Building a house above my studio in Ecuador

I have a sort of unique situation that I have not been able to find in the forums, though there are likely many precedents. Rather than building a studio that shares walls or floors/ceilings with an existing residential space, I am embarking to build a residential space that shares a floor/ceiling with an existing studio. Some five years ago I embarked on a long process of building a recording studio. At the time isolation was not a huge concern because the construction was relatively far away from the closest building, which is my inlaw’s house. I instead focused most of my energy on acoustics and built two rooms I have been very proud of. I now have a baby on the way and it is no longer going to be tenable to continue to live with my inlaws, and I plan to build my house on top of (as well as flanking) the studio. The current construction is built out of sand filled cinder block walls that are plastered on both sides, as well as painted with two impermeable coats and two regular coats of paint (on both sides). The roof is a concrete slab consisting of rebar, 8” cinder block, and cement. The cinder blocks are not sand filled, but because it is a filled slab the total thickness is slightly more than that of the plastered walls. I have noticed that flanking is a huge problem with these concrete slabs. For example, the sound of my dogs’ fingernails on the slab above is amplified. Rather than adding to the inside roof of the studio, I plan to float a floor above the studio to minimize flanking sounds from the house, as well as provide isolation from the studio. How much isolation? I’d like as much isolation as possible. The studio is often a place where very loud things happen, and I will soon have a newborn trying to sleep upstairs. I don’t really have much experience as to how much noise you can get away with around babies. I do understand that you cannot isolate only one surface and I intend to bulk up the walls below as well, but first order of business: My plan is to float the floor of the house. I plan to do this by floating studs on neoprene pucks with two layers of plywood sheets on top with fiberglass in the cavity. In some of the house there will be hardwood floors (or parquet) on top of the plywood and in the bathroom there will be cement and tile. There is a company here that can manufacture neoprene pucks at the thickness and durometer that I specify. Additionally, they say that they can help me determine what will be optimum for 10-20% compression under the load of the house. In Recording Studio Construction, Newell suggests separate spring systems for the walls as compared to the floors so as to avoid the “crown effect,” as well as serving to optimize the compression under different loads. As such I have calculated the weight of the walls per longitudinal meter. I also need to figure out how to determine the total weight of the roof and divide it by the perimeter so that I can add this weight as well. Another issue is that the floor will not present uniform loads, for example the bathroom will weigh considerably more than the bedroom. Would this mean using different thicknesses and durometers of pucks as well? There are 855.8 lbs of cement for every longitudinal meter (that is to say that this figure already sums the weight for the given height of the walls). There are 44 Ecuadorian bricks (which total to 660lbs) for every longitudinal meter. How often do I place the pucks? Every meter? Given this amount of weight should I increase the thickness or durometer (from ½”, 60 durometer)? Now, what if I simply did not decouple the walls? Would flanking prove to be too much of a problem? I’m also looking into other options such as increasing the mass of the slab by adding sand, and have a structural engineer coming by in a day or two to tell me what I can do safely. Ah, and of course, rule number 7 (don’t tell us you want to float your floor)… The structural engineer said it would be fine. Does this rule just apply to floated concrete slabs or does it include the type I intend to do? It seems there are a lot of cases of people doing this? This forum is really an impressive resource. Thanks to all of you for sharing your experiences.

I was curious about exactly how much cement was in the roof slab. It turns out there is quite a bit more than a cinder block wall with plaster on both sides. In total the slab is 20cm thick. Oh also, my apologies if I sometimes use metric and sometimes use imperial. Ecuador is kind of weird like that. :D

Hi there "studioilalo", and welcome to the forum! :) Your situation certainly is a little "backwards" from normal! But the same principles still apply, so it's just a matter o using them for a house, not a studio.

My plan is to float the floor of the house. I plan to do this by floating studs on neoprene pucks with two layers of plywood sheets on top with fiberglass in the cavity.

Unfortunately, that won't work. It's a common misconception that you can float a light-weight floor like that on rubber pucks: in reality, all you succeed in doing is building a rather effective resonant chamber. Despite what you see all over YouTube and even on some "acoustic" web sites) , this is not the correct way of doing things. Here's why:

http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=8173

Basically, the issue is simple: you need enough mass and the right spring to make the MSM resonant frequency at least 1.414 times lower than the lowest frequency that you need to isolate. In reality, it should be twice as low, or lower. It simply is not possible to get enough mass from a few sheets of wood. If you want to understand the technical reasons, and to compare many laboratory-tested methods for floating floors, then take a look at this document:

http://archive.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir802/ir802.pdf

There is a company here that can manufacture neoprene pucks at the thickness and durometer that I specify.

Rubber is fine for some frequencies, but not for very low frequencies Lows usually need springs. These are the type of springs you normally use for floating floors: Here's how it is normally done: I'm not even convinced in the least that you need to float anything: Rather, you simply need to isolate your new house from the existing studio. That's the goal. And it very likely can be accomplished without going to all the expense of floating walls or floors. Why do you think you need to float your floor? That's the question. What is wrong with the ground that makes you think there will be a problem? If you pour your house foundations separate from the existing studio foundations, and keep the two isolated from each other, I don't see the reason why you would need to float anything. You would only need to float if there is some very large problem with the ground that would cause transmission from the studio foundations to your house foundations. Your first priority should be to figure that out.

I also need to figure out how to determine the total weight of the roof and divide it by the perimeter so that I can add this weight as well. ... Another issue is that the floor will not present uniform loads, ... Would this mean using different thicknesses and durometers of pucks as well?... How often do I place the pucks? Every meter? ... should I increase the thickness or durometer (from ½”, 60 durometer)?...

Exactly! :) Those are, indeed, some of the many, many questions you will need to ask, and answer accurately, in order to float a floor. And if you get the answer wrong for even ONE SINGLE PUCK, then you are screwed. If one single puck bottoms out because there is too much load on it, then the entire building stops floating, and you wasted a huge amount of money, time and effort. That's the issue with floating a building (or a wall, or a floor). There is only way way to get it right, and an infinite number of ways of getting it wrong. So your chances are not too good.

Now, what if I simply did not decouple the walls? Would flanking prove to be too much of a problem?

Now what if you didn't float the walls OR the floor? Would flanking prove to be too much of a problem? :) That's the question you should be asking. That takes me back to my other question: why do you think you need to float your house? What tests have you done in the ground around your existing studio to determine if you even have a flanking problem? You seem to be concentrating on inventing a very complex, very expensive solution to a problem that might not even exist. It would be better to first concentrate on determining if there is a problem with the ground where you plan to build your house, and if so, what the magnitude of that problem is. I suspect that the ground doesn't have any problem at all, and that a more conventional (and cheaper!) solution would be the best.

I’m also looking into other options such as increasing the mass of the slab by adding sand, and have a structural engineer coming by in a day or two to tell me what I can do safely.

wait a sec: you said you were going to build your house around the studio: you said that there is no slab for the house yet. So I don't understand what you are talking about here, with "increasing the mass of the slab by adding sand". Maybe you could explain? I'm thinking that there is a basic misconception of the principles of isolation here: maybe you can post some photos of the existing studio, from the outside and inside, so we can see what you have, and help you figure out where to go, based on that?

Oh also, my apologies if I sometimes use metric and sometimes use imperial. Ecuador is kind of weird like that.

Chile too! :) No problem: most people here are "bi-lingual" with both metric and imperial measurements, so just use whichever fits best. Another question you need to answer urgently: How much isolation are you getting right now? Test that with a sound level meter (C-weighting, slow response) - Stuart -

Thank you for your reply! First I'll clarify: Most of the house is going on top of the existing studio. I think I caused the confusion by calling the roof of the studio the slab. I'm not sure what its called. Its a concrete roof made of rebar, cinderblocks and cement. Its 20cm thick. After reading your post I realized what I had glossed over in Newell's description of the resonant frequency of floating floors was the mass of the floor being floated. I spent all my time thinking about the tension of the spring. Of course, this makes perfect sense. Also your suggestion to determine how much isolation there already is spot on. I'm going to get a spl meter tomorrow and do some thorough tests and post the results here. Thanks again!

Right! :) I'd suggest that you plan this as building a "room around a room", sort of the opposite of "room within a room". Just so separate foundations for the house, not connected at all to the studio foundations, perhaps even with pillars in some places to support the upper level, and leave the studio just as it is. The house and studio must not touch each other at all: leave a few inches of air gap between them, and fill that with fiberglass or mineral wool insulation. That will give you pretty good isolation, if you build the new place with concrete floors and walls too, like the studio. When you have your meter, set it to "C" and "Slow", then get the loudest possible session going inside your room, very bass-heavy, and hopefully hitting around 115 dB as measured inside the room. Then go outside, close all the doors tightly, and measure the level in several places around the studio. First at about 1 meter away from each wall, then again at about 8 m away from each wall. Measure other locations too. If there is some way you can get up above the roof, then measure up there too. Note them all down, and post them here. - Stuart -