Outside Walls agains Concrete walls

JOHNNYGATE · Post by **JOHNNYGATE** » Fri Oct 29, 2004 9:30 pm

What do I do with outside walls that are against the Concrete Block walls, and the Garage Door? Do I build a wall on the floor with 2 layers of sheetrock then stand the wall up? Is this the technique used?

cadesignr · Post by **cadesignr** » Sat Oct 30, 2004 3:43 am

Hello Johnnygate, let me ask you a question. Are you building INSIDE OUT walls here? If so, yes, that is how you would have to do it. Otherwise, how would you attatch the sheetrock? If not, then you would build the frames on the floor and raise them, THEN sheetrock. However, I have ANOTHER question. IF these are INSIDE OUT walls, how deep of an airgap are you leaving between the sheetrock and the concrete block? This airgap SHOULD have a layer of insulation within, and if you already planned on insulation, how are you keeping it in place before the wall is raised? Also, your heading states "against concrete block". You are NOT putting the sheetrock directly against the exterior wall are you?

fitZ

JOHNNYGATE · Post by **JOHNNYGATE** » Sat Oct 30, 2004 10:50 pm

Are you building INSIDE OUT walls here?

Yes, (I think thats what your refering to) I will build a sub floor and will build the walls on the ground with two layers of sheetrock, steel stud, raise walls on top of each subfloor, a layer of insulation(what kind? BTW), RC, two more layers of sheetrock . But Knightfly says only one air gap so should I even bother building inside out walls?

You are NOT putting the sheetrock directly against the exterior wall are you?

NO!

JOHNNYGATE · Post by **JOHNNYGATE** » Sat Oct 30, 2004 10:54 pm

Also, how do I approach the ceilings? I do not want to use my existing ceiling. I have an 8'3" room so will still end up with about an 8 foot room with a sub floor and sub ceiling. The room is in the garage which has sheetrock and insulation timber trusses on concrete block. That is the construction of the existing room. What do you guys recommend?

knightfly · Post by **knightfly** » Sun Oct 31, 2004 6:17 am

Johnny, if your concrete block walls are hollow blocks you may already have both masses in your mass-air-mass ideal; you may have little choice but to end up with a 3-leaf wall if this is the case.

If that's true, then your best bet would be to use at least three layers of wallboard on the inside of the new frame, using resilient sway braces to stand off the tops of the new wall frames from the concrete blocks;

As to the ceiling, how new is this place? Specifically, do you have access to the builder, and can you find out what load ratings your trusses are designed for?

I'm asking this, because in order to maintain a complete mass-air-mass envelope around your space, you would need to add a second layer of wallboard to the existing one on your ceiling joists (which are the bottom chords of your trusses), then find a way to RESILIENTLY suspend a frame from that assembly and, leaving at least 4" or more air/insulation gap, add two more layers of wallboard. The outer layers should be caulked to the block walls, and the inner layers(and the new suspended frame) should hang INSIDE your inner walls and be caulked to (but not in hard contact with) the inner walls.

Another problem, especially in your area, is moisture; your building code may actually require you to put moisture barriers in place that can cause premature failure of your construction - read this summary for an idea of this -

http://resourcecenter.ashrae.org/store/ ... nid=893497

I know this all can be confusing; a lot of the problem is that the phsyics of sound isolation don't always coincide (if ever) with the codes that are intended to promote SAFE habitat; so far, I've not found a cut-and-dried solution for BOTH, only work-arounds that minimise the damage to sound isolation while (usually) satisfying codes... Steve

JOHNNYGATE · Post by **JOHNNYGATE** » Sun Oct 31, 2004 12:06 pm

why cant I just build "mass air mass" rooms inside of the garage?

JOHNNYGATE · Post by **JOHNNYGATE** » Sun Oct 31, 2004 12:09 pm

"If that's true, then your best bet would be to use at least three layers of wallboard on the inside of the new frame, using resilient sway braces to stand off the tops of the new wall frames from the concrete blocks; "

this seems easy..

"resilient sway braces " ??????? what are these?

knightfly · Post by **knightfly** » Mon Nov 01, 2004 1:14 am

"why cant I just build "mass air mass" rooms inside of the garage?" -

Because I said so

(Just kidding; actually, it's because the existing garage walls will act as a third or even fourth leaf in your "containment envelope", and that will weaken the isolation significantly at lower frequencies - these are the hardest to stop anyway, and weakening the walls at these low frequencies will un-balance the Transmission Loss of the wall, which in turn makes the wall sound even wimpier than it is (the human ear wants to hear all sounds at balanced levels; when it doesn't, it assumes that ALL the sound is as loud as the part that's getting through...

""resilient sway braces " ??????? what are these?" -

They are special braces you use at the tops of walls to keep them from tipping over, or just getting out of line; they have resilient inserts between two halves of the bracket to keep any hard contact from happening between the wall and its neighbor, usually a second wall frame. Here's a commercial example -

http://www.kineticsnoise.com/arch/noise/psb.html

http://www.kineticsnoise.com/arch/noise/kwsb.html

And one way to do it DIY if you're handy with tools -

http://www.johnlsayers.com/phpBB2/viewt ... 0176#10176

http://www.johnlsayers.com/phpBB2/viewt ... =7501#7501

Hope this helps... Steve

JOHNNYGATE · Post by **JOHNNYGATE** » Tue Nov 02, 2004 12:14 am

Its in a garage with a 2 car door. Wont the bass leak out enough with that door?

knightfly · Post by **knightfly** » Tue Nov 02, 2004 1:53 am

It will leak out MORE than enough, unless that's what you WANT - otherwise, you'd need to build a double leaf, heavy wall to seal off the garage door too. Were you intending to do that, or do you need the door to still function? Steve

JOHNNYGATE · Post by **JOHNNYGATE** » Tue Nov 02, 2004 3:45 am

Just to clarify for myself... My question is, when building a "Mass / air / Mass" studio inside the existing the garage, do the surroundings (concrete walls, ceiling) even matter because the low frequency pressure will just escape through the large garage door in the front? I don’t care if I hear a little outside the house.. I do not want the sound in the house though. That’s why I didn’t want to use the existing ceiling at all. I wanted to build 3 separate rooms, Control, drums, main room.

The volume is not what Im focusing on. Its the un-balanced Transmission Loss.

I am not going to use the garage door. I will remove the curved track and put some small straight track straight up to hold the top of the door.

AVare · Post by **AVare** » Tue Nov 02, 2004 5:25 am

do the surroundings (concrete walls, ceiling) even matter because the low frequency pressure will just escape through the large garage door in the front?

Low frequency is no teh only thing that will go throught he garage door opening. You have to isolate that also. Otherwise the sound will go through that opening and through the outside into the house.

Andre