Date: Thu Jan 18, 2001 5:39 pm
Subject: Re: [acoustics] orrect rc channel installation?
In a message dated 1/17/01 11:48:40 PM Pacific Standard Time, dude@c...
> So can someone describe the right way to install rc channel? If layed on
> it screws into the studs, then the sheathing screws into the rc channel,
> Leave the drywall floating and caulk the seams. Ok. Now if you sheath
> directly to
> the studs, then lay rd, what do you screw the rc to and what do you screw
> final sheathing layer to? Sounds like 2 layers of drywall or osb then
> drywall is
> much easier and yields same stc, perhaps better on low end...
Try this URL:
If the above comes out garbled, go to www.national-gypsum.com
and look for
product literature, then click on the option to have the manual displayed by
Section. There is a Section on RC that covers most of your questions.
Generally (from what I gather from various listed STC ratings) adding RC and
an additional layers of 5/8ths drywall to a wall is roughly equivilent to
going from a single row of studs to staggered 2x4 studs inside 2x6 top and
bottom plates. Both of these techniques reduce the coupling between the two
sides of the wall. Both serve to increase the STC and better than just
adding a layer of drywall, or adding R-11 to the cavity.
Obviously RC is the way to go if you are trying to beef up an existing wall
(since re-studding the wall would require demolition). In a new wall
consider doing both as the extra studs add little in cost and add a real
boost to the decoupling of the two sides (the top and bottom plates are the
only common connection between the two sides.
As to RC being the same as just adding an additional layer of drywall, I
don't think this is true. Say you have a unfinished common wall between your
house and your garage .... 1/2" drywall on the inside the house side, with
R-11 between studs, and no sheathing on the garage side. Given the choice
... say between three layers of 5/8's on the garage side vs. two layers of
5/8's with RC in the middle, I'd opt for the later. RC is a lot a lot easier
to put up than a third layer of drywall ... its just a matter of metal strips
horizotally attached 6" from the floor and ceiling ... and no more then 24"
apart in between. There is no finishing (mud-tape-caulk work), and the
finished STC is probably higher (I can't find a direct comparison of three
layers vs, two layers with RC, but the wall ratings that include RC jump up
there pretty high.
Also consider that using RC as a decoupling layer also serve increase the
differentiation of resonances between the layers, which would flatten out the
STC curve (I would guess that a free floated panel on horizontal RC will have
very different phase and resonances than the panel firmly mounted to vertical
studs ... with different spacings ... even when the same material is used.
Bottom line ... RC is a proven performer ... its easy to install too.
Scott R. Foster