, it's just referred to as 8x8x16 concrete block. If you leave those webs hollow, as I mentioned you shouldn't put any other mass except directly against the blocks - otherwise, you'll get a triple leaf situation which will worsen low frequency TL quite a bit.

If possible, you need to allow for enough support to be able to FILL those blocks with either grout or sand, so that they act as a single mass wall - then, you can move in at least 8" (12 is better) for your inner, double gypsum second mass area, insulate fully between, and you're set... Steve

[Govinda]

Thanks so much steve!
I think im pretty clear on what the deal is!
I'll make sure the block walls are filled with concrete or sand and I will go with that 12 inch air gap in the drum room as you mentioned!
I want the best soundproofing possible! And my neighbour is really close!
By the way if the studio floating slab is thicker than 2.5 inches is that bad?
or is that the method you worked out for the best TL etc?
Thanks a million for your time steve, you have been a real champion!
kinda regards,
Govinda

[knightfly]

Thicker on the top leaf would be better, but before you do EITHER we need to talk about total sprung weight, and other alternatives for the rubber when using heavier, concrete floated slabs - here's one example -

http://www.kineticsnoise.com/arch/noise ... crete.html

And the REALLY serious version -

http://www.kineticsnoise.com/arch/noise/lsm.html

Download their PDF instruction sheets for more education in this area -

There are other companies that make similar products, this is just one of the better known ones... Steve

[Govinda]

Cool!!
So would I get a good result with a thin slab on the isolation matting?? as you mentioned previously?
I'm guessing that it would be better low end isolation on a thicker slab with springs?
Looks like I got a lot of engineering to sort out!!
It seems alot simpler on the matting, as there arent any presure points with all the weight of the room falling a bit more evenly onto these points?
thanks,
I have also been told that rubber stops springing after a certain amount of compression and can be rendered useless if not used carefully...and that it degenerates after a ceratain amount of years! Is this true?
I sure gotta a bit of planning before I can finish the engineering!
Thanks again!
Govinda