Drywall on the 'outside portions' of NEW structures? (as per Rick Fitz's STC chart)

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Ok Ok I see :) Let's still have a beer!

Rod - you stated:

"I meant the deck itself - tight to the plywood - this increases the upper leaf - but does not create a 3rd leaf (no air space between the plywood and drywall)."

I'm a little 'stunod' (slow), I understand :eek:

Ok Ok well perhaps it's not too late to fix something here:
http://home.ucwphilly.rr.com/livesound/3rd-leaf-1.jpg

And please read my last statement:
In general, I think I see the bigger picture here:
http://home.ucwphilly.rr.com/livesound/rick-combo.jpg
Do I take this illustration to mean:
JUST LEAVE ALL THE NEW OUTER SIDES OF ALL THE NEW WALLS OPEN WITH EXPOSED R11? As illustrated in these photos:
http://home.ucwphilly.rr.com/livesound/fitZ2-2-a.jpg
http://home.ucwphilly.rr.com/livesound/fitZ2-a.jpg

OR

Perhaps I can cover the 'OTHER' side of the wall that will have the exposed R11 with some nice colored flame-retardant fabric? (so as to keep the fibers from being airborn) Know what I mean? Would this be ok?

Best Regards
Michael Fraticelli
ROCKON@ucwphilly.rr.com
 
Last edited:
Holy smoley, EVERYONE popped in to visit while I was typing my reply :D What? Is everybody playing hooky from school today :p Hahahahaha!



In general, I think I see the bigger picture here:
Click to expand...
Correct. Imagine the WHOLE room as a 2 leaf system, EXACTLY like that. However, in
http://home.ucwphilly.rr.com/livesound/fitZ2-2-a.jpg
the adjacent room in the picture(tool/work area?) is what I thought to be the area where your airconditioner/vent fan was to be, correct? Now, from what I understand from Steve, the side of your iso wall in the first picture(facing into this area) COULD be EITHER.....#1insulated but not sheithed with drywall...depending on the issue of whether this room is an AIRGAP :D or..#2.....must be isolated further from noise GENERATED in this area :confused: :p(confusion compounded by more questions??????? :rolleyes: ) I would think that IF, you sheetrocked the OUTSIDE(inside adjacent room) this would NOW become a two leaf system itself, which with the other walls of this area being ALSO 2 leaf walls
creates another airgap(room) which in effect......makes this WHOLE SYSTEM a ......4 leaf system..ARRRRRRGGGGGGGGGG!!!!(ONE of those other walls has the IN WALL AIRCONDITIONER, RIGHT? Michael, I am not experienced enough to give an answer to THAT ONE......... :rolleyes: I'm simply trying to PROD the other guys into explaining a correct solution :D . Hahahaha!(Isn't this wall the one isolated from the beam above it? So no flanking can get through above this wall, is that correct? Man, I'm glad I'm not building this one.. :p with stairwells, shops, garage doors, existing floors above........you must be a glutton for punishment! :D :D
fitZ
 
Mike,

nope - you do not want to finish the oputside of those walls that way.......

When you have a room within a room - and this creates actually 2 rooms - then you want to install drywall on the outside that maintains your seperation.

Picture (if you would) a hotel corridor........

I have walls either side - with seperation assemblies of perhaps an STC 54 between them and the corridor.

I don't view this as a problem because I am only concerned with the seperation from the corridor.

It isn't the same as it is with 2 walls in close proximity to one another (talking inches here.).

SO what you want to do is finish the outside of the walls with 2 layers of gyp - and return this to the exterior wall - leaving a 1/4" to 3/8" gay and caulk the edges.

As far as that other wall goes - you would still be better off (IMHO) finishing the inside than not. That being if you can't undo the drywall you installed there to begin with (that would be the best).

The problem with this is that the material is installed diurectly to the outside wall and will transfer sound through the structure regardless of your interior finishes.

So if you're going to leave it in place - you will still get better - although not as good as if you took it off though - but still better isolation than without drywall on the inside face of your new wall.

Rod
 
Rod - Just FYI:

This is from Title 25
Chapter 25-12-3
Of the Land Development Code of the City of Austin
in reference to the Local Amendments to the Uniform Building Code.

(3) The interior wall surface of an exterior wall must be minimum ½ inch gypsum board or plaster installed on the inside of the wall studs.


Now, there are alternate compliances.
But those must be approved, on a case by case basis by the Director of Code Compliance.
 
Rod - you have a lot of patience :)

Rod you stated:

"As far as that other wall goes - you would still be better off (IMHO) finishing the inside than not. That being if you can't undo the drywall you installed there to begin with (that would be the best)."

So then I should leave this outer wall (which I just drywalled), alone?
Inner wall treatments to the same wall will have No effect?
http://home.ucwphilly.rr.com/livesound/layout-16.jpg

Rod - you also mentioned:
"Picture (if you would) a hotel corridor........
I have walls either side - with seperation assemblies of perhaps an STC 54 between them and the corridor. I don't view this as a problem because I am only concerned with the seperation from the corridor. It isn't the same as it is with 2 walls in close proximity to one another (talking inches here.)"

And that I should indeed try to drywall the outsides
of the sub walls - correct? Unfortunately I can't get to all of the walls as you can see here:http://home.ucwphilly.rr.com/livesound/layout-15a.jpg

Soooo then should I just drywall those outer sides that I can get to? That are accesible?

Best Regards
Michael Fraticelli
ROCKON@ucwphilly.rr.com
 
Michael, for your ceiling I would (if at all possible) continue to remove the middle leaf, or at the least drill as big and as many holes in it as possible; Rod (as usual) is right on this, and Rick's comment about the holes is good but doesn't go far enough. According to conversations I've had with Eric Desart (Galaxy Studios, over 100 STC isolation between EVERYTHING) even a panel bass trap up against the wall will weaken that wall at the combined resonance of the trap and wall. So, just venting that middle leaf (as in not sealing the air cavity) will NOT remove it from the equation. Only large and lots of holes can do that. (I'm talking hole saw, maybe 3", spaced so your perforation percentage is at least 30%, more if possible. Just plain removing that leaf would be best.

As to the insulation being left exposed on your outer walls, I would think that would depend on the volume/spacing of that hallway, and whether the door at the end of it is a good, solid, well-sealed one; is there a floor plan somewhere I've missed? I'd like to see the relationship of your room, where masses (all of them) are located, etc -

As to your comment about there being "not very big gap" or something to that effect, re the ceiling framing - even 1/8" air space between panels constitutes making those panels into separate leaves of mass - the air between them is still a spring, and still has (in conjunction with the mass of the individual panels) a mass-air-mass resonance, at which the panels will be nearly invisible to sound. This is why we strive for at least an octave or more below audibility for resonance in structure if at all possible; that puts the "pass thru" frequency so low that nothing we would ever generate or listen to (or care about) will be at the wall's weakest frequency.

When I use the term "wall", BTW, in this case (and in any case where theory is the main thrust) I really mean ANY sound barrier, whether wall, ceiling, floor, door, window, whatever.

The part of this I'm NOT still clear on, though, is the hallway scenario; if this hallway is effectively a sound lock, and if you will EVER have to open the door at the end of the hall while making noise (seen in http://home.ucwphilly.rr.com/livesound/fitZ2-2-a.jpg ) then I would consider the outside of your room frame as your outer containment, and live with the resulting 4-leaf scenario made up of the inner/outer leaf of the room wall, and the inner/outer leaf of the wall that door is part of. This is because otherwise, when you open that door there is (as near as I can tell) only ONE leaf of mass between you and the world (if that's what's on the other side of that door) - and this would let quite a few buckets full of sound escape to the neighbors.

If the above paragraph is an accurate assumption, then you would need to either do a double frame for that wall (best) or at least decouple one side or the other with RSIC's or RC.

If I'm making any wrong assumptions on what goes where, it's because I've not seen a floor plan; if it's already up, I could use a link in order to find out how far I've "swallowed my foot"

As to fireblocking in double framed walls, so far everything I've seen says that if it's full of insulation (especially rockwool, but even fiberglass) then it is fireblocked. So much the better for sound, since filling a wall completely also helps the TL.

Hope that helped, now if you could just point me to a floor plan... Steve
 
Mike,

you said:
It isn't the same as it is with 2 walls in close proximity to one another (talking inches here.)"

And that I should indeed try to drywall the outsides
of the sub walls - correct? Unfortunately I can't get to all of the walls as you can see here:http://home.ucwphilly.rr.com/livesound/layout-15a.jpg

Soooo then should I just drywall those outer sides that I can get to? That are accesible?
Click to expand...

No - it isn't the same at all with small sealed spaces and wide open hallways... and one of the reasons for this is the amount of pressure that the spring (the air spring) can build up in the space.

The fact is that you lose big TL values when you do this inside a wall with only inches in the equation - and you gain slightly when you do it with a hallway - and the bigger the hallway the more you gain until you reach a point where you gain the actual value of both walls (enough seperation to completely negate the multiple) and beyond that you gain for the additional distance of travel.

So it is anything but the same.

HOWEVER - in order for this all to work it is very important that you maintain the isolation from those small pockets within the wall and this "corridor" you are creating.

That is why I stated that you have to take the exterior skin of your wall and carry it all the way to within 1/4" to 3/8" of the exterior face of the outermost wall and then caulk. (I hope it goes without saying that this has also to continue to the roof/ceiling as well (whichever the case may be)).

This (then) maintains the room within a room effect.

Clear as mud????????????

Rod
 
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