Which is the better solution?

[Rod Gervais]

Originally Posted by RoughWood Studio

I have Rod's book now and think I understand more about 2 leaf walls.
Here is my situation. 2x4 walls with fluffy insulation inside. Both sides are half-inch chipboard under half-inch sheetrock.

The CR also has Auralex limp mass vinyl, then RC with two additional layers of half inch sheetrock. (...with huge amounts of big stretch at every seam.)

The limp mass helps a l ittle - but not a lot in comparison to what more drywall would have offered.

However the RC created a small air pocket between the inside face of wall and the new face of wall - and this actually hurt you rather than helped.

Electric boxes are not inset. They are surface mounted to the chipboard and trimmed out. This was always fine isolation for bands playing in the main room as the drummer is usually in his own good sized iso-room on the opposite side.

This helps........

But, when a drummer wants to track in the main room the bleed is just too much.

understandable

Should I remove the sheetrock/chipboard in the performance space and build another wall a few inches out, or could I just brick the wall (performance space side) and be done?

We have a friend in the brick business and he's got funky ol' 70's brick he'd almost pay me to take. And I have a brick-laying singer/songwriter who would trade labor for studio time. But if it won’t work…
Neither alternative is inexpensive. It's about 50 feet of wall 10 feet high.
What do you folks think?

There is a lot to this I can't "see" - thus take this advice with a grain of salt.

Assuming the wall is the weak link - masonry mass will help quite a bit - but if only a single thickness (as opposed to a free standing brick wall) there will be a loss of potential isolation because the single layer will still have to be tied to the face of the existing wall for structural stability. The best gain would be a completely isolated brick wall.

Now - if that wall is not the weak link - if the weak link is the ceiling - or the 2 walls that flank the party wall between the 2 rooms - or the floor - or the combination of all of those surfaces - then it is very possible that you might see little to no real increase in isolation gained with that work.

The level of isolation between spaces is only as good as the weakest link(s)

This is why testing labs have limits on the level of isolation then can certify isolation assemblies to - once they reach the limits of their isolating assemblies - they could put an assembly capable of completely shutting out the sound of a bomb on the other side of the wall and they would not measure an increase in isolation above that which their assembly is capable of.

Rod

[RoughWood Studio]

Please excuse me. I still don't understand. Would the mass of the brick attached to the existing wall not be as good as stripping off the chipboard/sheetrock and building another wall offset from it?
By the way... thanks for being a part of this forum.

[Rod Gervais]

There is no simple answer to that question, especially without knowing a lot more about the construction than I do.

I have no way of quantifying the level of additional isolation you're looking for - nor of knowing the weak links in your assemblies.....

The question you pose is not capable of being answered at a distance if you want any assurance of success.

Might it work - possibly - might it not work - possibly.......... we simply do not have enough pertinent data to offer a rock solid yes or no answer.

That the real answer......

As to your other question - assuming isolated construction in it's entirety - you can't get better than that.

With semi-isolated structure though - for example - the walls flanking this wall (left/right) and the ceiling are connecting the 2 spaces - however walls directly separating them would be isolated from one another (instead of connected with just a ton of mass) - then we are back to "perhaps"

Perhaps adding mass alone will get the job done - perhaps a 2nd wall isolated from the original will get the job done - and (worst case scenario) perhaps neither will get the job done.

Without being able to physically test the space I have no way of being able to predict the outcome in either case. Nor does anyone else.

Rod

[RoughWood Studio]

I understand. We could add mass and still have flanking sound, etc. I'm thinking the second wall is the way to go. Dang! I hate the idea of stripping off that chipboard/sheetrock. But now I understand why it's important.
Rod, thanks for your book and explinations on this. Best regards.

[Rod Gervais]

Happy to help

Rod