looking for some advice on small warehouse studio

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Hi. First time poster here. Currently in the middle of building a small studio space inside a warehouse and looking for a little advice.

The space: 53'x33' warehouse with concrete floors. The ceilings are 14ft but there is a structural beam running the length of the place, right in the middle, hanging down 4 feet from the ceiling. The west side of the building faces a busy street that has a lot of truck traffic. See attached image - not exactly to scale, but close.

The second floor of the building is a rehearsal space with 2 rooms. One of the rooms (indicated as upstairs room 1 on the attached diagram) is used fairly frequently and the other (room 2) not as much.
As far as i understand, there is a concrete slab in between the 2 floors but no insulation.

what i have done so far: We have built the control room, which is roughly 12x14 with a 9' ceiling (i had to keep the ceiling low in order to get under the aforementioned beam). This is located at the west end of the space, right by the busy road. This was built with a staggered stud wall that is sitting directly on the concrete with a thin foam layer beneath the floor plate. There are 2 layers of 5/8" gypsum on the outer wall and i have only put one layer on the inner wall. I will add a second layer, likely with green glue.

The doors to the control room are solid core wood doors. Double doors leading in from the main space and a single door that leads to the door on the existing outer wall of the warehouse. That door leads to the exit to the street. Hopefully this makes sense! The doors are in place, but have yet to be sealed along the edges or bottoms, nor have they been beefed up in any way.

We have also built walls to create a garage area (which was necessary), which sits directly under upstairs room 1 and about 6 inches from the control room walls. There is one layer of 5/8 gypsum on the outside, but i have yet to insulate and add a layer of gypsum on the inside walls.

The mission now: Now I need to build the live room. Due to a number of factors, i only have one spot i can put the room. What i have to work with is 18'2" x 15'1 and after using a mode calculator i have decided i will likely go with 17'8" x 14'5" x 11.5" as my outer dimensions. Due to the jam room directly above, i think i should go with double walls with double 5/8 gypsum. So, I will end up with roughly 15x12.5x10 inside dimensions. The west wall will be right beside the garage wall (gypsum). The east wall will be right beside the other wall, which is currently plywood. The north wall will be beside a concrete wall. The south wall will have open space in front of it.

The noise from above: I have conducted a test. A punk band was playing in room 1 and it was 113db. At the same time, a guy was playing bass at about 95db in room 2. Downstairs, in my unfinished control room (with door open), it was roughly 62db and standing where the live room will be (directly under room 2), it was about 70db. I hear mostly bass, but also a little guitars and drums. So my plan is to build a double wall room to try and block out the sound of the jam room above. The sound coming out of my space is of no concern at any time.

Other noise concerns: None, really. The sound from the street is almost unnoticeable even with the unfinished garage walls and door. I don't notice any truck traffic rumbling the concrete slab and when standing in my control room in complete silence, i can barely hear any traffic.

My builder friend is ready to come this weekend to start working on framing and i have a couple specific questions that i can't find answers to.

1) How much of an air gap should i have between my two walls? I read some people have as little as an inch and some go with more. For obvious reasons, the smaller the gap the better for me.

2) How much of an air gap do i need between the outer walls of my room and the existing walls next to them (garage and future iso room)?

3) is it an issue that all the existing walls that i am building beside are of different materials?

4) is there anything else i should be concerned about?

Thanks in advance to anyone who can help here. In a perfect world I would just have a professional design this thing, but for budget reasons, this has to be a DIY project.

[gullfo]

welcome!

in most cases, i live room doesn't necessary benefit from the same ratio treatment that a critical listening room does. asymmetry can be very useful in a live room - patches of walls with different harder materials for drums, softer for vocals, etc.

in general, the "air gap" is the measure between the layers of mass (drywall, plywood etc). so if you leave a 1" gap between frames on a 2x6 wall, you have an air gap of 12"... and since the air gap will be loaded up with the insulation (for a frame like this i'd put in R30 batts and compress them to fit (i.e. two layers of ~8" insulation pressed down to 12").

similar situation for the ceiling - if you're able to put in a framed "inner" ceiling using 2x10 or 2x12 (more likely), then 2x R49 in that space. line the room with 1/2" plywood or OSB, then 2x 5/8" type-x drywall. the plywood adds bracing and a nailing surface. note that its likely you'll need isolating sway braces to support the room and ceiling - Mason Industries and Kinetics Noise have what you need.

as far as different structural materials - depends. a masonry wall will be a different set of design than a wood frame, and a metal frame would be different from that - and depending on your floors ability to support 8-10 tons of new room as well as a secondary ceiling frame, plus equipment and live loads... probably ok as its a garage but sometimes the middle of concrete pads don't have the same support versus the edge of the pads. so you should have a structural engineer check it.

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thanks for taking the time to answer, Glenn. I probably left out some detail which may be relevant and I have included another diagram.

in most cases, i live room doesn't necessary benefit from the same ratio treatment that a critical listening room does. asymmetry can be very useful in a live room - patches of walls with different harder materials for drums, softer for vocals, etc.

interesting, and good to know!

similar situation for the ceiling - if you're able to put in a framed "inner" ceiling using 2x10 or 2x12 (more likely), then 2x R49 in that space. line the room with 1/2" plywood or OSB, then 2x 5/8" type-x drywall. the plywood adds bracing and a nailing surface. note that its likely you'll need isolating sway braces to support the room and ceiling - Mason Industries and Kinetics Noise have what you need.

i should have been more clear on this. My plan was to build the 2 walls and have separate ceilings, each resting on their own walls. The plan was to have 2x 5/8" drywall on all walls and ceilings.

as far as different structural materials - depends. a masonry wall will be a different set of design than a wood frame, and a metal frame would be different from that - and depending on your floors ability to support 8-10 tons of new room as well as a secondary ceiling frame, plus equipment and live loads... probably ok as its a garage but sometimes the middle of concrete pads don't have the same support versus the edge of the pads. so you should have a structural engineer check it.

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i was planning on using two 2x4 wood frames. i was more concerned if the existing walls i need to build beside matter much to me. As you see in the diagram, one is gypsum, one is plywood.
As far as the support capability of the slab, i will check into it. The upstairs tenant knows the last 30 years history of the building, and if i'm not mistaken, a 5 or 10 tonne truck was parked in roughly this same spot for some years.

Again, thanks for taking the time to look at this and if the new info changes any advice you have given so far or sheds any new light, please let me know.

roomDetails.jpg

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i just noticed that in my diagram, the joists would appear to me running lengthwise. But they will be running the proper way! Sorry, i have not yet learned to use Sketchup.

[gullfo]

with the extra space above, i'd not stagger. once you add in a layer of plywood/osb - that will help with the rigidity and a nailing surface + 2x 5/8 type drywall + electrical, AC, lighting, treatments, i'd recommend moving up to 2x6 or incorporate 4x4 posts into the 2x4 wall. definitely do not waste the opportunity to NOT stagger though, staggering is when you don't have an extra 2' above the exterior ceiling... just makes the construction harder and you'll need to drop HVAC etc so having the joists in both ceilings will make that much easier.

some references: https://www.awc.org/codes-standards/spantables

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thanks again, Glenn...good to know on the ceiling...my builder likes that plan!