wall construction questions.

Hey all, a couple of wall construction questions. In regards to using multiple layers of sheetrock/drywall with Green Glue in between, should the first layer also be mud and taped, or caulked is in the obvious case of the second layer? I know to keep the seems between the two layers away from each other but not sure if the first layer needs mud and tape as well. another question. When using the pink fluffy stuff for insulation, it usually has a paper flange to staple to the 2X4 wall studs. What do people do when using 2" rigid fiberglass or rockwool inbetween the 24" oc wall studs to keep them in place? since there is obviously some "play" with the fiberboard being only 2" and the wall stud being either a 2X4 or even 2X6. I keep reading threads saying though, that the fluffy stuff will do just as well as more expensive rigid fiber board or rock wool in a decoupled, two leaf wall system. And finally, hell, i'm gonna get murdered for asking this.. I've read all the stickies about the whole floating floor ordeal. But these all are usually in regard to building your room onto a concrete slab. Where can I find some info on whether to do this on floor contructed of wood planks on 2X8's above a crawl space and storage basement? I'm guessing, "Don't worry about it" will be the answer as well as "you don't have the budget". I have been interested in the "layers of 703 and mdf" techniques Rod and others have suggested though. Thanks for your time.

trodden, Most important first... Floating floor You should really go back a re-read that sticky... I think you're evidently taking away just the exact opposite info of what you should have, other than it's IS going to be EXTREMELY expensive to build a floating floor over a crawlspace/basement... to the tune of a structural engineer, ripping out the floor, putting in much larger joists (double to triple 2x12 joists) and even then, you'll likely need support posts under those massive joists, if you're talking true room within a room design for a construction project of any size. Now, about mud/tape on the first layer... Technically, you should mud/tape. However, I didn't. I caulked the 1st layer of gypsum with SilenSeal caulk. I think you would be OK with just caulk, as I was, but only if your seams are butted real tight. Then too, I also used 3/4" OSB as my first layer against the studs, and caulked that layer with OSI's SC-175 acoustic caulk. As far as the joints go, I would put the first layer of gypsum (wide side) vertical and your 2nd layer (wide side) horizontal. (It's actually cheaper to mud/tape as opposed to caulking.) Depending on your stud size and the air gap between the 2 walls, you should save you money for screws, caulk and other misc hardware, and just use pink fluffy in your stud bays. Max

I'm with Max. I might be tempted to suggest first layer go on horizontally, next layer vertical.

Hey Max and Ted. Thanks for the info. Yeah, i figured the floating floor idea should be thrown way the "f" out... I'm amazed that people want to do it even when they are on a concrete slab... but here I am, on this decking structure, where it is more resonant than a solid mass of concrete.. wasn't sure if the flanking issues in regards to the orignal flooring are going to be a "weak link" in my build. Therefore, i WAS considering the layer of 703, and couple of layers of MDF suggestion that keeps popping up here and there for drum risers. probably overkill, just kinda hoping i can isolate the booth enough where i can continue overdubs of marshall stacks turned up to "11" past the noise curfew hour. I live in an industrial/artist neighborhood so everyone is really tolerant of the needs to make a racket as long as you don't abuse it. This is in regards to an larger isolation booth i hope to be constructing in a couple of months after doing some more research. Won't be tracking full bands here.. Don't have the money to retrofit this whole place for that when there are plenty of already completed studios in town.. Just need a place for overdubs and mixes so I can be more flexible with working with smaller budgets. Cheers, Brandon

In regards to the "inside out" walls. It seems that rigid fiber board is preferred. How are people keeping the fiber board in place inside of the 2X4 frames? Since its 24" OC, does it just "fit" in there ok?

Less dense (thermal) insulation is better performance in the low frequencies.

Ted White wrote:

Less dense (thermal) insulation is better performance in the low frequencies.

as in "the pink" or "fluffy" stuff? How come I see soooooo many people using rockwool or 703 type stuff in their inside out walls?

Yes, the fluffy (thermal) pink, yellow or white stuff. Recycled cotton, cellulose, and recycled polyester also work well, as does mineral wool. See the NRC data in their IR 693 report http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir693.pdf Perhaps I'm mis-understanding. What I'm referring to are insulated sealed cavities in walls, floors and ceilings. Exposed insulation on the wall or ceiling surface is for in-room reverb control, and you see 703 commonly used.

Ted White wrote:

Yes, the fluffy (thermal) pink, yellow or white stuff. Recycled cotton, cellulose, and recycled polyester also work well, as does mineral wool. See the NRC data in their IR 693 report http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir693.pdf Perhaps I'm mis-understanding. What I'm referring to are insulated sealed cavities in walls, floors and ceilings. Exposed insulation on the wall or ceiling surface is for in-room reverb control, and you see 703 commonly used.

Thanks for the info. Yeah, "inside out wall" the plaster board is on the other side, while the insulation is merely covered by fabric.. therefore acting as sound treatment for the room as well. So mineral wool/rock wool works better than say a 703 type substance within sealed walls. Good to know, cause its usually cheaper.. but yeah... the fluffy stuff is cheaper than all!

Thanks for setting me straight on what an Inside Out wall is.

trodden wrote:

Ted White wrote:

Less dense (thermal) insulation is better performance in the low frequencies.

as in "the pink" or "fluffy" stuff? How come I see soooooo many people using rockwool or 703 type stuff in their inside out walls?

The reason is that with an inside out wall, by design, the insulation being on the inside of the room is now part of your acoustical environment. In that respect it is better to use the 703 or comparable or even the rockwool. Whatever is respected as a product for acoustical treatment is what you should consider.

trodden wrote:

Ted White wrote:

Yes, the fluffy (thermal) pink, yellow or white stuff. Recycled cotton, cellulose, and recycled polyester also work well, as does mineral wool. See the NRC data in their IR 693 report http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir693.pdf Perhaps I'm mis-understanding. What I'm referring to are insulated sealed cavities in walls, floors and ceilings. Exposed insulation on the wall or ceiling surface is for in-room reverb control, and you see 703 commonly used.

So mineral wool/rock wool works better than say a 703 type substance within sealed walls. Good to know, cause its usually cheaper.. but yeah... the fluffy stuff is cheaper than all!

You still haven't quite gotten it - the cheap fluffy stuff is not mineral wool / rockwool (which are the same product ) - rather - the fluffy fiberglass insulation. Mineral wool is more dense than fluffy fiberglass (it's actually very close to 703/705 when comparing density) and you get your best bang for the buck with the fluffy fiberglass........ the recycled products in the same density range are equtable - but are typically much more expensive than the standard isulation. Rod

rod gervais wrote:

trodden wrote:

Ted White wrote:

Yes, the fluffy (thermal) pink, yellow or white stuff. Recycled cotton, cellulose, and recycled polyester also work well, as does mineral wool. See the NRC data in their IR 693 report http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir693.pdf Perhaps I'm mis-understanding. What I'm referring to are insulated sealed cavities in walls, floors and ceilings. Exposed insulation on the wall or ceiling surface is for in-room reverb control, and you see 703 commonly used.

So mineral wool/rock wool works better than say a 703 type substance within sealed walls. Good to know, cause its usually cheaper.. but yeah... the fluffy stuff is cheaper than all!

You still haven't quite gotten it - the cheap fluffy stuff is not mineral wool / rockwool (which are the same product ) - rather - the fluffy fiberglass insulation. Mineral wool is more dense than fluffy fiberglass (it's actually very close to 703/705 when comparing density) and you get your best bang for the buck with the fluffy fiberglass........ the recycled products in the same density range are equtable - but are typically much more expensive than the standard isulation. Rod

Thanks Rod. Yeah, I worded my post all wrong. Familiar with mineral/rock wool. I have found it to be cheaper than say 703 or whatever the johns manville equivilent... but was meaning that the "flufffy" stuff you get at home deSpot is definitely the cheaper of the three. I have found, in the case of making treatment panels that the rigid fiberglass being the "easiest" to work with due to its "stiffness".. while rock/mineral wool can be a bit "floppy" and not hold an edge as well. Buy as you said, both are close when it comes to density. So its up to whether or not i choose the inside out wall vs. the standard wall to determine what i'll choose (regular insulation vs. rigid/mineral/rockwool. If I do go with "inside out", How are people keeping the insulation in place? I'm guessing the fabric facing attached to finish off the wall does a good job in keeping where it needs to be as well as how "snug" it sits between the framing.