Basement studio construction has begun...

I am finally moving a thread I had in the Studio Design category over to the construction category. That in and of itself is a great accomplishment! :-) http://www.johnlsayers.com/phpBB2/viewtopic.php?f=1&t=16112 My first question is this: As part of this project we are finishing our entire basement. We have a contractor doing the work for the rest of the basement and I was intending to do the majority of the labor on the studio. As part of this process, the contractor framed up the walls/door that lead from the larger basement area to the CR and the Tracking room. In addition, the contractor thinking he was being helpful, framed out a thin wall against the back solid concrete basement walls. They ripped 2x4's in a half lengthwise. So essentially the 2 walls of the tracking room are framed using 1x2. The big question is, since this is against a solid poured concrete wall, is that really a problem? Do I have them rip it out and re-frame with 2x4's? OR can I use it as is. There is about a 2 inch gap between the framing and the concrete wall, so I could but a good amount of insulation in there. Thoughts? Advice? Thanks! Eric

Ok, you know a lot about this project, but most of use do not keep up as well :) I read that you say "back" wall, and wonder which wall this is? If it is an existing concrete wall, and your guy has furred it out on one or both sides, this is not where you want to go. Mass is better placed in such a way as to continue to be mass in an unbroken fashion. Any alteration as in a furring that attempts to get more air but in reality only couples...is useless. But I do admit I am having trouble getting into what you are saying versus what was really installed, and frankly, at what wall and where in this room this happened.

the contractor thinking he was being helpful, framed out a thin wall against the back solid concrete basement walls. They ripped 2x4's in a half lengthwise. So essentially the 2 walls of the tracking room are framed using 1x2.

Like Brien said: you don't want to go that way. If you put drywall on that, the entire wall will be a panel resonator, tuned to a specific frequency, which most likely will not coincide with any useful frequency for your room. Putting absorption in the cavity will only achieve broadening and flattening the Q of the panel trap (making it affect a few more frequencies, a bit less efficiently). - Stuart -

Sorry for the vague description. I am including some pics here to help explain. Also, I am planning on building double walls inside of this framing that was done. Do I need the double walls against a solid poured concrete walls or if I redo what is there with standard 2x4 walls, will that be enough for those walls? Thanks for the comments.

Also, I just took measurements of the the walls as they are now and I am concerned about the dimensions of the CR. It is getting rather close to a square and that as we all know is no good. The bottom of the floor joists above to the concrete floor is 9ft. The room dimensions are 11ft10in x 12ft8in. Obviously those will change as I build the inner walls, but my concern is that the ratio will not change dramatically if at all. Should I adjust the inner walls to modify the ratio a bit? Thanks again for the advice.

I am planning on building double walls inside of this framing that was done.

Why? :) You don't need double walls INSIDE the framing: the framing itself is part of the double walls! Just put drywall on only ONE side of that framing, and you have your outer leaf. Then build only one more frame about an inch away from that, and put drywall on only one side of that framing too. That will be your inner leaf. Nothing more is needed. Of course, the inner leaf framing cannot touch any part of the outer-leaf framing, or the existing walls or ceiling.

Do I need the double walls against a solid poured concrete walls or if I redo what is there with standard 2x4 walls, will that be enough for those walls?

Once again, the concrete wall IS your outer leaf, and the framing next to it COULD be usable as the inner leaf, PROVIDED THAT IT DOES NOT TOUCH THE CONCRETE WALL. From the photo "Framing-2.jpg" it looks like there might be an air gap between the framing and the concrete. If so, and if that framing rests ONLY on the floor with no attachment at all to the concrete wall, or to the floor joists above (not even a single nail), then you are fine, and you can use that framing for your inner leaf. If not, then you can either take that framing out and re-build it an inch or two away from the wall (not touching), or leave it there and build another frame an inch away from it (not touching).

The room dimensions are 11ft10in x 12ft8in. Obviously those will change as I build the inner walls, but my concern is that the ratio will not change dramatically if at all. Should I adjust the inner walls to modify the ratio a bit?

Your final inner-leaf dimensions will be around 11'11" x 10'10" x 8'6", which is not a bad ratio at all! Very close to Sepmeyer's first two ratios. I wouldn't sweat it too much. - Stuart -

Thanks Stuart! I think I understand your dimension calculations. As far as the walls, you are taking in to account the inner 2x4 walls and an air gap between inner and outer. As far as the ceiling, where does that come from? I could see 2" or so on the low end or even 6" or 8" on the high end. How are you calculating the 4"? Just want to make sure I am on the right path here. THANKS!

If you are working with a known ratio you have to know that the dimension is according to the interior finished hard boundary. In other words, when you measure this room, you measure to the hard boundaries not the framing, to get the ratios. True that ratios are only a means to keep us from building square or cubed rooms and aid in making a more balanced and even room in respect to acoustical response, and there is tolerance in the suggested ratios but as Trevor Cox has shown even those ratios can be modified...Eric Desart suggested the same thing with graphs even before Professor Cox did.

As far as the ceiling, where does that come from? I could see 2" or so on the low end or even 6" or 8" on the high end. How are you calculating the 4"?

6", not 4"! :) You said you had 9 feet, I suggested that could come down as low as 8'6". Let me explain: You originally said:

The bottom of the floor joists above to the concrete floor is 9ft.

So I allowed 6" for your joists, your drywall, and a bit of clearance under the joists. You didn't mention angling your ceiling, nor did you mention if it is possible to interleave the new inner-leaf joists with the existing outer-leaf joists, nor if you are thinking of building inside-out. So I assumed the worst case: Plain rectangular room, built normally with no interleave. If you can interleave, or if you do decide to build inside-out, then your ratio could be adjusted. But if you angle the ceiling, then this entire discussion is a moot point, since angling the ceiling means that you can no longer use the simple equations for rectangular rooms. As soon as you angle a wall or the ceiling, the room is no longer rectangular, so the equations do not apply any more. Modal behavior for non-rectangular rooms is rather more complex to predict.

As far as the walls, you are taking in to account the inner 2x4 walls and an air gap between inner and outer.

Correct. Once again, I'm assuming average case: a couple of layers of drywall on 2x4 studs, plus a gap between the studs and the existing wall. So I allowed 6" for each side of the room, thus reducing length and breadth by a foot. But I screwed up when I wrote that! :oops: It should have been (of course!) 11'8" x 10'10" x 8'6" (rather than 11'11" x 10'10" x 8'6"). Finger fumble.... :oops: So you'd lose a foot of length, a foot of width, and 6" of height. That's just a rough estimate, based on typical average isolation techniques, for typical average isolation requirements. It might be different if, for example, you decide to splay your walls, angle your ceiling, build inside out, use exotic materials, or if you have unusual requirements. And as Brien also pointed out, ratios are not written in stone, and are not magical. All they do is to help to even out your modal distribution, nothing more. Getting away from the bad ones and reasonably close to a good one, is plenty good enough. - Stuart -