Does 2 leaf wall in garage create 3 leaf system?

I guess this depends on how far away from the garage walls the new room's walls are?

I've been wondering myself too 'bout that. WHEN are we talking about multi layer (more than 2)... (as in, how much distance). When building a room in a room using 2 leafs....

I've been wondering about the spaces in my rehearsal rooms and the fact that some rehearsal rooms with double leaf walls will be facing each other across a corridor. Do you need to worry about this effect when you're talking distances of 6 ft? Even if it is a problem, there wouldn't be much I could do about it short of rearranging the rooms, presumably, but I'd still like to know if it's a factor. I feel like people might aware of the effect but don't really know at what stage it ceases to matter, once the gap between leaves gets significant. At least I don't.

Good. I'm not alone. I'll try to simplify the question: At what distance from the garage walls can I construct a room and safely NOT create a 3 or 4 leaf partition? Here are the possibilities. Please tell me if they are correct: -Finished garage (2-leaf) + 'room within a room' (drywall both sides of 2 x 4 stud frame: 2 leaf) = 4 leaf partition NOT GOOD -Unfinished garage(1 leaf) + 'room within a room' (drywall both sides of 2 x 4 stud frame : 2 leaf) = 3 leaf partition STILL NOT GOOD -Unfinished garage (1 leaf) + 'room within a room' (drywall one side of 2 x 4 framing only - 1 leaf) = 2 leaf partition GOOD I understand all this to be true in theory. But let's say I come in from the garage walls by 1 foot. Will this still create the 3 or 4 leaf effect? Or is it safe? Thanks guys

thats ok to do. you want your first leaf as dense as possible your air gap as big as possible and your second leaf as dense as possible

greenlander wrote:

... Do you need to worry about this effect when you're talking distances of 6 ft?...

I think you've put your finger on a very seemingly likely answer... Although, no, I MYSELF, can't provide any evidence to support it, I truly believe that anytime a space between a leaf is real huge, any 'third-leaf' effect (although possibly still theoretically applicable) can become much less relevant, perhaps even irrelevant -- if the space is on the order of tens of feet, say... I know I've been a pia about this, but I've yet to see a side by side comparision of a PURELY three-leaf wall and a two-leaf wall (maybe it exists and I just haven't seen it).... What I have seen -- as most everyone else also has seen (and often tout) -- is that diagram where a layer or two of sheet rock on a two-leaf system is moved to the inside space, BUT is directly, physically attached to the inside of the studs... I can't understand how that can be considered a 'pure' three-leaf' system... It should have been done by somehow independently supporting a leaf in-between the two-leaves, without a direct, physical attachement to the SAME framing of the original two leaves!.... This would have been the correct comparison.... But, as it stands, it's more like comparing a 2-leaf with a 2.5-leaf, or something.... Does anyone else see what I mean about this? (I know it can be argued 'how do you 'suspend' a leaf between two other leaves?'.... but practicality is not the question I have... remember, this is all in a lab anyway...) After all, EVERY WALL can be considered more than two-leaf if certain, particular sets of two reference points are chosen, or if different system boundaries are chosen... try it out! (I think this was alluded to in another post above)... It's also possible that, IF there are large enough spaces between the leaves, an unavoidable three-leaf system could be superior to the alternative single-leaf system... If I'm wrong here, please provide specific details or data to correct me...

Luftweg wrote:

After all, EVERY WALL can be considered more than two-leaf if certain, particular sets of two reference points are chosen, or if different system boundaries are chosen... try it out!

I tend to agree. By a liberal definition - my outer walls are the third leaf between my neighbor's outer walls and my inner walls. Does that mean that in order to not hear my neighbors loud stereo inside their house I would be better off tearing off my outer walls? :lol: Something tells me no. s

See hugo_inside's "Avoid triple leaf... why??" thread from January 2005. 8) --Keith :mrgreen:

Thanks Sharward. I noticed you chose to beef up your outer walls to create a single leaf. Was this to conserve interior space? Or was this done to avoid the 3 or 4 leaf effect....

plus6vu wrote:

I tend to agree. By a liberal definition - my outer walls are the third leaf between my neighbor's outer walls and my inner walls. Does that mean that in order to not hear my neighbors loud stereo inside their house I would be better off tearing off my outer walls? :lol: Something tells me no. s

Refreshing to hear someone else gets that notion... With that, you can see that there must be limits to the 'power' of the third-leaf effect... Great distances would seem to negate it; and then OTHER factors would seem to become far more dominant, or much more troublesome and worthy of more consideration (in other words, don't cripple yourself with every thought concerned about whether something can be considered to have more than 2 leaves; but perhaps just not deliberately seek to utilize more than 2 leaves..)....

cjbdrm wrote:

I noticed you chose to beef up your outer walls to create a single leaf. Was this to conserve interior space? Or was this done to avoid the 3 or 4 leaf effect....

Indeed, it was to avoid the 3 leaf effect... But it was also to have a more massive outer leaf. --Keith :mrgreen:

For the sake of clarity, and for anyone following this thread, here's Rod's answer to a similar question:

rod gervais wrote:

Hugo, If you do it exactly the way you have detailed - with the air between the walls open to the space above......... then it isn't going to be a 3 leaf system. One of the things required for a leaf to be a leaf is the air acting as a spring - and thus the cavity must be sealed. Even if the outer room was a completely sealed cavity - the volume will be large enough to never effect the wall assemblies. Rod

In my case, I'm talking about an 'inner' room: my intent is to build a room smack dab in the middle of a 2-car garage, coming in from the garage walls about 6-12 inches. I have to assume now that the air won't be acting as a spring, as there is a large volume of air surrounding the room that can 'flex', if you will.

Wow, these are exactly the concepts I was trying to get at last year..... I was actually told (forget who) that the seal made no difference... and I couldn't see how it COULDN'T make a difference... Actually, it should be almost obvious that an extremely large volume, or distance between leaves, would not affect things much (that is to say, probably mitigates some other factors)... It's possibly even likely that, if only a small 'point' of a large volume had a close distance between leaves, that that large volume would also partially (largely?) negate the effect of the closeness... no?

rod gervais wrote:

One of the things required for a leaf to be a leaf is the air acting as a spring - and thus the cavity must be sealed. Even if the outer room was a completely sealed cavity - the volume will be large enough to never effect the wall assemblies. Rod

rod gervais wrote:

Hugo, If you do it exactly the way you have detailed - with the air between the walls open to the space above......... then it isn't going to be a 3 leaf system. One of the things required for a leaf to be a leaf is the air acting as a spring - and thus the cavity must be sealed. Even if the outer room was a completely sealed cavity - the volume will be large enough to never effect the wall assemblies. Rod

Now THAT makes perfect sense to me. Thank you for the clarification! With my situation, that gives me other options. :) Scott

If you check the BBC paper, you'll notice that the 3+ leaf effect diminishes greatly when there is increased air space between the leaves. The effect is really strong if you're building a 'thin' wall, but is greatly diminisheb by the time there is about 0.5 meters (1.5 feet) between the outer leaves. Check out http://downloads.bbc.co.uk/rd/pubs/reports/1995-06.pdf and compare the constructions in the middle of the document against those at the end. Cheers, Kris PS: Do note, however that the 2 leaf system still had better performance at all times.