Small 2 room studio in house needs wall construction advice

[Hepcat62]

I've been lurking here for a while, and I'm finally ready to start finalizing my plans for construction and get building. Here's a quick sketch (pardon the horrible quality) of the floorplan of the 2 rooms I'm dealing with. The blue areas are closets.



The upper room is 8x11, and the lower room is 11x11. Both rooms have 8 foot ceilings and wood floors.

I would like to use the larger lower room as a control room, and the upper smaller room as an all-purpose recording room (drums, vocals, guitar, bass). My problem lies in how to to treat the shared wall, and how to install a window with adequate isolation.

The existing wall is standard 2x4 framing, with one layer of drywall on either side. The wall is not load-bearing, meaning I can modify the existing wall to add the window. The problem is, I am puzzled as to what the best way to achieve 2 separate bases to mount each piece of window glass on is. I'm on a budget, so although tearing out the wall and building a better one is an option, I'd rather not pursue that route. Also, there may be a problem because that wall actually extends past the boundaries of the upper room, and out into the hallway. What's the "best" way to approach this?

As for increasing the isolation between the two rooms (window aside, for the moment), I'm current planning on installing 703 insulation in the wall, followed by a layer of fiberboard, a layer of SheetBlock (limp mass vinyl), and then a layer of drywall. This would be repeated on either side of the wall. I do not really have the room height available for worthwhile ceiling treatment as far as I can tell. I'm planning on building my own doors out of 2 sheets of fiberboard (different thicknesses) with a layer of SheetBlock in the middle, and then thick weatherstripping all aroudn the door and frame for a seal.

I'm not at all concerned about the noise getting out of the house, my neighbors are cool with it, and are far enough away. I'm mostly concerned about my ability to not have conversation and monitoring in the control room end up on the mic in the recording room, and also being able to monitor at least reasonably effectively (even when recording drums or loud amps). I plan on building an isolation platform for putting drums on while recording. Given all of this, how good is "good enough"? I'm afraid the answer will be, "there is no 'good enough', it's all or nothing"...

Thanks in advance,
Brian

[knightfly]

First, if you're on a budget you shouldn't be thinking about Sheet Blok, it's only a little more expensive than platinum. An extra layer of sheet rock costs several TIMES less for about the same performance.

I added a couple of things to your drawing, showing a second wall - what I would do is this: remove the wallboard from the side of your dividing wall that faces the larger room, add your 703 in the stud cavities, put an extra two layers of 5/8 sheet rock on the side toward the small room - then, put up a steel stud partition parallel to the existing window wall, frame in dissimilar thickness glasses in each wall frame, put two layers of 5/8 sheet rock on the OUTER side of the new steel frame, seal the new frame against the old wall with closed cell foam and acoustic rated caulk at both ends. Make sure not to let the new wall frame touch the old one except at the ceiling and floor - use Sill Seal (Home Depot, pink foam stuff on a roll) under the bottom channel of the new frame, fasten the top of the wall to the existing ceiling and caulk well with acoustic caulk.

The three layers of drywall on one side on wood studs will help low bass Transmission Loss, and the two layers on the steel studs will take care of mid-upper frequencies that get through the first leaf of the wall.

For the glass, use as close as you can get to 1/3 the glass thickness in each half of the wall as the sheet rock total for that side. In other words, if there are three layers of 5/8 sheet rock on the one side, the ideal glass thickness would be 5/8" - for the other, new steel stud side, if you use 2 layers of 5/8 sheet rock for a total thickness of 10/8", then one third of that would be about 3/8". Each glass should be bedded in neoprene and framed in as far from its counterpart as possible (maximum air gap), sealing with aquarium sealant after thorough cleaning. Handle with white cloth gloves after cleaning so you don't end up with permanently dirty glass. Wrap some of your 703 in black cloth and fit it between the two wall frames, surrounding the glass area - this will let the area between the glass "bleed off" the lower frequencies between the two walls.

Glass is expensive, the better it is for studios the more expensive it is. Cheapest is plate, then tempered, then laminated. Laminated gives 2-3 dB improvement over plate, and plate may not meet code next to an operable door. If you can't afford that thick a glasses, go with the closest you can. Those thicknesses will come as close as you can get to equal performance with the wall itself.

Hope that helped some, I'm out of steam for the night (3:30 am)

Here are a few links that may help explain construction with drywall/steel -

http://www.usgaction.com/handbook/toc.htm

http://www.usg.com/Design_Solutions/2_3 ... ontent.asp

Gotta run for now, give this some thought and I'll try to explain anything I may have missed this time around... Steve

[Hepcat62]

Steve,

Thanks for all your help! You obviously spend a fairly ridiculous amount of time replying to all of our questions.

Here are some concerns/questions I had about your suggestions.

- The way the doors into these rooms should open because of space constraints seems to make it impossible to add an inner wall on the side of the larger room as you had suggested, because I'd then also need an inner door. For the inner door to work, the outer door would have to open out into the hall, correct? That would make entering/exiting the recording room a real pain... That's why I was leaning towards thicker doors with he SheetBlock, as opposed to double doors.

- The reason I was looking into SheetBlock was because of its low thickness/performance ratio. There's not a huge amount of space between the existing wall in the smaller room and the door frame for the room. So my plan was to tear down the drywall, replace it with a layer of MDF (or similar), then add SheetBlock and an extra layer of drywall. Of course, that causes problems with mounting the window...

- ... So I was thinking of building an extension out of the wall on the side of the larger room, like this, to mount the control-room-side glass on.



This would be a floor to ceiling unit (or at least floor to 6" above the window), built separate from the wall, and caulked and sealed with the wall/floor/ceiling surfaces. There would be a sill attached to the wall and extending beyond the wall on the recording room side, in order to mount the bottom of the glass as close to the exterior of the wall as possible, with the top end of the glass extending into the room. This would allow me to use at least the insulated space within the wall to try and absorb some of the low-frequency stuff.

I like the aesthetics of it (it would probably end up being wide and trapezoidal) assuming it's finished nicely (maybe nice stained hardwood), but am I completely out of my mind in thinking it has a snowball's chance in hell of working out isolation wise? I won't be at all surprised if I am. I know it's not ideal isolation-wise, but I'm wondering if I could get "good-enough" with something like this.

Just some crazy thoughts, and thanks again for all your help!
Brian

[knightfly]

Sorry, Brian - I marked up your drawing and then forgot to attach it - Duh...

What you're suggesting is close to what I envisioned. Since I didn't have exact dimensions available, I wasn't sure what you could get away with. My idea is to parallel the existing wall for the entire distance it's coincident with the other room - this will give you much better isolation than a single framed wall, no matter how much "platinum" you used in the single frame wall.

When you're deciding what kind of materials to use in a wall, don't fall into the trap of making both sides IDENTICAL. Sound passes through a wall "leaf" the easiest at its RESONANT frequency, so if you make both leaves of the wall the same mass, you will run the risk of having one particular frequency pass through the wall. Very disturbing...

Also, I wouldn't bother tilting either glass unless you can't control LIGHTING reflections without it - the effect on acoustics is minimal and can actually decrease TL by narrowing the available air gap. Just be sure to absorb the surround, so the space between glasses can vent between the wall leaves.

If you worry about getting TOO good isolation, you'll most likely just get frustrated by flanking noise caused by continuous framing/siding between the two rooms - however, doing a parallel frame wall for the entire coincidence of the two rooms, if it's doable, would be worth the effort... Steve

[Hepcat62]

Ah, ok. That makes MUCH more sense, and seems very doable. I think that's the approach I'll take. So to clarify, both walls would be packed with 703, correct? Also, would I be ok with only one extra layer of drywall on the smaller room wall? I think that's about all the room I can spare over there, without making the door slam into the wall when opened. I could put 3 layers on the side of the larger room without any problems.

Thanks,
Brian

[knightfly]

Brian, that should work fine. It doesn't matter which side gets which, just so they are NOT the SAME mass. If you don't want to spend quite so much on 703, you could use 3" 703 in one frame and use the regular fluffy fiberglas in the other. If you do that, you can install the fluffy stuff so it pushes against the wallboard from the inside, which will slightly damp that leaf. Damping reduces ringing at resonant frequency, which will improve the Transmission Loss at that frequency, which just happens to be the MOST likely frequency to leak through...

Remember to also reverse the order of the glasses - you want to match each leaf with an equivalent mass per square foot for best results... Steve

[Hepcat62]

Ok, cool. One last question (for now at least) - do you have any suggestions for how to construct the soft joints with the existing wall? Should that be nailed to the ceiling and floor, but then just caulk the seam with the existing wall? Or would it be better to use a rubber or closed cell foam seal there?

Actually, one more... How far out from the existing wall you recommend that I build the new wall? I was thinking that the exterior of the new wall should be maybe 6" from the existing wall? Is that overkill, just right, or not enough? Obviously I'd like to keep it as small as possible while still being effective, so I don't lose too much square footage in the room.

Brian

[knightfly]

Closed cell foam would work, but you would probably have a harder time getting enough compression at the middle of the joint to make it seal well. It would be better to get some acoustic rated caulk,build the frame within 1/4 to 3/8", then caulk heavily on both sides of the joint.

If you have at least a two inch gap between frames, that would work. Comes out about what you said, when measured to the outside. More air gap is better, but your limitation will probably be glass, flanking, mass, and air gap in that order. If you were shooting for higher isolation and had a physically separated room it might be worth allowing more air... Steve