John Sayers' Recording Studio Design Forum

Hey Guys,

After reading Rod's book and following the threads on floating floors, It seems to me that if your not making a concrete floating floor it's just a useless one.
So due to high cost of it and beeing the owner of a concrete slab , i guess the best way to go for me is to not float.

If your still wondering why i decided not to float, well these threads and rod's (rod Gervais home recording studio build it like the pro's)book are the reasons:
viewtopic.php?t=8173
viewtopic.php?f=2&t=8134

So now i've put all the info of the threads and the book together for my situation, and made a drawing of it.

Now I still have some question?
Hopefully you guys can help me out on this one.

Now I have to point out that on the drawing on the left side is a concreteblock wall, but only 1/3 of the studiowalls are concrete blocks, the rest is 12inch thick concrete

1) I want to use a single wall construction due to width restriction in my basement, that's why i was opting for a RC channel on the outer walls( outer shell), do you guys think this is the best way to go? Or should redo the order in wich the materials are placed to get better results.

2) Due to a verry uneven slab, i have to use a leveling concrete, i talked to my concrete guy and he told me he uses kork beneath the leveling concrete to reduce contact noise.
Should i let the concrete guy put it there or leave it out. Benefit or not? I guess if I let him put it there it would be a little bit like a floating floor, but a bad one. So what would u guys do?

3) Is there anything you guys would do diffrently when you look at the drawing?

Thanks upfront for all the info and Help!!

Yup! But I'm just curious: Why did you think that you might need to float your floor? With a 30cm reinforced concrete slab on grade, you have really good isolation there already! You'd only need to float if there was something else very critical sharing the same slab, such as maybe heavy machinery next door, or something like that.

Anyway, here's another good reason to not float your floor: This is real laboratory test data of many different methods for floating. As you can see, very few of them work for low frequencies, and most of them actually make the isolation worse than without.
http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir802.pdf

That's a three-leaf wall! The concrete is leaf number 1, the single layer of drywall is leaf number 2, and the double layer of drywall is leaf number 3. That's a bad idea, and a waste of money. Forget about the single layer of drywall. You should only ever have two-leaf walls, never three-leaf.

You also do not need the RC at all. None of it. Your outer leaf is concrete, then there is an air gap, then your inner leaf wall has two layers of drywall on a stud frame, so the two leaves are already fully decoupled: there is no need to decouple them again with RC. That just wastes money, for no benefit. You ONLY need RC if you cannot decouple your leaves by any other method.

Also, 1/2" drywall is too thin: Use only 5/8" drywall. 1/2" is too thin, too light, and too flexible.

Yes! Redo it: Concrete outer leaf, air gap, stud frame, two layers of 5/8" drywall. That's it. That's all you need (plus fiberglass insulation in the air gap, of course). You don't need the RC, and you don't need the third leaf.

Not necessary, and VERY expensive. Yes, you do need the leveling concrete, but no, you do not need the cork. You are isolating your finish floor in any case, so there isn't any need to do that twice. And I'm skeptical that the cork would even work the way he thinks it will.

My question is: How much isolation do you need, and how much do you expect this plan will give you?

Also, what is the plan for the ceiling? And what are the plans for the doors, windows, HVAC system and electrical system? The entire room has to be done to the same level, so all of those should be taken into account at the same time. It doesn't make sense to build a wall for 60 dB isolation if your ceiling is only designed for 50 dB, or your door is only designed for 40, or if the HVAC system has no silencers.

So those are some things that you should taken into consideration, in addition to the floor and walls.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

You mention width restrtiction - I assume that the room dimensions are at a premium. So I would (and did for my own build) consider Johns inside-out wall design in order to save some real-estate, and simultaneaously provide space for treatment.
http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm (Click on the Tab "Walls & Ceilings")

_________________
Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

Hey Guys,
Sorrie for the late reply, have been really busy here.

Hey soundman, I modified my drawing to the way you intended.

But I'm serieously doubting if it will be enough isolation for my purpose, and this whill also awnser your question.

I want to build one control room where I mix at about 90 db, the other room(tracking/ rehersal) I'll be using for band practice, so A normal band would be around 110 at least.

I know I won't be able to stop all of the sound getting out, but i'm trying to stop most of it. Do you think about 80 db would be possible, or is this an impossible task?

I'll post a drawing of the ceiling soon. The design should be almost the same, because the ceiling is also concrete.
I'm working on it.

For now here is the modified drawing. I also added a layer of plaster to the concrete blocks. The blocks are verry raw of texture, and defenatly not airtight. So the plaster layer should help a lot there. On the second leaf/wall I added a layer of plywood, according to jhon sayer's construction manuel combining different materials and thickness should also be effective for isolation.

If you have time check it out, and feel free to comment guys!

Thanks upfront!

Why are you doubting? Your original plan used three layers of 1/2" drywall, for a total of 1.5". Now you are going to 3/4" + 5/8" + 1/2", for a total of 1.9". You are also eliminating the tiny air gaps, going from three leaf to two leaf, and adding a layer of plaster! What is there to be doubtful about with a wall that is so much better in every way? At a rough guess, that new design should be getting at least 10 dB better isolation than your original one, maybe even 15 dB better.

But I guess it would help if you could define that "purpose" that you mention...

This diagram might help you to understand how much you have improved your isolation by making those changes:


Your original design was something like the example in the middle. Your new design is very much like the one on the right. ...

Your estimates sound about right. The best level to mix at is not more than 85 dB, except for brief higher levels to check specific things. Control rooms should be calibrated at 85 dB, and you don't damage your ears too much mixing all day at 85.

It's not easy to say exactly how much isolation that you'd get from your proposed new method, but theoretically it should be in the high 60's, maybe even getting to 70. That is very, very good. For example, with 65 dB of isolation, your 90 dB mixing would be totally inaudible outside the room, and your 110 dB rehearsal would be slightly audible just outside the wall, and practically inaudible a few meters away. You probably won't be able to get better than that, since you will be restricted by the flanking limit of the concrete floor, plus all of the other details that limit the maximum achievable isolation.

80 dB of isolation will take a lot more than that, and it is highly unlikely that you need 80 dB of isolation anyway. 80 dB of isolation would make both your mixing and your rehearsal totally inaudible right on the other side of that wall. Why do you need to do that? Most sound level meters would not even be able to measure such a low level, so you'd never know if you achieved it or not (most low-cost meters can't read below about 40 dB or so).

Most people here are happy to get 50 dB of isolation, very happy to get 60 dB, and on their knees, crying in ecstatic thankfulness if they get 70 dB. And you want to go ten times better than that? Why do you need such a high level?

Even if you can get your walls built to isolate to 80 dB, the floor and ceiling will not get to that level with your current plan. You will definitely have to float a thick, massive concrete floor on isolation shock mounts to do that. Or dig out the existing concrete slab and pour a new one on a separate foundation, isolated from the existing foundation. Then you'd have the problems of doors and windows. Getting doors to isolate to 80 dB is a big issue: you are talking about doors that weight hundreds of kilograms, multiple seals, and very large air gaps. And finally, your HVAC system will have to be double-isolated, with some rather complex silencers, to achieve that type of isolation.

Anyway, to answer your question: It is not an impossible task, and can be done, but it is going to be very, very expensive. The very best isolated studio in the world (Galaxy), gets about 100 dB of isolation, but required millions of dollars to build, and some of the best acousticians in the world to design, so it can be done. But it is not cheap, and not easy.

Yes, the plaster is a very good idea, and definitely will help. Plastering the other side of the blocks MIGHT help a little bit more, but it would only give you about 1 or 2 dB extra. However, if you really are aiming for 80 dB of isolation, then you will have to do everything possible to achieve that.

The 3/4" wood is an excellent idea, but it should be the FIRST layer on the leaf, attached directly to the studs. Then you can put other layers on top of that. Also, I would use two layers of 5/8" drywall there, instead of one 5/8" and one 1/2". You need the extra mass to get to the very high levels of isolation that you are talking about. I would also use 2x6 framing at 24" OC, instead of 2x4 at 16" OC, in order to slightly improve low frequency isolation. You should also use Green Glue between the layers, to increase low frequency isolation even more.

I guess the real issue here is why you think you need such extreme levels of isolation. Maybe you really don't need 80 dB of isolation. I sure hope you can live with a lower level, since getting up to 80 dB is going to be very, very expensive for you, and very hard to do.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hey Stuart,

Ok I learned my lesson, I'll have to be satisfied with the 60 or 70 db isolation, 80 is a defenatly out of my league!

My purpose was to just not disturb the wife and kids, in september i'm expecting a new born. so no noise in the house ya know.
I also play late into the night, but that's just around the 85/ 90 db. So this type of construction should give me fairly enough isolation and serves my purpose.

So my main concern whill be the ceiling(where the wife and kids are at). I'll post a design drawing soon, so you can have a look.

Here is the updated wall design.



Stuart I'm still wondering? According to Jhon's manual I should put the board between the sheets. But there is a difference, he speaks of a fibre board instead of plywood.
Should i maybe combine the 2? plywood/ sheet / fiberboard / sheet?
Or would this just be a loss of money again.

Thanks for all the effort and support!

greets

Nillis

Exactly: That's for an entire different reason. If I'm not wrong, that's the way John used to do it, many years ago, but as far as I know, he no loner does it that way. And plywood is not fiberboard!

The reason for putting the plywood on first is structural. If the plywood is directly on the studs, then the wall is very strong in sheer (stresses in the plane of the wall itself, trying to collapse it). But if you put drywall first, then plywood, you lose that. Also, plywood on the studs gives you a major advantage later on: you have a nailing surface around the entire room! so you an hang acoustic treatment anywhere at all, not just where the studs are. Big advantage.

There is also no need to use different thicknesses of materials in the wall "sandwich": Yes, it does give you a slight benefit from the differing coincidence dips, plus refraction from the differing impedances, but the effect is offset by not having maximum mass and thickness. If you use a sheet of 1/2" drywall wher eyou could have used a sheet of 5/8", then you have lost that extra 1/8" thickness, and the associated higher rigidity, and the associated mass. You gain more than you lose by going with thicker, more massive, more rigid materials.

Don't forget that John wrote that manual a long time ago, and has since changed his mind on a few points. I'm not sure if this is one of them, but I suspect it might be!

You could, but I would suggest that a better plan would be "plywood - drywall - Green Glue - drywall". The Green Glue is a visco-elastic polymer that acts as constrained layer damping, and provides a lot of extra isolation in the low frequencies (drums, bass, keyboards, etc.). It would be more effective than the fiberboard for that.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hey Stuart,

Good point there with the order for the plywood!and the Mass. I guess Jhon would have to follow you there!

I've already heard a lot about the green glue, but I haven't been able to find it here in Belgium.
I'll look around for it some more, it's going to be a must have for the build.

I just updated my drawing. tell me what ya think.

I opted for a independant ceiling in the drawing. Seems to me the easiest and cheapest construction method.
I have been re reading rod's book on this, but construction in the U.S. is verry diffrent then here.
Rod's book only writes of wooden ceilings/ floor for the residents. Out here it's concrete.
So I guess if I build the ceiling almost the same way as the wall it whill be enough.

I'll try to post a close up view of the wall ceiling connection. In rod's book he speaks of a firestop, I'll have to go a little deeper on that part.
Seems to me there isn't a easy way to build this. There is always contact between wall/ceiling with the outer shell. so vibes go through.
Thats deffenatly a no go.

I was still wondering, where the stud of the ceiling rests on the stud from the wall, should i put some sort of neoprene or isolater between them?

The same question goes for the wall to concrete slab attachment.

greets

Nillis

Looking MUCH better!

Yup!

Just one word of caution: for the ceiling joists, 2x6 might not be enough. ("Joists" is the technical name for "studs" in the ceiling) You should calculate the dimensions of those joists based on the load and the span. That's a heavy load, and 2x6 cannot span a long distance with such a heavy load.

That's not necessary. The entire inner leaf all works together, so it can all be connected solidly, if you want. The most important things is that the inner leaf cannot touch the outer leaf.

Also not necessary, since you still have to put nails or bolts through the sole plates, rubber and into the floor, in order to hold the wall in place. That creates a solid mechanical link, which bypasses the rubber: vibrations will just travel along the nail or bolt directly. There are some systems that completely isolate the wall, by putting special isolation collars around the bolts too, and you could consider those if you really want to maximize every last decibel of isolation. It might gain you a couple of dB, but it is more expensive and complicated to do that.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hey Stuart,

I took some pictures of the basement. so you can check it out.

About the load of the ceiling, i'm not sure how to calculate this? I suppose i should ask the wood supplier for the weight of the stud, the load the studs can bear and under what span.

If you check the pics, the max span of 1 stud would only be maximum 14 feet. I guess this is not that much for a 2X6 stud.

I'm going to need some help on calculating this dude!

Also had another question about the air gap betwen the outer leaf and inner wall. How many inches should this be?

Thanks dude!
enjoy the wekend.

I'm not a structural engineer, and I don't know your local building codes or the types of wood you can get locally, so I can't really calculate this for you. There are on-line span tables that might help you to get an idea, but you'll need to know things like live load, dead load, deflection, joist spacing, type of wood that your joists are made of, etc. It would probably be advisable to get a structural engineer to do this for you. I do know that you can't span 14 feet with that kind of load, low deflections, and 24"OC spacing, with some types of wood, but you might be able to with other types. Or you might need to move up to 2x8, or move down to 16"OC, or even 12"OC. But once again, call a local structural engineer and find out what is permitted in your area, what type of wood is available, and get his OK on it.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hey stuart,

I'll contact them for the load!

Thanks for all your time!

I'm currently working hard on my studio layout so I whil be posting in the design section.

When I'm done there, I'll be back for more enlightment!

Thanks upfront dude!

Hey Stuart,

Finally got my first design done.

If you have the time you can check it out here:
viewtopic.php?f=1&t=17722

I could really use your expert insight!

Thanks hombre!