Bracing Needed to Stabilize Room within a Room?

[Matt C.]

I'm planning on building something resembling a room within a room in my garage, to be used as a live room. The room will most likely not have an independent ceiling (so not a TRUE room w/in a room), but the four walls will be connected only to the slab and each other. The dimensions are roughly 17'x22', probably 10' high. I was planning on doing typical 2x4 walls with two layers of 5/8" drywall.

Question is, do I need to install some type of isolating sway braces (something like the WIC clips from Mason Industries) to stabilize the framing of the interior room, or will the walls will be rigid enough by themselves?

Thanks for any advice!

[Gregwor]

Why can't you do a true room in a room? Build the ceiling out of LVL stud. For a 22' span you can easily get away with sistered 7 1/4" x 1 1/2" LVL stud as your skeleton. Do an inside out ceiling which will provide you with the ceiling treatment you need while still maintaining almost all of your ceiling height (acoustically)!!! For the amount of isolation you'll gain, the extra money on the engineered studs is well worth it!

Also, no matter what, your walls should stand up nice and strong and require no bracing once the walls are joined together to make a square. The ceiling will only further add to it's integrity.

Greg

[Matt C.]

Thanks, good to know. A true room in a room is a possibility, but I'm still on the fence about it. The added complexity might be more than I can deal with. My thoughts being:

- Framing is pretty new to me. The walls will be straight forward enough, but a ceiling seems more challenging. And I haven't found great detailed drawings of this sort of independent ceiling, so it's a bit intimidating.
- Isolation between this room and the 2nd floor above it is not as critical as isolation from the exterior of the building. I know the independent ceiling will give better isolation, but I'm not totally convinced it's necessary in this case. My thought was resilient channel and two layers of drywall on the existing joists would probably be adequate.

[Gregwor]

The added complexity might be more than I can deal with.

The ceiling really is no more complicated than the walls. If anything, it's actually easier because you don't need to have specific framing protocols regarding king studs and things like that.

a ceiling seems more challenging. And I haven't found great detailed drawings of this sort of independent ceiling, so it's a bit intimidating.

I have some pictures saved on my recording computer that I can share if I remember to! PM me if I forget to post them for you. I saved them off of another post that Stuart (Soundman2020) had posted on. It shows the real benefit of inside out ceilings. Basically though, you just use the LVL stud to build a sort of skeleton and then build smaller modules out of normal dimensional lumber that has drywall (or OSB then drywall) on top of it. Sealed of course! Then, slide the module into place, screw it (horizontally) into the LVL skeleton and stuff it with insulation. Then cover that with fabric and you're done!

Isolation between this room and the 2nd floor above it is not as critical as isolation from the exterior of the building.

Sound doesn't quite work the way you're describing it. Think about it this way. Say someone is blaring music in their car with their windows up. You're still going to hear that low end for a good distance... like when a car drives by your house, you still hear the booming bass. Now, say you're standing on the passenger side of the car. The driver opens their window. You hear the high end, and of course the bass even though you're standing on the other side of the car. THAT's how sound works. It goes everywhere, and it escapes through the easiest path.. the weakest link in your system. In your case, that weak link will be the ceiling. And because the vibrations of the drywall will be transmitted directly into the structure of your home, your home essentially becomes a bit speaker cabinet. Your home will then transmit the sound directly to your exterior.

My thought was resilient channel and two layers of drywall on the existing joists would probably be adequate.

Resilient channel does NOT provide good isolation at the problematic low frequencies well. Also, it's very common for people to short circuit the system while installing drywall at which point the entire thing is wrecked.

Long story short, if you're building your walls as two leaf systems due to your need for high levels of isolation, then don't waste your efforts by cutting corners. Build a proper decoupled two leaf room with an inside out ceiling.

Greg

[Matt C.]

Thanks for the reality check, I'll start planning a proper ceiling. I'd love to see whatever pictures you've got. Part of why I thought a ceiling would be complicated is I didn't think I'd be able to get single pieces of lumber long enough to span the whole room, but I see now that those are in fact available.

[Gregwor]

Here's the thread where I found the real life pictures. It'd take me a while to find the SketchUp versions comparing a normal ceiling to an inside out one so maybe I'll just post them myself.

http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=21165

Greg

[Gregwor]

So there is a series of pictures, but these two clearly show the benefit of doing inside out, even against an interleaved ceiling (where the ceiling and floor above joists are weaved in one another). Also, the series of pictures show how having the interleaved joists prevents having much, if any, space for insulation or duct work. Yes, it's more money. Yes, it's more work. But the pay off is huge and makes it all worth it.

Here, it is interleaved. You can see the ceiling joists are stuffed up inside the floor above's joists, leaving no room for a nice spring gap stuffed with insulation. Also, it shows that in order to properly acoustically treat the ceiling, you will need to build and mount acoustic panels. And the panels in the picture don't fully cover the ceiling or the corners where it is really needed. Realize how much work it would be to frame these panels and mount them. The cost of building those right there negates the argument to build it this way instead of inside out!

CEILING--interleaved--S02-.png

And here is the clean and amazing inside out system. Of course, you'd need to cover it with fabric, but you can clearly see it's superiority in every aspect.

CEILING-Inside-out--S02 500KB.jpg

Greg

[ZSXI]

@Gregwor

Regarding the inside out ceiling -- am I right in thinking this would fulfill the requirement for any kind of cloud over the mix area? What's the typical joist size for this, 2x6? 2x8? I'm going to be building a shell in a 9' room and want to preserve as much height as possible. This looks like a great solution.

[Gregwor]

am I right in thinking this would fulfill the requirement for any kind of cloud over the mix area?

For mixing. . . . sort of. It will certainly dampen as intended, but at mix positions, it's common for clouds to be angled such that the hard back on them deflect sound towards the back of the room (where there is more treatment).

What's the typical joist size for this, 2x6? 2x8?

You will probably need to use LVL stud, not dimensional lumber. Google LVL stud and find a manufacturer near by. Or drive by some new home development areas and look for the brands on their lumber. From there, you can contact the manufacturer and get some distributors. Internally, the distributors often have engineers in their building who can give you their stamp of approval (they did mine for free!) so that when you get your framing inspection done, you're good to go. You need a stamp of approval for engineered wood.
To answer you question a bit more, obviously we don't want to eat up too much ceiling height. For my control room (just over 19' wide), I had to use sistered 1 1/2"x7x1/4". I told the guy I would have upwards of 50 pounds dead load and live load (hanging my angled clouds off of it along with the drywall and insulation). He responded that I could literally hang a V8 engine off of it and be safe.

So, in conclusion, yes, visually, you won't have a 9' ceiling, but acoustically, you'll be close. And let's face it, we're audio nerds, and audio comes before visual.

Greg