After reading Rods book and many of the posts here, it seems that the concensus is not to either sawcut my garage slab, nor float a floor over it to isolate my room. The intent of my room is to be a jam space / rehearsal room for myself, my kids and for my band (late at night sometimes when the kids are sleeping). Note that we tend to play hard rock / alt rock so volume and bass are issues I need to deal with.
My garage is attached to the house via footing and slab on grade, with 2 kids bedrooms directly above. Also, the water table is very high where I am, Richmond BC, so sawcutting the slab, weighing it down and vibrating it would eventually cause the ground below to go into a state of liquifaction.
My idea for the floor is to place my inner leaf of the MAM wall on a continuous NEOPRENE or EPDM pad the width of the plate (any comments on your preference) between 1/2 inch to 1 inch thick directly on the garage slab (I found a great source in Vancouver for all types of rubber, etc. at contractors pricing). Any comments on the hardness as they have several to choose from.
Then, once the walls are framed up, place a thinner neoprene or EPDM rubber sheet, maybe about 1/8 to 1/4 inch thick over the existing garage slab and wrap it up about 2 inches up the framed walls.
Then pour 1-1/2 to 3 inches of concrete within the room over the sheet. The purpose would be 2 fold. Firstly, to create isolation and secondly to level the floor (the garage floor is sloped).
I found someone that specializes in specialty concrete products and has a concrete product that is self leveling 42 MPA and has no aggregate base (which to me would seem to increase the problem of sound transfer). The concrete has a gypsum and silica sand base with a weight of about 115 lbs/ft^3 (I believe regular concrete is approx 150 lbs/ft^3). The product comes in bags and he has a machine that he pulls behind his pickup truck and pumps it using a 3/4" hose. He is researching the acoustical properties of the concrete. It is more expensive than regular concrete but it's through a friend so I hope to get a deal.
Any advice, comments or criticisms would be greatly appreciated.
Thanks in advance.
Danny
What do you think of this floor detail ?
Originally posted at johnlsayers.com, topic 11739.
Hi Danny, and welcome!
Floating your walls (which is what you are describing) is the same as floating your floor, in the sense that you still have to do all the calculations to get it right, or not bother doing it at all. You will need to know the total mass that you will be floating on those pads, which in your case is the mass of the walls, doors, windows, and inner-leaf ceiling, plus the acoustic treatment that you plan to use, or rather, the acoustic treatment that will be attached to walls/ceiling. Your calculation of this total needs to be fairly accurate, to with a few percent. You also need to calculate if the load is going to be spread evenly across all the bottom plates, or whether your walls will be heavier in some areas than in others (for example, a Rod "superdoor" is very heavy, so that section will need to be floated differently). If you have some sections that are loaded more heavily than others, you need to figure out how to handle that: different type of rubber? Spread over more area? Etc. Then you will need to know the manufacturer's technical specifications of the specific type of neoprene / rubber / EPDM / whatever that you plan to use for this floating. Specifically, you need to know the manufacturers specs for the mass loading that will cause the material to compress correctly to obtain floating. That depends entirely on the specific material that you select. Every manufacturer and product line has different specs. You can't just guess what it might be! You need to find out for certain, from the manufacturer. Now, if your calculations are wrong (or if you don't bother doing them), then there are three possibilities: 1) Your wall will be too heavy, and will over-compress the neoprene, in which case it will not actually be floated at all, and you will therefore have wasted a huge amount of time, money and effort in a pointless exercise: if this is the case, then the rubber will be "bottomed out", the wall is not floating, and you have a direct flanking path from wall to slab. 2) Your wall will be too light, and will not compress the neoprene at all, in which case it will not actually be floated at all, and you will therefore have wasted a huge amount of time, money and effort in a pointless exercise: if this is the case, then the rubber will be "topped out", the wall is not floating, and you have a direct flanking path from wall to slab. 3) By some incredible stroke of good fortune, you just happened to guess right, and the neoprene actually is compressed the exact right amount. The odds of this happening by chance are pretty much the same as the odds of you winning the lottery and getting struck by lightning in the same day! In other words, this is not something you can just do by sticking some bits of rubber under your bottom plate, and expect that, by sheer luck, you will get the exact correct loading on the rubber to compress it to the perfect point where the wall actually does float. If you really do want to do what you have in mind, then you absolutely must do the math and make sure you get it right. If not, you are wasting your time, money, and a nice chunk of rubber that might be useful to someone else, rather than sitting uselessly under your wall fully compressed, or not compressed at all.... .) Summary: It can be done, but the math is not simple, and any error in calculation or installation makes it all useless.My idea for the floor is to place my inner leaf of the MAM wall on a continuous NEOPRENE or EPDM pad the width of the plate (any comments on your preference) between 1/2 inch to 1 inch thick directly on the garage slab (I found a great source in Vancouver for all types of rubber, etc. at contractors pricing). Any comments on the hardness as they have several to choose from.
The "hardness" has to be the exact correct hardness for your exact wall loading. No more, no less. The manufacturer should be able to tell you how much each type needs to be compressed in order act as a spring, and that will probably by in terms of percentage under load. So for example, you will be able to figure out that the correct range for your specific type of rubber / neoprene / EDPM / whatever is a load of X to Y kilograms per square cm, which will compress the material at least G% and not more than H%. If you have less than X kg/cm2 loading, then you are not compressing it enough, so it is not floating your wall. If you have more then Y kg/cm2, then you are over-compressing, and thus not floating. Either way, if it is not floating, then it is flanking just as certainly as if you glued and bolted it directly to the slab, without anything in between.Any comments on the hardness as they have several to choose from.
Once again, that basically IS floating your floor! If the "EPDM rubber sheet" is not compressed to the correct range, then it will not float, and will flank instead. It will be as though it was not there, and you had just laid concrete on concrete. So once again you will have wasted a lot of time and money. Except that this case is more complex, since you have both live load and dead load to consider. In the case of a floor, you will have people, furniture, and equipment loads changing all the time, as you come and go. You need to make sure that even with the minimum load the EDPM is compressed enough to float, and even with the maximum possible load (the room full of people, amps, furniture, and beer), then the EDPM is not over-compressed. As you can imagine, it is rather more complex to get these calculations right for a varying dynamic load, than for the "simple" static load of the walls...... place a thinner neoprene or EPDM rubber sheet, maybe about 1/8 to 1/4 inch thick over the existing garage slab and wrap it up about 2 inches up the framed walls. ... Then pour 1-1/2 to 3 inches of concrete within the room over the sheet.
I'm not sure I understand that reasoning: Why would the lack of "aggregate base" increase transmission loss through the slab? I'm not trying to say that you should not do what you propose: I'm merely pointing out that is is far more complex than you seem to have taken into account, that you need to do some rather complex math here to get it right, and that failing to get the math right (or not bothering to do it and just hoping that the laws of physics will take a vacation in your neighborhood of the universe while your studio exists), has an extremely high probability of resulting in a wall or floor that actually is NOT floated at all. And if it is not floating, then it is flanking. Your chances of it turning out right by sheer fluke are very, very slim. If the material is not compressed just right, then the final result is just as if it were not there at all, and the wall /or floor) was directly attached to the slab. - Stuart -... has no aggregate base (which to me would seem to increase the problem of sound transfer)
Hi Stuart:
Thanks for the quick and detailed reply. My thinking was that I am placing my room on a 45 year old concrete slab that has hasn't cracked to date and is about as hard as it will ever get. By placing the rubber between the wall and slab and also between the slab and new concrete to cause the same damping effect much as I hope to achieve by placing the Green Glue between the sheets of drywall on my wall... but in reality I guess that my thinking is actually a floating floor. How much of the vibration from the band instruments will actually transfer through the slab to the footing and foundation and then through the superstructure (wood framing) of the house to the second floor and affect the occupants, and if so to what degree does this typically happen based on your experiences out there.
As for the concrete aggregate, I take the example Rod gives in the book of hitting a 2x4 at one end with your ear touching the other end, except looking at doing that with a rock. I would guess that the rock would transfer the vibration from one end to the other almost perfectly due to its "hardness" or compactness of its molecules. If the concrete contained silica sand and gypsum (which would not have the hardness of the stone aggregate used in concrete) , essentialy very tiny pieces of rock, that there would be some energy dissipation as the vibration energy had to transfer from one small piece of rock (i.e. piece of sand) to the next until in made it to the other side of the slab, therefore a reduced amount of vibration "energy" would make it through to the other side of the slab (sorry, but that's my brain working with my engineer's cap on, I just wished I had studied some acoustical engineering at the time). Do you think that a lightweight air-entrained concrete (typically used in woodframe residential construction, no strength to it) work better.
As my main concern is bass drums, bass guitar and the likes of that affecting the occupants on the interior of the house late at night during practice, do you think I am better off building up mass on the existing floor with plywood, gyproc, etc. or even placing a 2" - 3" concrete skim coat directly over the slab to level it, rather than "floating a concrete floor" (doing the calcs shouldn't be too much of a problem for me). Would I gain any or a significant benefit from floating the floor I originally described assuming that I did the calcs right and had compressed the rubber correctly. Further to this is it worth investing in those spring devices that you cast in your floor and then lift them to float your floor. My worry is not perfect recording room acoustics, but rather, well, "...turn that %$&%$# noise down, your shaking the house apart and we're trying to sleep" !!!
Thanks again,
Danny
Hey Danny.
Have you done any actual measurements in your room / house, with a sound level meter? Without that, it's hard to say what you need / don't need to do. I'd suggest that you set up your drum kit where you normally play it, get a heavy-handed drummer to whack out a really loud song, just as hard as he possibly can, over and over again, while you take detailed measurements. First, measure the levels right there, in the room, next to the kit. Then go out of the room, close all the doors and windows, and measure in several places just outside the room. Then take further measurements in the various rooms from which those comments on your playing skills normally come(!). Then repeat all of the above WITHOUT anyone playing the drums (or anything else) in that room, just at normal average household noise levels, so that you also have an ambient baseline against which to measure and design.
Set your meter on "C" weighting, and long integration, and take several measurements of both peak and average readings. If you can get a meter like the Phonic PAA3 that gives you full spectrum 1/3 octave readings, then that would be great, but if you only have a simple meter, that will do just fine too.
This will give you some real numbers to work with. Now you will now how loud you are at peak volume, and how quite you need to get that in order for the "encouraging" comments from your family to disappear. This is the number that you need to aim for in designing your isolation. You can't just guess your way to the right construction technique for your house!
As an engineer, you already know that you the laws of physics are inviolate, and can't be changed by wishing them away, so you know that the only way to do this right is "by the numbers". And starting with those "big" real numbers in mind, you'll be able to design the real isolation that you will really need to get to the "small" real numbers that your family desperately wants.
It's as easy as that! ( :) )
What you describe is called "flanking" noise, or the noise that goes around the edges of your isolation strategy. Once again, the amount of that that YOU will get, depends on YOUR specific structure. How thick is the slab? How is the rest of the house built? Etc. You can't rely on other people's cases to determine if you have a flanking issue or not: you need to determine if YOUR specific house has an issue or not. Here is a link to understanding what flanking noise is, and common methods for dealing with it. http://www.greengluecompany.com/underst ... gNoise.php - Stuart -How much of the vibration from the band instruments will actually transfer through the slab to the footing and foundation and then through the superstructure (wood framing) of the house to the second floor and affect the occupants, and if so to what degree does this typically happen