John Sayers' Recording Studio Design Forum Archive

Hello again,

I'm getting close to starting my construction on my basement studio. Nearly all of my information and planning has come from this forum, which has been totally indespensable. I couldn't overstate that.
I was a little unsure about room size etc... so I called someone here who works at an architecture firm as an acoustical consultant. She came out and took a look, did some drawings, answered some questions. Here is where I run into some new questions. She had some different ideas than what I understand to be true from this forum. so I wanted to run it by you.

First: my plan was to put two layers of sheetrock up inbetween the joists of my ceiling, caulk them, then hang another two on rc (actually http://www.pac-intl.com/products.htm one of these products)

She told me that the benefit I'd get from putting sheet up inbetween the joists would be negligible, and I shouldn't bother. I AM most interested in insulating the room from the house upstairs, but for the cost/value angle, if I'm not going to get much from it, then I'd rather not have to buy twice as much sheetrock for the ceiling, not to mention the time involved.

Second: As far as caulk goes, she told me that I could use ANY NON HARDENING CAULK. "They just charge more for the stuff that says acoustical" I'm pretty skeptical of this claim, since I've read here about how long it takes for something to harden/shrink. What is the Gospel on this?

Third: I'd been planning on doing a double wall construction, one of which would be lightweight steel studs. Since Steel has gotten SO expensive, she suggested I'd get the same benefit of using that RC type clip I linked to above, on a wood stud. Seems ok, and more cost effective. Agree?

Finally, I am considering using some glass bricks, to bring some light into the studio. I've read the couple of threads here that mention those, but definitely nothing definitive. has there been any response from anyone who's used them on how they are? They make Solid Glass Blocks, as well? those would be better? instead of hte hollow ones I assume?

Ok, I think those are the big ones. Basically, I've got hte plan, but she raised some questions in some important details. I think the most important question is the sheetrock up inbetween the joists... since that is a lot of cost and time.
thanks a million times over for all of the help.
David

David,

Third: I'd been planning on doing a double wall construction, one of which would be lightweight steel studs. Since Steel has gotten SO expensive, she suggested I'd get the same benefit of using that RC type clip I linked to above, on a wood stud. Seems ok, and more cost effective. Agree?

Granted steel has gone up, but is about the same price (when I checked last week) as what wood is. The last price I paid for 3 5/8" x 8' steel studs (25 guage) I paid about $2.88 a piece for. The 2x4's I looked at a couple days ago at H.D. was about $2.83 a piece.

Those RSIC clips run about $5.00 a piece average. Depends on quantity you buy from the supplier.

As far acoustical sealant, I leave that for someone else to answer, but the last batch I purchased (a case) I got the case price and paid $3.25 a tube for it.

Aaron

First: my plan was to put two layers of sheetrock up inbetween the joists of my ceiling, caulk them, then hang another two on rc (actually http://www.pac-intl.com/products.htm one of these products)

This is actually worse than having two leaves (floor, sheetrock). Can your ceiling support that weight?

The RSIC clips are fine, just put them right on the joists, then the sheetrock. Of course put insulation in between the joists also.

I can not answer the other questions effectively.

Have fun!
Andre

OK, in order -

1 - Ideally, you would rip up your upstairs floor and add two more layers of mass which are continuous over the top of your existing floor sheathing - this would be your upper leaf of mass for a mass-air-mass barrier. Then, after filling the joist cavities with fiberglass insulation, you would hang your lower leaf of mass (2-3 layers of sheet rock, and DIFFERENT from the upper leaf) on resilient mounts of some type, whether RSIC clips/channel or Resilient Channel - this is obviously a better way to go if possible.

Since very few people are willing to tear up existing construction, the next best thing is to increase the mass of the upper leaf any way you can; that's where the added layers of sheet rock between joists come in. I agree that it's not ideal, and that some flanking will occur through the joists, but the resilient mounting of lower layers will counteract that somewhat. I have no way of calculating the advantage these extra layers give, since they are NOT a continuous panel and ARE broken up by the joists - however, I've recommended this to dozens of members for both wall and ceilng add-ons and never had anyone come back and tell me it doesn't work. Without having done this myself (yet), theory and lack of negative feedback are all I have at the moment.

In most of these cases, every dB of isolation you can get is worth quite a bit - personally, I'd do it while the opportunity is there rather than NOT do it and find less isolation than I'd hoped.

2 - As for "charging more for stuff that says acoustical", have you priced caulk at Home Depot lately? First, all they carry are the small, 10 oz tubes - a decent, non-hardening caulk runs almost as much in 10 oz tubes as Aaron paid for 29 oz tubes that the "real" acoustic stuff comes in. This puts the cost per 10 oz tube at around $1.20 per - It's your nickel, but why pay MORE for stuff that "might" work?

3 - Steel isn't the only thing headed for the stratosphere these days - priced plywood lately? Performance-wise, either will give similar results - steel has the added advantage of fire resistance, which would be minimal when using multi-layer gypsum - you also don't have to find straight studs with no knots, etc - It comes down mainly to cost and preference in the long run - when building a single stud wall with steel, as long as it's a NON load-bearing wall you can use the 25 gauge studs and eliminate the need for RSIC clips/channel or RC - as soon as you change to double frames the equation becomes more balanced, since the double frame negates the need of resilient mounts in EITHER construction.

4 - Glass blocks - solid will be better than hollow, if you use two separate courses. That would give a mass-air-mass wall, for best isolation. The hollow ones have webs that continue through the block, so only part of the block is mass-air-mass - then, when you add a second course, you end up with a partial 4-leaf wall. You can't win... I've not seen specs on solid glass, all I know is that glass is approximately 3 times the density of gypsum wallboard. As such, 2" solid glass would have a critical frequency of around 250 hZ, with an attendant TL dip at that frequency - going to 4" thickness lowers this to half, which is still in the audio range. Using two courses of (preferably) different thickness with an air gap would improve on this quite a bit - rough calculations of 2" glass, 4" air, 4" glass show STC 55, with worst performance at 70-200 hZ (TL ranges of around 37-38 dB at those freq's) - Keep in mind, however, that these calc's are for SOLID glass, not individual blocks - the joining process will likely worsen the field results.

The only member that's done the glass brick thing is Jules, sounds like you found that thread - Jules is more of a producer/engineer than a chaser of details, so it's likely that the best you'll get is "it works fine" - this isn't very quantitative, although if it "works fine" I guess that's the main thing - I'd want more assurance than that for the labor involved (not dissing you, Jules, that's just me not wanting to work hard for less than I'd hoped )

Maybe you should print this out and discuss it with your local consultant, or have her chime in - that way, you'd get best of both and we ALL might learn something... Steve