to RC or not to RC

guitarguy · Post by **guitarguy** » Wed Aug 11, 2004 4:11 pm

Can anyone tell me if I am using one leaf walls
( one wall 2 x 5/8 drywall opposing leaf 2x 5/8 drywall + 1/2 dry wall sandwiched between)
on seperate concrete slabs, plenty of OSI sc-175 sealant, and Roxul Insulation.

Am I going to get any noticable, extra STC value out of the 2 x 5/8 drywall leaf using RC?

BTW... Happy to say framing has begun. Here's a pic of the control room so far...

giles117 · Post by **giles117** » Wed Aug 11, 2004 10:37 pm

Note the walls on the right of your diagram. That will qualify as a two leaf design. drywall on the inside of each room with rockwool bwtween the studs.

What you described is a two leaf (correct way to go) design.

so to reiterate

2-5/8' Drywall/Studwall - Airspace - Studwall/2-5/8" drywall w/ 1/2" sandwiched. On one of those opposing walls (between the CR and life room) place RC channel, but not on both sides of that 2 leaf wall.

Hope I didnt confuse you. Steve says this better than me.

guitarguy · Post by **guitarguy** » Thu Aug 12, 2004 2:11 am

Thanks for the reply Bryan. No you didn't confuse me at all. What you said is the plan.

I'm just trying to make sure that the money we spend is spent wisely.
Our primary goal is to build the studio the right way. Our second goal is to not spend more money than we need to.

RC is in the plan, but I'm just making sure it's worth the investment. The added rating you get from RC compared to the price is making me question it's value in Studio construction.

rod gervais · Post by **rod gervais** » Thu Aug 12, 2004 3:25 am

It appears to me that you are building 2 totally seperate walls - one framed on slab "A" - another on slab "B". There appears to be about 5" of air space between the 2 walls.

Inside the room I see in your picture will be (if i understand you correctly) 2 layers of 5/8" drywall.

Then insulation - then your 5"+/- air space - then insulation in the next wall - and then 2 layers of 5/8" drywall with a single layer of 1/2 sandwiched betwee those sheets.

If all this is correct - then NO you do not want to waste money on RC channel - you really don't get an advantage with it on double wall construction. The only real gain with RC is on single wall construction.

Now - understand that this deals with the walls I can see to the left and right of the picture........

The wall closest to me in the picture is a single framed wall........ and this (unless you are going to add another wall in front of it) would work better with the Resilient Channel.

Single stud walls gain if you use RC........ but if you add another wall this side of it - then don't bother..........

Rod

giles117 · Post by **giles117** » Thu Aug 12, 2004 5:58 am

Thanks Rod you finished it up I just got back ads was gonna tell him the improvement is minimal. Of course steve has a view of this to consider as well. but I think the improvement was like 2 or 3db total. I really dont recall. I think it was like you get additional LF damping. STEVE???

But considering RC cost me 1.43 each and I only needed 10 channels I didnt see it as a waste to get a db or so add'l TL

knightfly · Post by **knightfly** » Thu Aug 12, 2004 6:20 am

First, let me say that Rod has probably built more walls than I've driven nails (at least up to when I got my first nail gun

) so I wouldn't hesitate to take his word on any aspect of construction -

As to the RC on double frames - I don't remember the details at the moment, but I think I was "brain farting" in public at the time - the idea was that the RC would let one side of the wall flex more, which should theoretically give slightly better isolation at lower frequencies - however, the more I looked into this the more complex it became - I finally came to the conclusion that even as "anal" as I get, this was too far out for practical construction. Mainly, the computations for resonance, damping, change in mass-air-mass, etc, got so unwieldy that I pretty much gave up on it and decided that Rod's "KISS" method made more sense from a practical viewpoint.

If building a double framed wall and RC is used for some reason, I would be sure to completely fill the cavities snugly in order to dampen any unwanted panel resonance. Better; just forget it. By the time you get to double layer sheet rock on separate frames, flanking will destroy any slight gains you might see... Steve

giles117 · Post by **giles117** » Thu Aug 12, 2004 10:12 pm

Thanks for that clarification Steve. I thought i remembered that thread but I guess I missed the conclusion. LOL

Well there you have it. RC is optional. Although ... Steve's Rants had me using it. LOL (Just teasing Steve)

guitarguy · Post by **guitarguy** » Fri Aug 13, 2004 4:48 am

Thanks for all the reply's.

Bryan just in case I would need any RC anywhere could you tell me where you found it for that inexpensive of a price?

Post by **Aaronw** » Fri Aug 13, 2004 5:02 am

All steel prices have been going up an average of 15% a month. I had to buy some last week and it was $2.85 for a 12 foot stick. 9 months ago I paid about a buck and a half.

Aaron

giles117 · Post by **giles117** » Fri Aug 13, 2004 11:22 pm

Thanks aaron cuz i bought mine last year. All this stuff has gone up. Dogone gas prices.

giles117 · Post by **giles117** » Fri Aug 13, 2004 11:24 pm

Matter of fact i just made a call to the place I bought mine at 1.42 and they are now selling it at 4.15 a 12' section. Hmm guess these extra Channels i have... I need to find a buyer and make a profit. LOL

guitarguy · Post by **guitarguy** » Sat Aug 14, 2004 4:56 am

WOW, I may have to follow RC prices a lil closer. Seems it may be as good of an investment as Cisco stock was back in 1990.

Post by **Aaronw** » Sat Aug 14, 2004 5:42 am

The apparent "reason" is due to the fact China has been buying up all the steel...hence causing a "shortage" of steel. 'Tis the rumuor I hear anyway.

I think they're just jackin' up the prices to make a huge profit.

I'll refrain from a select choice of words...

giles117 · Post by **giles117** » Sat Aug 14, 2004 9:00 am

That's how I feel, just jacking up prices for the heck of it to pad those coffers.