Rehearsal/Recording Studio Build

[Lonnie]

Hi forum contributors. I am planning a rehearsal/recording studio new build at my house in the coming year and I have a lot of questions. The slab and outer shell of the room-in-a-room build will happen fairly soon, but the room within the shell will not be built for perhaps another year. So my goals with this thread are to clear up some of my general questions, and to make sure that my basic outer shell design is designed and built in a way that doesn't hinder my studio (inner room) designs in the near future. Eventually I’ll jump into the proper studio design. Let me also say that even if no one answers these questions, this forum has already helped a LOT!

PROJECT GOALS
--A space where multiple instrument setups can be out at all times for rehearsal (no more setup and knock down every time I want to practice pedal steel for 45 min). I have some bulky synths that I keep for recording, but if they’re not already out, the odds they’ll actually be used are slim.
--A space where my soundcraft board, rack gear, otari 16 track, and mics/stands can remain out and more or less ready to go. The tight footprint of this gear (without room to get around it for patching) is about 8’ by 7’)
--Enough isolation to be able to play a drum kit at midnight without disturbing neighbors in their houses (as close as 20’ away).
--Enough room to record a 6 piece rock band. I don’t need massive isolation between players, and I tend to like a fairly ‘live’ sounding room on a recording. Also, this size group would be fairly rare. 90% of the recording will likely be just me and one other person.
--The best design for mixing, considering all other constraints.


BACKGROUND
--The space will be used daily for solo practice, a couple times a week for band rehearsal. I will record my own ideas here and there. Probably at least a few hours a week, and at times much more.
--I have recorded quite a lot in my house. I use (when I can) three adjacent rooms, totaling about 550 sq ft, 9.5’ ceilings. I have recorded with sofas, books, dining table pushed back. I put up oc703 panels and usually hang a large oc703 cloud over the drum kit. I know it can sound better, but it isn’t horrible acoustically. The isolation from the street, however, is horrible.
--My mixing set up is a poorly treated, 12 by 13 square room. It’s bad. I constantly have to tweak and reprint mixes once I hear them out of the room, something that’s not always easy being a tape based studio.
--I have a 2 channel interface, so I can attempt to learn to use testing software. My recording and mixing setup is all analog, though.


GENERAL FOOTPRINT/INITIAL PLAN
--45’ by 20’ rectangular building footprint, slab on grade. This will be tucked into the corner of the allowable property offsets, so at least two of the sides have to be square.
--Simple front to back gable, 11’ or 12’ plate height, roughly 16’ or 17’ peak height. Working with engineer to keep the vault as tall and open as possible.
--Within the building footprint, the studio room(s) will take up about 30’-35’ by 20’ (well, the inner space remaining after framing). This will leave about 15’ by 20’ for a space that will have a toilet, slop sink, refrigerator, entrance into the building, and then otherwise serve as a sort of storage shed space for my business. This ‘shed’ space will not be conditioned, though.
--The inner music room doesn’t need windows and only needs the one entry door.
--I typically frame all exterior walls with 2x6 studs for greater R value. However, I can see using 2x4’s to preserve space since I’ll be building a second inner room anyway.
--I typically use polyurethane spray foam insulation filling the stud bays, and about 7” deep at the rafters. If other insulation products (pink fluffy, rockwool etc) are better for isolation, I’d love to know and I’ll be happy to use them instead.
--The building footprint could get slightly larger in either direction, but that will only be worth it if it allows for some huge improvement in isolation or acoustics.

I’ll post some general questions soon, but my first question is whether or not the outer shell plan makes sense. Are there any tweaks to the plan that you recommend? Any questions you have for me that may help develop the plan?

THANKS!

[gullfo]

plan your HVAC now. you will be running it 24/7 while the space is occupied, so your house system, unless you can multi-zone it and it has the capacity to exchange fresh air into the space 4-6x per hour, you'll need additional systems. mini-splits DO NOT handle fresh air exchange and CO2 build up in a hyper-sealed / hyper insulated space is fast. as far as life safety - check local building codes for egress requirements and fire personnel access - windows, doors etc.

if you're thinking of vaulting a 20' wide space, i'd recommend sticking with the 2x6 wall frame and appropriate trusses. also, consider any wind strength requirements in the code. the inner rooms can be 2x4 or might need 2x6 is you're load-bearing them with an inner ceiling.

on the foundation - consider separating the slabs - putting your utilities on one, and separating the control and live rooms (iso rooms as well). defintiely the larger rooms will require an inner footing to support the weight. but you'll gain an immediately higher level of isolation if the rooms are wholly seperated via the slabs (think somewhat akin to "floating" the rooms). also keeping vibrations from equipment and toilet etc will preserve the isolation in the live rooms. plan your cabling strategy now.

consider an air lock - separating bathroom/break spaces, control room and live room with an air space which helps isolate, allows access into each space without using another room, keeps smells localized, etc.

for the bare frame - spray insulation will be fine. pay attention to your vapor barrier placement.

the more you plan now, on paper, the less you will suffer later during the build...

[Lonnie]

Thanks for the reply, Glenn.

The studio will be freestanding away from my house. So the HVAC system will be all new and will only serve the studio. I have begun reading advice here on HVAC routing, air changes, noise-reducing plenums and the like. But I still have a lot to learn. If there are any particularly good overview threads, I'd be happy to read them and save y'all from having to repost the same advice.

Regarding egress and structural questions....This project will be permitted and fully engineered.

You mentioned being careful about my vapor barrier. My outer wall starting point is hardie cement lap siding (or maybe cedar board and batten), rainscreen air gap, then zip system OSB (taped and/or liquid flashed), then studs, then open cell spray foam. I may add polyiso between the siding gap and the Zip. What are your thoughts on this assembly regarding both moisture build up and isolation? I see some threads where folks are installing 5/8 drywall in all the stud bays before insulating.

I doubt I will separate the slabs due to cost, but also because I'm not sure I can even have two rooms. If I consider it, however, do the slabs need to be totally separated? If there's a foundation beam planned, can a deep expansion joint help with isolation?

My initial thought was to vault the inner ceiling after reading that more height in a live room is always good. That said, should I instead consider using some of that space for mechanical? I could potentially have a mechanical loft floating above the studio, supported by the outer envelope. This would save space on the slab elsewhere, but would likely bring my inner ceilings down to around 10'6" at the most. Still pretty high, by my standards.

More general design questions so far.....

---I understand the concept of building the two rooms completely free of each other, with not so much as a nail bridging between these two leaves. I see that entrances can be created by essentially building two well-sealed, mirror image doors and door frames, making sure that only fabric bridges them. (Does this count as an airlock, assuming the two spaces are well sealed?). How do I get mechanical and electrical into the inner room without bridging the two leaves?. I believe I read mention that leaving a flexible bend in the electrical wire could suffice...? Does that mean flex duct will also absorb vibration enough to negate any bridging effects?

---With enough space to properly build a room-in-room, two leaf system, is the use of products such as hat channel unnecessary?

---I believe I read that the minimum space between leaves should be about 8". Is that correct? So two wall systems, built normal (not inside out), with 3.5" studs and 1" of space between the walls, should give that minimum 8", yes? If so, I don't fully understand inside out framing. It seems that moving the drywall outboard of the studio space would mean you need to space your two studwalls further apart (1" becoming 4.5"), thus negating the space-saving benefits. But what am I missing?

---What is the minimum distance between leaves that does away with any negative 3-leaf effects? If I have two walls built so that there's 8" between leaves, then another wall (leaf) 10' away, does that negatively effect my isolation?

I was never good at Sketchup, and now I'm also rusty and working on a 2018 version of the software. BUT, I'll try to get a basic model uploaded soon.

THANKS!

[gullfo]

since the slabs are earth damped, a flexible expansion seal works. as far as the cabling - if you run the conduit in the slabs, then added a flex-joint between them works well. otherwise, as noted about space above for mechanicals, consider running the conduit above and/or cable trays (you'll want access to clean and maintain the air handler and ERV unit, so a cable tray can ease the running of additional cabling later. a nice metal mesh one for RF protection is good).

10'6" cement floor to joist height minus 2x 5/8" + 1x 1/2" OSB will yield a nice 10'3" interior room height.

the exterior plan sounds good. the hardie board is nice and dense, if you were inclined to add more mass, i'd just simplify and just add the mass on the exterior overall.

for the frame, you only need about 1" gap between the frames. on a 2x6 exterior and 2x4 interior, you get 10" of air gap (filled with insulation of course), or with the foam on the 2x6, you get 4.5" air gap on the perimeter walls, and 8" on back to back interior walls. no need for hat channel on separate frames, if you do single frames, you'll want isolation clips + hat channel vs RC for better performance, although the dual frames is more betterer.

the 3-leaf effect is only when you have multiple air pockets in the walls / ceiling. your rooms don't count as a leaf...