Please Review & Comment on my Construction Plan

Greetings from the Long island, NY, USA area of the wide world of sound recording! I am a newbie! Thanks for your kind consideration! I am in the planning stage proposing to build a studio room in a free standing garage. The back ¾ of the structure will be utilized for the studio. It is a 13’ x 13’ space with a door leading to the front part of the garage which will be used for storage. The garage exterior is asbestos shingle covering wood siding with a layer of tar-paper in between. The interior of the building is exposed wood stud framework. There is a peaked interior with rafters and a double layer of standard shingle on the roof. There is an exposed concrete slab on the floor. There are no windows in the proposed room. The room’s purpose is as a MIDI/computer/controller recording studio with low-to-medium volume monitoring. Occasionally there may be one or two additional musicians in the space – rarely (or never) a drummer. My basic construction thoughts are as follows: Four (4) walls: - Insulate the exterior wall with standard insulation - Double rock with green glue – 5/8” + ½” standard drywall Floor: - Moisture barrier over concrete slab floor with industrial grade mat and carpet. Ceiling: - Floating joists - Plywood on top surface of ‘loft’ area above ceiling (to be utilized for storage) - Double rock and green glue as per wall construction. Notes: 1) I plan to rock and insulate the remainder of the garage with standard materials – no double-rock-green-glue technique. The additional space is approximately 8’ x 13’ with the same peaked ceiling. This front part of the garage will be used for storage. 2) I plan to install a steel garage door with insulation to assist in heat retainage and provide additional sound abatement. 3) The door to the studio space will be offset to the non-neighbor side of the building and will allow egress to the front portion of the garage where there is a side door – again to the non-neighbor side of the building and the roll-up garage overhead door. 4) Heat will be accomplished via free-standing electric heater. 5) There is existing mini-electric circuit breaker box fed via conduit from the house. I will have a licensed electrician rewire the garage outlets. It has been suggested that I should have separate circuits for electric and lighting/heating. 6) I have budgeted $4,000 USD and I have a friend whom I am compensating to do the grunt work. am i close to the mark? Over? Under? Additional areas of concern/questions: 1) Will a thru-wall AC unit compromise my soundproofing? I am considering installing a unit vented to the exterior of the building and mounted 3-4 “ above the finished floor. 2) How should I ventilate the room? How do I close off the A/C unit in winter (we are located in a northeastern state)? 3) What type of door is best? I am considering installing a slightly oversize door to the studio space. 4) What type of lighting should be used? High-hats, track lighting? 5) Is there anything I have left out of my plan? 6) I am attempting to strike a balance between cost and effectiveness. I love my music but I love my neighbors and family more! Thank you for any advice you can give me!

Johnny keyes wrote:

It is a 13’ x 13’ space

First thing you need to do is modify this square floor pattern. Also, sound is three dimensional, so we have to take into consideration the height of the space...what is it? Every dimension has modes associated with it, length, width, height does not matter since sound fills a room like a balloon. speed of sound(1130)/13 feet/one half wave length(2)=43Hz. Two things happen based on this number, one is that there is no resonant support for sound beyond this frequency. The other is that this axial mode being supported by two dimensions of the room will compound the issues at this and multiples of this frequency, e.g. 43Hz, 86Hz,129Hz,172Hz, etc. Actually there are three things, the third being since modes terminate in corners, this is the area that will get the biggest boost in low frequency and have you shaking your head every time you cut the bass, burn the CD, take it to the car and have to add more bass in the car because it seems to be missing from the CD :) This is the issue with a square room and small rooms in particular.

Johnny keyes wrote:

- Double rock with green glue – 5/8” + ½” standard drywall

Mass law predicts that for each doubling of mass you get a 4-5 dB gain in isolation. If you use 5/8" for one layer you should double that and add another layer of 5/8 sheetrock. As is you are losing the isolation ability by using a layer of less mass.

Johnny keyes wrote:

Floor: - Moisture barrier over concrete slab floor with industrial grade mat and carpet.

Does your slab sweat? If it does this may not be the place to make this room since the plastic is only going to be a barrier that the gaseous condensation will hit and follow the path of least resistance to get out, or lay and be a place for mold to feed off of.

Johnny keyes wrote:

Ceiling: - Floating joists

What does that mean? If you are not framing any interior wall assemblies then you are using the existing joists...how do you float a something that has no impact/placement point? So you are not so much interested in isolation for this build it seems, since you have not suggested an decoupling methods?