FINISHED IN 2020! Sharward's Partial Garage Conversion

[sharward]

Renamed from "BACK IN ACTION IN 2018! Sharward's Partial Garage Conversion" on 2 July 2020...
Renamed from "Rehearsal Studio Plan - Partial Garage Conversion - Advice??"...
Renamed again from "Sharward's Rehearsal Studio Plan - Partial Garage Conversion" on 27 November 2005...

Hoping for some advice. Bought (kind of) new home last Spring w/ very spacious 3-car (tandem) garage, with intent to build a rehearsal studio in rear left corner. I plan to play my drums loud and eventually have band rehearsals/writing sessions in this space. Some amateur recording may occur in the future.

Left half of garage is about 38' deep -- about 8' deeper than right side. Width of left side is about 10'. Perimeter of build space is about 10' x 17.5' with no vents, windows, doors, or access panels on the existing walls of that space. When the studio is built, there will still be 20' of clearance on left side to acommodate a vehicle on that side -- two cars will fit side-by-side towards the front of the garage.



Goal:
Expecting to generate 110dBA and hope to achieve outside levels of 40dBA, requiring STC of 70. Local noise ordinance requires no greater than 50dBA. Definitely need to stay under legal limit and not disturb neighbors. Nearest neighbor is 10 feet away (their garage is inverse configuration as mine -- about 38' feet deep on right side). We're the "new guys on the block."

Challenges:
High STC rating required. Limited overall width of space. Very cost conscious (but not "cheap"). Garage door remains intact so cars can come and go (considering replacing door with one of better quality).

Existing Construction:
Left wall is uninsulated 4" with 5/8" unfinished gypsum on garage side and stucco on exterior side. Existing rear wall is insulated 4" with 5/8 unfinished gypsum on garage side and finished 1/2" or 5/8" textured gypsum on interior side (office). Existing 8' long wall on right is same as rear wall (laundry room). Ceiling is just over 10' high, 5/8 unfinished gypsum on garage side, no insulation -- attic space above. Floor is concrete with expansion joint around entire perimeter of garage.

Preliminary Plan (High Level):
"Room within a room" w/ 2 doors (one swings out on outer wall, other swings in on inner wall). HVAC: Planning to use ductless system, such as Mitsubishi's Mr. Slim line, exterior unit at back of house, about 30 feet and 3 rooms away from garage.

Questions I have

Should I plan to rip off the existing gypsum, then insulate those walls, and leave them uncovered (since there will be another set of walls erected alongside of them? (I'm thinking probably so, since I assume I don't want three wall "skins" so relatively close together, due to risk of resonance.)

Should I / will I need to invest in an insulated garage door and/or a better quality side access door? These doors are not actually connected to the studio space, but they're might be the last chance to catch sound leakage. Existing doors are cheap quality but servicable.

Studio doors -- what should I use? 36" wide preferred. Location of door marked in photos with the fire extinguishers. Anything I can/should do to reinforce the doors (i.e., sand, extra layer of material added to one side, such as plywood, etc.)?

I'm really unclear on how to go about ceiling... Should I (a) Partition the "inner" walls all the way to existing ceiling, then string new ceiling joists across the new "inner" walls; or (b) string new ceiling joists across the existing "outer" walls and the newly constructed "outer" walls, then partition the "inner" walls up to the new ceiling; or (c) something else entirely?

Whatever the answer to the above question, how do I hang the ceiling and anchor the walls in a decoupled manner?

Is the "expansion joint" around the perimeter of the garage sufficient "decoupling" of the floor? Or should I do some kind of floating or raised floor?


Sorry I don't have any fancy CAD drawings. I have hand-drafted some designs, but they're no longer valid after all my research. I've learned so much -- lots of it right here too!

Looking forward to your comments, questions, and input... Thanks so much!

[knightfly]

Been trying to catch up on my own life for a few days, and have about 18 posts to answer so I'll have to keep this first one kinda short;

First, forget STC - for what you want, low frequency TL will be the deciding factor. This can ONLY be accomplished (especially with your width limitation) by sticking to the "2-leaf" rule, which means removing your inner gypsum from walls, beefing up the outer leaf from the inside, and building a second, independently framed, floated room.

At lower frequencies, the threshhold of human hearing is around 55 dBa - so, if you're generating 110 dBa, you'll need about 50 dB MINIMUM TL at 50 hZ - this isn't easy but you can get close by using your removed wallboard as inserts between studs and against your outside sheathing - two layers of 5/8 against the sheathing between studs, CAULKED fully with NO AIR GAPS between outer sheathing or between layers, then fully insulated air space, then insulated inner stud frame, then 3 layers of 5/8 wallboard, will give about 45 dB TL at 50 hZ, which means that sounds around 100 dB will just start to be audible on the outside wall.

Ceiling - I need to know EXACTLY (sizes, materials, spans, etc) how your roof is built, including ceiling joists dimensions - you may need to beef up the ceiling joists where they pass over your space, because here again you'll need 3 layers of 5/8 wallboard for your OUTER leaf (I'm assuming your roof is vented, so can't be considered part of the soundproofing - even vented, it will detract a bit from your two FUNCTIONAL leaves so they need to be heavy)

Once the outer ceiling leaf is solved, the inner will need to be floated on the inner walls, which need to be resting on a floated floor. If you do a search on floated floors, Aaron's thread (many pages) will come up - see what you can learn about mass, m-a-m resonance, etc, and be prepared to put some $$$ into this part - for your requirements, I wouldn't recommend anything less than 3-1/2" of CONCRETE floated on PT 2x6's over EPDM pucks - you need lots of mass, a wide air gap, and high density rockwool fill under the floor if you're to kill things enough to not alienate the neighbors.

Gotta go for now, hope this gets you started... Steve

[sharward]

Thanks, knightfly, for the great feedback.

The more I learn, the more I discover there is to know!

I will research the attic construction over the next few days, then report back with distance between joists and such. I think (hope? ) that they're trusses. And, yes, the attic has small vents in the walls where the eaves pass over them.

I'll be researching floated floors as you recommended. I admit, this is one of the areas in which I have the least knowledge.

If anyone else has any ideas, or if you (knightfly) have anything else you'd like to add when you come up for air again, I will be most grateful!

[sharward]

I popped my head into the attic today. The existing garage ceiling consists of fire rated gypsum attached to metal furring channels - unknown what gauge (and I'm predicting you'll need to know that). The furring channels are attached to the joists, which are attached to the bottom chord of roof trusses. The trusses are made of 1.5" x 3.5" lumber and are 24" O.C. (or closer in some spots), while the furring channels are 16" O.C. The trusses run east-west, while the furring channels run north-south. (The front of the house faces north.)

I'm guessing that the metal furring channels were used to mitigate likelihood of cracks in the fire rated ceiling.

Following are some photos I took in the attic above the garage.


Facing east. Distance between trusses is about 24". Distance between furring channels is about 16". Vents are just out of view to left and right. (ENLARGE THIS PHOTO)


Facing northeast. The bottom of the "Vs" is roughly where I will be constructing my north-south wall(s). (ENLARGE THIS PHOTO)


Close-up of metal furring strip. From top to bottom: (1) Underside of fiberglass insulation, which I temporarily lifted to expose the materials. (2) Blown-in insulation, which is throughout the attic above the living space (but not the garage). (3) Metal furring strip to which garage ceiling is attached. (4) Edge of gypsum board - notice the word "flame" is visible in white lettering on red background. (5) Header of wall that separates laundry room from garage. (6) Gypsum ceiling over laundry room -- apparently no furring strips used in this area. (ENLARGE THIS PHOTO)


Top cords of roof trusses. (ENLARGE THIS PHOTO)

My apologies if I'm incorrect or confusing in any of my terminology... I'm still "learning the lingo." I'll also be happy to provide additional details if needed.

While I await your reply (knightfly), I'll continue to read up on floating floors.

Many thanks to you and all for the help!

[sharward]

OK, I just finished reading all 21 pages in Aaron's Floating Floor thread. WOW -- more than a year in the making!

I especially studied Aaron's photos of his floor construction.

knightfly, you mentioned: "...I wouldn't recommend anything less than 3-1/2" of CONCRETE floated on PT 2x6's over EPDM pucks..."

Are there any other options on the table? Although I can afford the headroom, I'm somewhat averse to using so much concrete.

[knightfly]

You can go for less mass in a floor, but will lose isolation at lower frequecies when you do; I chose 3-1/2" because it's easy to use 2x4's on edge for the edge forms while pouring this slab on your floating framework - anything you do to lessen the mass, or narrow the air/insulation gap below it (above the garage floor) will negatively affect your isolation.

People have had fair success using heavy multi-layer plywood, but these days it's just as expensive and NOT as good as concrete... Steve

[sharward]

Thanks for the clarification on the floor. I'll definitely give it deep consideration.

Now, how about that ceiling? I posted some pics (above) and details of my attic space.

You rock, Steve!

[sharward]

Reading, reading, learning, rereading... I think I know what you (Steve) are going to say.

In reviewing the Complete Section - (Temporary "FAQ"), you wrote:

I don't think I would personally feel too comfortable in a room with 3 layers of drywall overhead mounted on ANYBODY's RC - I would personally tend more toward the heavier leaf of a 2-leaf wall or ceiling being mounted solid to the studs, and just putting two layers of 5/8 firecode sheet rock on the RC. It kind of depends on how much isolation you really need, and whether you can MATCH it with your glass, doors, HVAC, flanking noise, etc - if not, it's a moot point at best.

So, I'm thinking that maybe I should put just one additional layer of firecode sheetrock on the existing ceiling (which is mounted to some kind of metal furring strip, as noted in my post above), which is the outer leaf. Then, on my inner leaf, I'm figuring on using 3 layers of 5/8" sheetrock mounted directly onto new joists that will sit on top of the inner walls. And, of course, rockwool insulation sandwiched liberally between the leaves. Bear in mind that I will be able to afford more air space between the ceiling leaves than the wall leaves, so perhaps that will offset some of the lost TL by using less mass in the outer leaf. (Yes?)

I know: illustrations are due here, and I hope to have some after this coming weekend! In the meantime, perhaps you can comment on this concept so I can know if it's sound (no pun intended).

Thanks a million, Steve!

[knightfly]

Yeah, you're on the right track; no need slappin YOU with a wet noodle...

[sharward]

At last, some illustrations I'd like to share for your feedback...

[sharward]

Continued...

[sharward]

In addition to feedback on the above illustrations, I'd like to ask about firestopping -- specifically, where the air gap between wall leaves meets the air gap between ceiling leaves.

I have reviewed Fire stops in walls can provide both fire resistance and sound isolation on the Canadian IRC Web site, which states:

These findings indicate that, from an acoustics perspective, the best way of satisfying the code requirement for fire stopping is to use a double-stud wall with sufficient insulation so that the width of the air space in the wall is 25 mm or less. This approach does not reduce the effectiveness of the sound isolation of the wall assembly, and can actually improve it if the wall cavity is less than full to begin with.

Does this mean that I just have to ensure that there's no more than a 25 mm gap in this area, and that if there is, to just use more insulation around the outer perimeter of the ceiling? Also, I would like to know, if possible, whether this is likely to satisfy my local building department. (I suppose I should ask them, but I'd like to get an idea of how strong the argument can be if they give me any trouble over it.)

Here are the codes that my municipality use:

15.04.060 Adoption of uniform codes.

The following publications are adopted by reference and incorporated in this code, except as expressly amended or superseded by the provisions of this code:

A. The Uniform Building Code, 1988 Edition, and Chapters 1, Div. 1, 7, 11, 49, 55, and 70 of the appendix thereto, as published by the International Conference of Building Officials (amended by this chapter and Chapter 15.20 of this title).

B. The Uniform Plumbing Code, 1988 Edition, including appendices A, C, and D, and the Installation Standards, as published by the International Association of Plumbing and Mechanical Officials (amended by this chapter and Chapter 15.24 of this title).

C. The Uniform Mechanical Code, 1988 Edition, including Chapter 21 of Appendix B and Appendix C as published by the International Conference of Building Officials (amended by this chapter and Chapter 15.28 of this title).

D. The National Electrical Code, 1990 Edition, as published by the National Fire Protection Association (amended by this chapter and Chapter 15.32 of this title).

[knightfly]

Man, first of all I have to say that your drawings are far and above the best drawn, best researched I've seen in the time I've been modding this forum(other than Rick's, and that's his occupation) - I'd probably have a lot more free time if they were all this good, thank you -

I'd like to say that you've just won the "best drawings of the year" award - it's an all-expense paid, 1 week vacation for two in beautiful downtown Vallejo... (the SECOND place winner gets TWO weeks... )

It's 3:30 AM and I've been at this for the last 9 hours straight, plus I don't want to goof up after giving out all those "atta boys", so I'm gonna have to catch the (few) things I'd change in your plan tomorrow; I know you're anxious, but I'm fighting a cold and need my full 5 hours or I get cranky - I'll try to wrap yours up at breakfast... Steve

[sharward]

So, the floor recommendation is 3 1/2" of concrete. As I mentioned, I'm a little turned off of that idea (but I remain committed to doing it, if that's what it takes).

Given that sand is less dense, and therefore, offers less isolation than concrete...

I was thinking... What if I built a very beefy floating frame structure, and then instead of pouring concrete over the top of it (or, rather, hiring someone to do it), actually using concrete bricks on it, with dry sand as a gap filler? I would use bricks similar to these, laying on their sides (so they were 3 1/2" tall and 2 1/4" wide). I would also divide the brick layer of the floor into sections about 3' x 3', with 1 1/2" x 3 1/2" lumber dividing each section. Then, one or two layers of OSB or something on top of the bricks. Another advantage to doing this is that if for some critical reason I had to gain access to the floating floor framing structure, I could do so via the top surface without resorting to using a jackhammer and destroying the entire structure in the process -- I would just have to empty one or more 3x3 cavities of all of the bricks and sand, do whatever needed to be done, then restore it all to its original state afterwards. (Granted, it wouldn't be fun, but it's conceivable that it could be done.)

Each brick costs about 25¢ at Lowe's and includes 16 7/8" square inches of coverage when turned on its side. Figuring on a 9' x 16' room (32,256 square inches), that's about 1,900 bricks, for about $500 with tax. I also figure I might get a better price and/or delivery if I shopped around.

Does the weaker characteristics of the filler sand negate the affect of using the denser bricks? (Is it a "lowest common denominator" thing?) Or would I simply need to do my best to ensure the least amount of sand and the most amount of bricks in the layout?

Another twist on the idea is using more fashionable bricks (like, maybe this red clay brick) in the same 3x3 sections, using wet mortar, and then not covering it with OSB afterwards... I think that would look great, but would not afford the same level of access opportunity.

I hope y'all don't think I'm trying to "creative" my way around physics and tried-and-true solutions here... Rather, I'm trying to apply what I have learned in a way that is compatible with my skills and budget, respecting all those physics laws we all have no choice but to obey. I can't fathom doing the concrete work myself, but I can picture myself doing the brick thing all by my lonesome.

(Note: Looking forward to feedback in response to previous posts in this thread. )

[knightfly]

ON fire stopping - your local building codes department is your best and easiest source on this. It doesn't matter what the IBC or any other document says, if your local bureaucrat says NO - I would recommend simply printing off the canadian stuff and walking into your local BCD with it, and asking point blank whether they allow this for sound proof construction since it's been proven effective; If they say no, there are other ways of fire blocking without degrading the wall performance - 2 layers of sheet rock fastened only to ONE frame and "sliding" on the other works almost as well.

Floor - yes, you can float a "sandbox" instead of a slab, just fill the form created by the 2x4's with your sand, or blocks and sand, top off with sand flush to the top, add floor (2 layers minimum, preferably) and (as you mentioned) you have easier access than using a jackhammer.

Can you restate just your (un-answered)questions so I can cut to the chase? Thanks... Steve