Detached two-story garage isolation

[larged817]

Hi all,

I am a proud new owner of a two-car, two-story detached garage (26' x 22') in Chapel Hill, NC. I plan to use this existing structure as a practice facility for the various bands I am playing in. The type of music generally ranges from heavy metal to blues rock to prog, and the loudness has peaked at 107 dB in some of my recent measurements. The bass guitar runs through a 600W Mesa, and one of the drummers is a pretty heavy hitter.

I need to build a room on the first floor of this garage capable of containing the noise and keeping neighbors happy, etc. The good news is the property is in the woods, with plenty of trees and shrubs around the garage. However there are two neighbors, one house 50' to the west and another one 100' to the north, across the street. The garage door faces east. The floor plan here shows the positions of windows and doors.

I also do some recording but at this moment I must emphasize that I am primarily interested in just having a place to practice. Eventually I would like to convert the upstairs into a control room and mastering suite but I must focus all my efforts on isolation first so I don't run over budget...speaking of which I have about $5000 USD to put into this first floor jam room, although roughly half of that will have to go into the mini split and HRV systems. Along with this limitation, I also wish to keep the existing garage as is, only building "temporary" partition walls that can be removed should I ever decide to sell the house. The existing walls consist of 2 rows of cinder block on a concrete floor, and then standard insulated 2x4 stud walls with 1/2" interior drywall, and ~1/2" exterior wood siding.

I am aware that the ~70 dB of reduction I need may be unobtainable with these limitations, but I would like to try to maximize the transmission loss of this structure the best I possibly can. My current idea is to build a room with angled walls, resting the stud frames on top of neoprene strips as shown in my floor plan. Then I would like to use Genie Clips and hat channel to float a double layer of 5/8" drywall as the final inside leaf. The cross-section image shows the general idea, but after doing some of the "required" reading on this forum, it seems like this is a poor design; I may be building a 3- or 4-leaf system. Furthermore, what I'm gathering is that by floating the inner stud walls, and floating the drywall with Genie Clips, I'm allowing the stud wall to develop it's own resonant frequencies that will escape my isolation attempts.

My initial questions are:

Are the Genie Clips necessary? Should I just ditch them and mount the drywall directly to the studs, so the whole mass is resting on the neoprene strip on the floor?

In the existing walls, there is a 4" shelf above the 8" cinder blocks since the wall is only 4" thick. Would it be useful to add mass in this space, such as more drywall or possibly even brick and mortar?

I currently have no plans for the ceiling since there is a whole finished room on the second floor that I do not mind bleeding sound into. Will noise still bleed through this room and escape through the roof? I figured I can add ceiling treatment if necessary after the walls are built.

Will it help to decouple the low frequencies by building a 4" drum riser resting on neoprene U-channels? I figure I can set the bass cab on this riser as well.

I have additional questions about flooring but I figure those can come later. As for now, I am just trying to get advice on my current wall plans. Thank you all so much for taking the time to read about my situation; I have already learned so much from this informative and well-maintained forum! Please see the floor and wall plans below:

JLS_3D view.png

JLS_Jam Room.png

JLS_Wall Cross section.png

Cheers,
-Bashtaar

[Soundman2020]

Hi there, Bashtaar, and Welcome to the forum!

sorry for the long delay in replying, but "better late than never", as the saying goes. I just have too much on my plate right now to be able to spend time on the forum, unfortunately.

type of music generally ranges from heavy metal to blues rock to prog, and the loudness has peaked at 107 dB in some of my recent measurements.

How did you measure that? 107 for a heavy metal rock band is very much on the low side. That would normally clock at least ten times higher, around 115-120. Are you sure you had your meter set up correctly, and properly calibrated? What make and model of meter is it? The cheap Chinese toys that you get on eBay for US$ 30 are terrible, and no use at all, so maybe that's the problem?

The bass guitar runs through a 600W Mesa, and one of the drummers is a pretty heavy hitter.

Even more reason who a peak of 107 dB is not realistic. I suspect your meter, or your setup, or your calibration.

I need to build a room on the first floor of this garage capable of containing the noise and keeping neighbors happy, etc.

You mean "first floor" as in the one that sits on the ground, right? Not the one that sits ten feet above the ground

Eventually I would like to convert the upstairs into a control room and mastering suite

That sounds hopeful... in the sense that it implies that your "first floor" really is at ground level, and sitting firmly on the ground....

but I must focus all my efforts on isolation first so I don't run over budget

Then you should include the design of the CR right now as well! Isolation is a system, not "something you can do now that won't ever change even if I build a massive new room right above it". Simply adding that new room above could have a drastic effect on the isolation of the already completed room below. It is quite possible that you cold get great isolation in your rehearsal room right now, then suddenly see it all disappear when you add the CR later.

The point is that even if you don't actually build the CR now, you still need to take it into account fully with your design for the LR (= "live room" = "rehearsal room"). You need to proceed with the isolation plan as though the CR were already there, being built at the same time, even if you don't build it for now. otherwise you could be seriously disappointed down the line...

The reason for this is resonance. Your isolation system depends on resonance to work in the first place, and can also be trashed by resonance. The entire premise for isolating a studio is that the walls are designed to create a resonant system that is tuned to at least an octave below the lowest frequency you need to isolate: If you later add something else to that, you WILL re-tune the entire system, and it is entirely possible that you will re-tune it to a higher frequency, which would destroy your low frequency isolation. So if you had already managed to tame the sounds from your mega-watt bass cab and angry-gorilla drummer such that they did not leave the premises, all of a sudden you could find your neighbors yelling at you and the cops knocking on the door when you do the CR later, simply because you accidentally changed the resonance of your isolation system.

Word to the wise: design the whole facility now, to work together as a complete system, then build what you can afford to build now, and compensate for the "missing" parts.

speaking of which I have about $5000 USD to put into this first floor jam room, although roughly half of that will have to go into the mini split and HRV systems.

Ummmm.... Nope. Not going to happen.

Sorry to be so blunt, but there's no way you can successfully isolate a 400 square feet studio with US$ 2,500. That means you are assigning just US$ 6.25 per square foot. The installed cost of drywall today is roughly US$ 2.50 per square foot OF DRYWALL. You have about 80 linear feet of wall, probably 8 feet high: 640 square feet, plus 400 square feet of ceiling. Total: 1040 ft2 Cost: US$ 2,600. But that's for a single layer of 1/2" drywall, while you will need at least two layers of 5/8" drywall. So double that, at least.... There goes your entire budget, just on drywall, without having any framing, insulation, nails, caulk, flooring, doors, windows, lights, electrical, paint, acoustic treatment, architects, permits, inspections, ....

To be realistic, you should add a zero to your budget. That would put you in the general ball-park, but it would still be tight.

I am aware that the ~70 dB of reduction I need may be unobtainable with these limitations,

If you wanted to get upwards of 70 dB isolation, you would need to not just add a zero, but also multiply by about 3 or 4. Getting 70 dB is a very tall order. It is possible, yes, but not on US$ 2,500, and not on US$ 25,000 either.

Most home studio builders are very happy to get isolation about a hundred times lower than that, at around 50 dB. That is do-able on a 25k budget for that size space, if carefully designed and carefully built, assuming you do all the work yourself, and have access to good discounts on building materials. If you get a contractor to do it and/or pay normal Home Depot prices, then you'd need to go even higher on the budget.

My current idea is to build a room with angled walls,

Angling your walls increases complexity, and therefore increases costs.

resting the stud frames on top of neoprene strips as shown in my floor plan.

You don't have enough money in your budget to do that, but fortunately you do not even need to do that anyway, even if you had a budget ten times the size. Here's why:

http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

That's about floating floors, but the exact same applies to floating walls: You do NOT need to do that. It is a myth. Not to mention that a roll of suitable 1/2" long and wide enough to do your walls would cost about US$1,500
- more than half of your entire budget...

Then I would like to use Genie Clips and hat channel

Have you checked the cost of genie clips? They cost about US$ 5 each. A box of fifty costs around US$ 250. For a thousand square feet of drywall, you'd need about 5 boxes: That is half of your entire budget,,,

what I'm gathering is that by floating the inner stud walls, and floating the drywall with Genie Clips, I'm allowing the stud wall to develop it's own resonant frequencies that will escape my isolation attempts.

Possibly, yes, but that would not be a problem if you design the entire system correctly such that your final resonant frequency (the highest one) is at least an octave below the lowest frequency you need to isolate.

Are the Genie Clips necessary?

Assuming that the complete inner-leaf framing will be fully decoupled form the rest of the building, then no, you do not need them: But if the inner-leaf framing would be attached to the outer-leaf at any point (apart form the floor), then yes, you do need them.

Should I just ditch them and mount the drywall directly to the studs, so the whole mass is resting on the neoprene strip on the floor?

You do not need the neoprene (see above), and the drywall must NEVER rest directly on the slab, under any circumstances, wither with or without clips. The correct way to drywall a studio is to put shims under the place where the drywall will go, rest the drywall on that, nail or screw it in place, mud and tape as needed, then pull the shims out and caulk the gap. You do that for each individual layer of drywall, one at a time, and that's in addition to the caulking you already did when you put down the sole plate, so you have multiple seals where the wall meets the floor.

Would it be useful to add mass in this space, such as more drywall or possibly even brick and mortar?

Drywall: no, because there's not enough mass in it to be useful here. But plastering with a mortar mix would be good. Make it thick.

I currently have no plans for the ceiling since there is a whole finished room on the second floor that I do not mind bleeding sound into.

Then you will be wasting all of your money, since you will have no isolation at all. See my very first comment above.

Basically, what you are saying here is: "I am going to build an aquarium for my fish, but I'm not going to put any glass on the back, since at some point in the future I plan to put up a window behind it, and I don't mind a little water leaking out the back in the meantime...". How well do you think your fish tank will hold water? Exactly as well as your studio-with-no-ceiling will hold sound...

Will noise still bleed through this room and escape through the roof?

Yes. And not just through the roof... think about it....

How do you intend to support the tops of your inner-leaf wall if you do not plan to put a ceiling across them? You can't just leave the top plates floating around in mid-air, and you also can't attach them to the existing building in any manner at all (see above), so what is your plan for stabilizing them?

Will it help to decouple the low frequencies by building a 4" drum riser

YEs, very much, if you build it properly.

...resting on neoprene U-channels?

That's not built property! Same reasons apply as for floating a floor, as above.

Also, the main purpose of the drum riser is not to stop low frequencies getting into the slab (since they will be airborne in any case), but rather to prevent impact noise and vibration from getting into the slab.

I figure I can set the bass cab on this riser as well.

Yes, but a riser for a bass cab would be built differently...

Overall, I'm not trying to trash your hopes or insult your plans: I'm just pointing out reality in the simplest, most direct way possible. No sugar-coating, no beating around the bush. I hope you take it in the same spirit it is intended: to prevent you from making an expensive mistake. The sad news is that on a budget of 2.5k, you'd be wasting your money, as it would not even go one tenth of the way. For that budget, you might be able to put up a single layer of 1/2" on a 2x3 frame, and maybe have a thin layer of insulation in the stud bays... you might get 30 to 35 dB of isolation like that, perhaps even as much as 40 or so, if your existing walls are in great shape, perfectly sealed, sufficiently massive, sufficiently damped, and if you get very, very lucky. But that's a long, long way from 70.

And your plan does not even show how you plan to seal of and beef up the garage door, which is by far the weakest part of your entire plan. Unless that is sealed off with the same surface density as the rest of the outer leaf wall, are bets are off.

I would seriously suggest that you need to re-think your budget, and/or your goals.

- Stuart -