John Sayers' Recording Studio Design Forum

I'm currently working with a builder on a design for a partial garage conversion for a drum practice/teaching studio. Thanks to this site (I think my eyesight has deteriorated significantly reading it over the past couple of months...) I think I've managed to tackle the question of wall design fairly well.

Two external walls will be 1 leaf of brick/concrete block with an air gap and second leaf comprised of a stud wall with double plasterboard on the inside. The other two walls will be of double stud construction, double plasterboard on the outside and inside (different thicknesses on one side) with a significant airgap to help with Low Freq. Tran... MSM construction all the way, and enough acoustic caulk to gag an elephant. All seems good.

Now comes the ceiling... The garage has existing timber framing at a height of 8' and and an angled roof that peaks at around twice that height. I'm considering simply adding two layers of plasterboard on the underside of the existing framework along with Rockwool Acoustic Slab above that. Should I be considering resilient channel in the ceiling? Am I going to gain a significant enough amount of transmission loss to justify it in such a situation? I notice that there are ceiling designs mentioned on this site both with RC and without. Can anyone pitch in their 2 pence on this one?

Well, I am no expert, but I am just going on what I have been advised and read about. I went with RC on a small part of a ceiling that I could not afford to lose any more height by creating a free-floating frame.

Your isolation is only going to be as good as your weakest link. You could have solid lead walls that are 10 feet thick, and then if your ceiling is compromised, you might as well have not bothered with the walls.

There were several times with my build where I started to take a shortcut somewhere, but then I was brought back to reality with the "weakest link" issue. If you have a big hole in your isolation, all of your other work is for naught.

My advise, get the RC and do not skimp ANYWHERE!

Good luck!

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James

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"Never interrupt your enemy when he is making a mistake."
Napoleon Bonaparte

Fair enough. That's the way I was leaning, for exactly the reasons you stated. My detracting thought is that since there will be a minimum 6" and maximum 6-7 foot air gap between the "new" ceiling and the existing tiled roof (second leaf) that I wouldn't be gaining THAT much by hanging the new inner ceiling on RC. I suppose in the end the cost isn't that much different and I will - at the very least - gain some TL in the mids and highs; which in my case means snare drums and cymbals.

In order of VAlue - greatest isolation to least isolation:

Independant ceiling

RSIC clips

RC-1 or 2 (I reccomend 2 for ceilings)

Direct connect.

Walls would be the same - If the ceiling has RC-1 clips then that is your weakest link - and will do a lot to determine your over all isolation value/

I wsould reccomend that you try to figure out a way to do an independant ceiling - and then opt for RSIC clips if that is not possible.

Sincerely,

Rod

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Ignore the man behind the curtain........

Thanks Rod. (Got a lot of mileage out of your book, BTW...)

I've considered an independent ceiling, but because the existing timber framing is at 8", I prefer not to cut into my headroom another 6 inches, though if the performance were to be significantly better, I suppose I'd have to consider it.

I'm not familiar with the clips, but I'll see if I can find a UK supplier to see about cost.

Thanks again.

Why would you have to loose 6" - you can step the new joists up betwwen the old ceiling joist with no problem.

I can usually get a new ceiling down to only 1 1/2" to 2" of loss.

Rod

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Ignore the man behind the curtain........

Ahhh, I think I see what you mean. You run the new joists in between the old joists and use the new stud walls to support it?

Smart like the Dickens, that...

Would you recommend decoupling the new joists from the new stud walls somehow? Neoprene or somesuch?

No - the idea here is to decouple the new from the old - after that you gain nothing by carrying it further.

By the same token - you do not use RC if you have independant frames -

Rod

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Ignore the man behind the curtain........

Thanks for the input. I'm going to go out and have a look at the existing joists tonight and come up with a plan to build amongst them. Two questions, however, if I can bother you some more...

1. When putting insulation into the new ceiling, will it be necessary to cut it so it sits on either side of the old joists? Is the density of compressed acoustic/fire slabs going to be a problem for transmission if I just squish it in between the new ceiling and the old joists? I know that insulation usually counts as "airspace", but is that still the case when it's severely compressed; if it will compress that much?

2. Do you close off the ends of the new joists to keep the insulation from shifting around (though I don't know how that would happen) or does it even matter? If you do, how do you manage that with the old joists in the way?

I've searched and I can't find a diagram on the site of what we're talking about. But I seem to recall seeing one around here... Hmmm....

Anyone?

One additional question. How does one cap a double stud wall system when the two stud walls are a good distance apart - say 8"? Moreover, how do you cap and keep the airspace "airtight" when building a stud wall inside a brick or mortar wall? If the object is to decouple the new from the old?

Do a search here for firestop details

that should answer your questions -

I know they have been posted.

Rod

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Ignore the man behind the curtain........

Thanks, I wouldn't have thought of that. I know I've seen that kind of thing as well.

Here's a great detail for that condition.

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Ignore the man behind the curtain........

What a great idea. I never would have thought of that. So the old & new joist would be like interlocking your fingers.

I guess you would need to have nothing in between those existing joists: duct, gas lines, wiring, etc.

Very cool...

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- Brad

www.theSecretSystemBand.com

"...over the years, 'the-blues' has raised many children..."

Just did my first test on my build. All the walls are 2 layers 5/8 sheetrock with greenglue on reselient channel with ultratoch, then concrete walls. The ceiling is the same except I used 2 layers of 1/2" sheetrock. The final seal was the double doors at the entrance. My studio is not up and running yet so I took the stereo out of the bedroom, about 70 watts with a 10" sub. I put it on the wood floor with no mat, turned it up about 3/4 with AC/DC. Total silence.

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IS IT LOUD ENOUGH YET?