Should I float these walls?

[aschatzb]

Hello:)

I'm about to start construction on the second phase of my studio,
secondary walls in the live room. It's about a year earlier then I had planned, but drums are bothering the neighbor...

The live room is built on a slab (about 20x20) The shell is typical 2x6 timbre construction, stuffed with fiberglass insulation and no finishes on walls. The ceiling is 20 ft. with vault, peaking about 24 ft.

The plan is to build all secondary walls, fillings in between studs with mineral wool and finishing w/2 layers of 5/8's gyps on all walls. The walls will be treated with acoustic panels (wood frames covered with fabric and filled with mineral wool). I will also be building a secondary ceiling joist system that sits on the secondary walls. 2 layers of 5/8s on ceiling. There will be no connections at any points between the structural shell of the building and the seocndary walls. room within a room.

The studio is built into a hillside, partially underground (9ft). The wall which is partially undergound is 12" concrete block (filled with concrete). The neighbor who lives up the hill from this wall (15 ft.) has complained to me from drum noise (kick drum).

Here's my questions: I don't plan on floating the floors in the live room. However, I'm considering floating the bottom plate of this secondary wall and perhaps all the walls in the room. Does anyone have any experience with this? Is it worth the trouble? What material should I float on (epdm sheet)? If I do it, are the special consideration while installing?

thanks:)

andrew

[AVare]

Please read this thread:

http://www.johnlsayers.com/phpBB2/viewt ... 31&start=0

Noting things like:

HOW LOUD are you, and how picky/loud are your neighbors? How close? This is subjective, so you will need to buy something like the Radio Shack Sound Level Meter

Andre

[aschatzb]

Hey Andre,

I'll get my hands on a sound meter. I imagine this will clue me into if I'll be able to realistically achieve the isolation needed to keep my neighbor happy.

In the meantime, I'm still wondering if EPDM under the bottom plate will do anything worthwhile?

thanks:)

andrew

[AVare]

Congratulations on the meter. The EPDM may help or not, or not even be needed. Your measuremtns will hlp determine the need.

Andre

[knightfly]

NO mention of your roof or ceiling; what is the construction of those exactly? Can you post some sort of sketch showing an elevation view of your place and your neighbor's place?

Hint: follow the weakest link.

Also, your description of intended wall construction is a bit vague - a sketch of that would also help, or at least a layer by layer description of the wall from outside to inside, including dimensions-

The more detail the better, since I'm not physically there to "snoop around"... Steve

[aschatzb]

Hello Steve,

I've created the most basic elevation sketch. We are about 15 ft from the neighbor.

The roof is engineered cathedral truss. Sheeted with 3/4 ply and shingled. The truss is lined with fiberglass insulation r-38. It looks like the truss is on a 2 ft. span. There is currently no ceiling in the space. It is unfinished.

The intended secondary wall construction is very basic. The wall is 21 ft long and 20-24 ft high depending on the cathedral. The wall will be framed with 2x6 timbre construction sitting 1" from the existing structural wall on the concrete slab. The wall cavities will be filled with the mineral wool. I've used 3 inch mineral wool in the past, but will try and get my hands on something thicker. Two layers of 5/8's gyps will be applied to the front side of the wall (inside the room), nothing on the back. Only the second layer will be mud and taped. I will seal between staggered joints with acoustic sealant, and leave a 1/4 gap at the bottom of the second layer at the floor to be filled with acoustic sealant.

The secondary ceiling (the first ceiling being the unfinished cathedral), will sit on the top plate of this wall. 2x8 or 2x10 joist depending on what I can get away with. The joist will be set at 16". Treated the same as the walls.

Let me know if you need some more details. I'm sure you will. I always try and think of everything, but never do!

thank you, andrew

[knightfly]

I always try and think of everything

Actually posting the sketch would maybe help...

[aschatzb]

Sorry, You caught me while I was removing a image that was way too big... I didn't want to get in trouble;)

[knightfly]

NO prob, just flickin' ya, and thanks for staying small (although a bit bigger would be OK, just so it's under 750 wide)

Your basic idea seems fine; right now your single leaf of mass (the roof) is why your neighbor is complaining, your plan will solve that if done carefully. One change - I would mud/tape/sand ALL layers, being careful to fill any cracks in the process. You want an UNBROKEN mass for ALL layers.

When figuring out what to do with containment, it's easiest to first visualize an OUTER mass shell that's unbroken - make that as heavy as you can, then do it again for the INNER mass shell. Enough insulation (NOT foam of any kind) to damp the panels, making sure it can't sag and leave un-insulated areas between leaves, thorough caulk and seal techniques (including putty packs for any and all electrical boxes) and you should be good to go.

If your outer wall's inner surface is still open (the part that isn't concrete) it won't hurt to add a couple layers of gypsum between studs for more mass - you weren't clear as to whether that wall has both inner and outer paneling installed, but there should NOT be paneling of ANY kind on the inside of those studs - you want mass-air-mass EVERYWHERE between you and the neighbor. No 3-leaf walls, or your drums will STILL bother them... Steve

[Xalky]

One change - I would mud/tape/sand ALL layers, being careful to fill any cracks in the process. You want an UNBROKEN mass for ALL layers.

Steve: thanks for bringing this up. I was under the mistaken impression that the under layer of the dbl layer didn't have to be taped but only caulked at the seams. So it has to be taped, OK.

This brings up another question. How about the wall and ceiling corners, Do they get caulked or taped? If so do both layers get taped or just the finished layer. Here again I thought it'd be better if the corners were caulked rather than taped, Am I wrong? I thought not taping the corners might offer better damping.

Marcel

[knightfly]

Best corner strength for multi-layer is using a "zig-zag" joint, where you put up ceiling layer, then east-west wall layer, then north-south wall layer, then second ceiling layer, then second east-west layer, then second north-south layer - this gives the strongest corner, and caulking should happen at each step.

If you use corner tape at all, the newer flexible plastic should give slightly better damping - as you surmised, caulking at corners will (reportedly) lessen coupling between walls and ceiling, and between adjacent walls, so it's a good idea.

The zig-zag joints are mechanically stronger in the event of catastrophic failure of fasteners (ceiling won't be as likely to fall) but arguably slightly WORSE for isolation, as compared to floating both ceiling layers INSIDE the walls and caulking as you go - but this would be mainly for resiliently mounted ceilings on joists that are common to above floor - I doubt it would matter much which method is used when fully separate frames are used.

As far as taping "in the field" (between sheets on a wall) as opposed to corners, the tape would mainly make sure no mud squishes back out (tecnical term :=) - if there were a way to make everything stay put without paper, it might be OK.

Main thing is, you do NOT want the tapered edge on the long side of most wallboard to cause a VOID in your wall mass, so it needs to be brought out flush with mud and tape for THAT reason, if no other.

HTH... Steve

[Xalky]

I question wether not zig zagging the corners would be better in a resilient mounted ceiling (as my setup will be). The zig zag pattern seems like it would offer some sound reduction in the corners as opposed to a straight caulk line. But I could be wrong there.

I planned on caulking all the corners rather than use mud, Thanks for confirming that for me.

As for the mudding the bottom layer. If the first sheet were mounted inside out so that the taper is inside the cavity, would this negate the need for mudding the joints? Could I just caulk them if that were the case? or Might there be some other reason such as a solid mass being better, The mud would solidify the first layer as one mass. I do understand about the void created by the taper could create a resonance.

Let me know if I'm on the right track?

Marcel

[knightfly]

You can actually buy NON-tapered sheet rock if you find the right source, but turning the normal stuff around would only help a LITTLE; there would still be less thickness/mass at the joints, only now if you were to suck the boards up against the framing it would tend to bow the panels outward about 6-8" from their edge, causing other potential problems.

What you want is the full thickness of each board EVERYWHERE in the field of the wall, through all corners, no exceptions. This can be done either by mud and tape of all layers, or buying the non-tapered stuff (I've not seen it in Home Depot type stores) - remember, the name of the game is MASS (Mass Kicks Ass :=)

As far as the joints go, I tend to favor the zig zag method as does Rod (which is even more telling, IMO) - the combination of a longer, more tortuous path for sound to weasel it's way through, plus several beads of caulk instead of two... Steve

[aschatzb]

Hey Guys, Steve thanks for taking the time to walk me through the process. It's always a terrible feeling when you read instructions and you realize you totally skipped a step the first time you hung a room. Though, that's beside the point (Even though the control room turned out great without the first layer of mud and tape, though I caulked the hell out of the first layer).

Anyway, back to using EPDM or something else under the bottom plate, should I?

thanks:)

andrew

[knightfly]

I wouldn't bother with that, you can get into worse resonance problems with than without; on concrete though, I would use Pressure Treated bottom plates for framing AND a thermal break; either a foam "sill seal" product as is used on perimeter foundations under the sill boards, or strips of 30# building felt (heavy roofing felt), 2 layers of this will work. You're doing this to keep the bottom plate of your wall from wicking moisture up from the slab.

I'm actually more concerned that your roof may be a problem; what's the plan for the vaulted section shown in the upper right corner, as far as maintaining the mass envelope of the outer shell?

I say this because it's doubtful your 12" filled concrete blocks are your weak link, yet your neighbor isn't happy... Steve