John Sayers' Recording Studio Design Forum Archive

I am surpirsed I missed this in all of my reading on this great site. But, in case it is not mentioned, I will offer a tip or two by way of sharing my little bump in the road.

I am building a single room for practice and recording. 10 foot ceilings. Now when I installed my resilient channel, I thought I was following directions when I placed my bottom channel about 2-3 inches off of the floor and proceeded to install the remaining channels on 24" centers with the top not quite being 24" because we started 3" off the floor.

Now, when we went to place our first piece of 4'x8' drywall on the channel we discovered that to start with the drywall near the floor (~1/4" gap) would result in the drywall not reaching the resilient channel now located at ~8'3" leaving a 21" span of unsupported drywall. So, we had to lift the drywall up 3" to install. Now I have two gaps to fill, the top gap of just under 2' and the 3" gap at the bottom.

LESSON: Never use 8' drywall unless you have 8' or less tall walls and/or place your resilient channel at the 8' "installed" spot first and work off of that.

I am returning the drywall for layer 2 and getting 12' sheets.

Dennis

Dennis,

Let me put this in perspective for you if i can.

The layout of the RC should be from the finished floor - + 1/4 - 3/8" to center.

The one installed by the floor then lifts up - so a standard sheet installs perfectly.

You would have been better suited to move your RC than to install the drywall as you did - a piece 3" high at the bottom is going to be basically useless due to the fact that it will not be a rigid assembly matching the body of the rest of the wall. It will just flex at the attachment point.

You should not have any piece of drywall that does not connect to at least 2 RC members.

You might want to think about fixing this - you wall assembly is going to isolate only as good as your weakest point - and this detail that now exists at the bottom of the wall will cost you somewhere in the area of 20 to 30 db loss in seperation.

By the way - FWIW - in professional installations - the drywall is always run horizontally - not vertically.

Rod

Rod,
I have seen some “expert” advice that doesn’t quite match-up with your comments. Please take this as constructive not argumentative. I’ll summarize the two points of disagreement and leave the text quotes in tack:
1)They specifiy to install the lowest channel 2” above the floor.
2)The inventor of Gold Bond RC says to mount the wallboard perpendicular to the channel or you may compromise the system design.


Directly from the Auralex site which quotes directly from the “Gypsum Construction Handbook”.
The following three JPGs are taken directly from the Gypsum Construction Handbook published by USG. They illustrate the proper installation of RC-1 channel (a) on the stud/joist/framing, (b) as part of a wall system and (c) as part of a ceiling system.
(a) Rc1_1.jpg
(b) Rc1_2.jpg
(c) Rc1_3.jpg
Other recommendations made in the Gypsum Construction Handbook:
….
'• Locate channels 2" from floor and within 6" of ceiling.
…
Section 7.4 of the Noise Control Manual for Residential Buildings by David A. Harris. David invented the Gold Bond resilient furring channel (commonly known as "hat" channel) back in the 1960s. A PDF of Section 7.4 can be downloaded here.

“Wallboard should be installed perpendicular to the resilient channels unless approved otherwise by the manufacturer. Gypsum wallboard has a different stiffness across the width than lengthwise. The result will be a compromise to the sound or fire rating and/or a sagging ceiling.”

What do you think?

Thanks,
Dennis

p.s. I am planning on using 12 foot pieces for the second layer (cut to 10ft) which will cover my intended “patch” of the first layer’s 2” gap. Shouldn’t that second layer keep the first in place?

Dennis,

1)They specifiy to install the lowest channel 2” above the floor.

This is correct - but that is the only member that is supposed to be raised the 2". Everything above it should be installed normally.

In other words - if you are using 2' layout for your RC - the 1st piece is 2" AFF to the bottom ( and reversed) - the next piece is 24" to center of RC - then 4', 6', 8', and (finally) the piece installed 1" below the ceiling.

That way standard wall covering materials still install properly. The fact that you have a bay at the bottom that is 2" smaller than the rest is of no more consequence than the one you have at the top.

2)The inventor of Gold Bond RC says to mount the wallboard perpendicular to the channel or you may compromise the system design.

1st off - i re-read my post and apologize for not being clearer. The 1st sheet should be installed as you did - it's the 2nd layer i was concerned with.

I still however, maintain that the top sheet is to be installed parallel with the RC.

The USG manual (which i consider pretty much the "Bible" of drywall) - states that in single sheet construction the sheets should be installed at a right angle to the framing - i.e.: parallel with the channel.

In 2 layer applications - the base sheet is to be installed in a vertical manner - and then the top sheet is to be installed parallel with the channel.


Here's a link to the USG website Construction Manual - slip to page 119 and read what it has to say - it's pretty clear.

http://www.usg.com/Expert_Advice/Constr ... en)_03.pdf


The problem you have with that bottom piece (the 3" piece ) is that it is going to "hinge" at the point of that channel and not stay tight to the sheet above - I really don't believe it's going to give you what you want - tis gonna be a "weak point" in the wall assembly.

Picture that when installed - you will be able to push that piece in towards the wall with a finger - it will not be rigid - and the top sheet won't brace it in that direction - if it spans at least 2 strips of RC then it would be a rigid member - and that is the issue at hand.

Rod

The layout of the RC should be from the finished floor - + 1/4 - 3/8" to center.

From this thread I might conclude that the finished flooring gets put in FIRST and then the RC/wallboard goes up...OR? Seems like the walls should go up first with a gap at the bottom for caulk (?), then the final flooring put in and stopping just shy of the wall (and sealed with acoustical caulk...)-please clear this up for a novice.
dean