Yet another double garage to studio conversion

Hi guys, This forum is excellent I have been trawling it for months and I am learning so much more every time. So thank you to everyone that contributes their time to this forum. It is very much appreciated. I have done my best to address all the forum rules please let me know if I can provide any more details. I know there is a lot I don't know and please forgive me for any obvious or stupid questions. My partner has graciously allowed me free reign over the double garage of our newly purchased home in NSW, Australia and I intend to turn it into my studio to use professionally and for my own recording and rehearsal. The expected noise level is going to be quite low most of the time for mixing and song writing, though I do intend to do drum and bass tracking occasionally and hopefully use it for a rehearsal space, so I expect the noise to get anywhere near 110dB at times and I need external noise not to disturb neighbours. The closest house to the garage is around 6m separated by a driveway and fence. The garage is a separate structure on a single concrete slab constructed of a wooden frame with a weatherboard exterior and a corrugated steel roof. I would like to have a control room and live room to have the flexibility of tracking drums isolated from the monitors and to able to multitrack two isolated sources. I have included my sketchup plans for what I have in mind so far (forgive my limited sketchup skill, first timer). . I tried to account for standing waves, making my opposite walls at least 12 degrees offset in both rooms. I am still a little uncertain about the ceiling. It is 2390mm from the floor to the existing ceiling joist of the garage. I wanted to angle the studio ceiling but I don't think it is possible with the limited height. It would be great to get this within $5000AUD, but reading around this forum I have a feeling I may have to stretch further than this. I am still in very early stages of planning and still have a lot of learning and reading to do! I would really appreciate anyones input on my design as I am sure I am missing plenty of things. 1. Is this an effective layout in terms of acoustics and use of space? 2. Is $5000 a realistic budget for this project? 3. I can't have my ceiling at 12 degrees due to space. Is it going to be beneficial to have my ceiling at a smaller angle or should I just not bother and deal with the issues related to the parallel roof to floor with acoustic treatment? 4. I am planning on using resilient channel to mount the drywall. Will it be beneficial to use it on both external and internal drywall layers of my inner structure or do I only need to use it on the inner layer? 5. My one other concern, and this is purely lack of construction knowledge, is if I am putting drywall on both sides of my inner structure, do I need to leave enough space between the existing structure of the garage and my inner structure to allow for a person to get in and install drywall? I left 400mm on the side with no access (behind the front wall of my control room) just as a guess. =S Thank you in advance for your advice. Jake

Hi guys, Just an update to save anyone wasting time answering questions and also to help any newcomers. I managed to answer these myself as I read more and more of these forums and talk to more people. I have pushed the front walls (opposite the doors) closer to the existing structure, having gotten confirmation that I can put the outer layers of drywall on the frame before standing it up. I have bumped the budget to $10,000 AUD as I think that is a little more realistic if I want to do this properly. I am still yet to do actual estimated costs as I am waiting for CAD drawings and material estimates from a helpful friend! I have since learned that I only need resilient channel on the inner layer. From what I can read decoupling the outer layer would be a waste of money if I have already decoupled on the inner layer. I am actually probably going to go with resilient mounts for furring channel as it is available from my local hardware store. I am feeling more and more confident thanks to you guys. I am still open to suggestions on layout and ceiling (though I think I will just have to make do in that area). I realised I didn't actually include the dimensions of the garage as requested by the forum rules, for some reason I thought the sketch up would cover that (idiot). The floor space I have to work with is 7.65m x 6m. It is slightly less though as the garage doors take off 430mm when open. As I said the height I have to work with is 2.39m from floor surface to the bottom of the existing joists. I am struggling to find much information about anchoring my frame to the existing concrete slab. I would really appreciate any recommendations in this area. Will I be losing much isolation if I use the standard construction procedure of anchoring the frame, which I assume is bolts of some kind? Thank you again! I will update with more information and the new CAD drawings as they come through.

Hi Jake, and Welcome! :)

so I expect the noise to get anywhere near 110dB at times

Drums can actually go quite a bit louder than that: Count on 115, perhaps even heading for 120.

The garage is a separate structure on a single concrete slab

That's good news!

of a wooden frame with a weatherboard exterior and a corrugated steel roof.

That's not so good news. That roof will need "beefing up" with mass to create your outer leaf, or alternatively you'll need to go with a 3-leaf system, blocking off the attic space entirely.

I tried to account for standing waves, making my opposite walls at least 12 degrees offset in both rooms.

That won't do much for room modes (standing waves). It will help for flutter echo, but not modes. That's a common myth, actually: Angling (or "splaying") your walls does not eliminate room modes: it just moves them to a different frequency and location, and makes them harder to calculate.

I wanted to angle the studio ceiling but I don't think it is possible with the limited height.

Right. Just keep it flat, then hang a hard-backed, angled cloud.

is if I am putting drywall on both sides of my inner structure,

:shock: :cop: :roll: You don't do that! :!: You only put drywall on ONE side of your inner-leaf. Never on both sides.

, having gotten confirmation that I can put the outer layers of drywall on the frame before standing it up.

Once again, you do NOT need to put drywall on both sides of your inner-leaf framing. It only goes on ONE side. That can be either the side facing the air gap, or it can be the side facing the room. But only one, not both.

I have since learned that I only need resilient channel on the inner layer. From what I can read decoupling the outer layer would be a waste of money if I have already decoupled on the inner layer.

You arelay HAVE the outer leaf! It is the existing garage. That is already there. It might need beefing up, but you don't need another one. All you need now is your INNER leaf, which is just stud framing with drywall on only ONE side of the studs.

I am actually probably going to go with resilient mounts for furring channel as it is available from my local hardware store.

... and increase your costs considerably! :) You do not need RSIC clips, or furring channel, or RC, or anything similar. As you already mentioned you are going to put up your inner leaf as studs with drywall on them: that's all the decoupling you need. As long as you make sure that your inner-leaf walls do not touch the existing garage structure at any point, then you are fine.

It is slightly less though as the garage doors take off 430mm when open.

Does it need to open, ever again, after your studio is built? Most people just fis the garage doors in place permanently, then remove the mechanism and build a wall just a few cm away from the now-fixed door, to complete the outer leaf. Then build the inner-leaf.

I am still open to suggestions on layout and ceiling

Your ceiling should be done the same as the walls: outer leaf (roof), and inner-leaf (which rests ONLY on the inner-leaf walls, not touching the outer leaf anywhere).

I am struggling to find much information about anchoring my frame to the existing concrete slab. I would really appreciate any recommendations in this area.

Just use anchor bolts. After the walls are up, drill down through the sole plate and into the concrete, then drop in an expanding anchor bolt and tighten it up. Do that every few feet, as required by your local building code.

Will I be losing much isolation if I use the standard construction procedure of anchoring the frame,

You still need to create the seal: Before you put the sole plate in position, run three beads of caulk along it, or along the floor where it will be. One bead goes down the center-line of the sole plate, then the other two go about 2cm each side of that, so you have three full-length seals. Then after it is bolted down, caulk along the edges to create two more seals. Then caulk under each layer of drywall as you put it up, for additional seals. - Stuart -

Hi Stuart, Thank you so much for taking the time to read and reply. I am so grateful for this resource!

Drums can actually go quite a bit louder than that: Count on 115, perhaps even heading for 120

Good point! I will now account for 120 as a worst case scenario. I would like to aim for 70dB I hope that is realistic with my budget. 60dB would be excellent.

That won't do much for room modes (standing waves). It will help for flutter echo, but not modes. That's a common myth, actually: Angling (or "splaying") your walls does not eliminate room modes: it just moves them to a different frequency and location, and makes them harder to calculate.

Thank you for pulling me up on this one! I completely misunderstood the SAE information and anywhere else I had read about the 12 degrees :oops: . In light of this, I am now aiming to build two rectangle rooms (using mode calculators to find the best ratios I can) then use acoustic treatment to deal with reflection control.

You still need to create the seal: Before you put the sole plate in position, run three beads of caulk along it, or along the floor where it will be. One bead goes down the center-line of the sole plate, then the other two go about 2cm each side of that, so you have three full-length seals. Then after it is bolted down, caulk along the edges to create two more seals. Then caulk under each layer of drywall as you put it up, for additional seals

Thank you for the advice, I am feeling confident with this area now. In regards to the structure I had planned. I think I was trying to propose a 3-leaf system. That is, the first leaf being the decoupled drywall on resilient channel. The second leaf then being the drywall attached directly to the framing on the outside. The third leaf being the existing shed structure. I chose this as I thought beefing up the shed structure was going to be too costly having to deal with three garage doors, a window and a corrugated roof. Is what I am proposing actually a 3-leaf system or is the second leaf (outer drywall) useless regardless of resilient channel usage on the inner layer? Do you think it would be more cost effective to go with a 2-leaf structure and spend the extra cash on beefing up the outer leaf (existing garage), perhaps sealing garage doors and removing mechanisms as you say and potentially sealing the attic? Is 120dB to 70dB a realistic goal here? Much like most other small studios on this forum, for the most part I will be making very little noise. Just mixing at around 70dB and songwriting. I won't do drum tracking often and it will be in the day so isolation doesn't have to be too over the top. I know I have said it already but your insight is very much appreciated. Jake

Hi guys, I am making progress slowly, and I really appreciate all the help so far. At this stage I can't see any effective ways of beefing up the outer leaf (the existing shed structure of weatherboard and corrugated steel roof) that would be within my budget. Making this structure airtight would involve sealing the gap between the roof and walls and sealing off the 3 garage doors and replacing the window. I was hoping to at least keep one garage door for easy load-in access from the driveway. I think I will be able to achieve the isolation I need with a well built inner leaf. At the moment I am getting about 30dB reduction at 6 foot from existing structure with a sound source of 100dB. I have attached a PDF to show how the rooms will be fitting within the garage. I have redesigned the layout of the rooms to be rectangles and used Bob Gold's Room Modes calculator to make sure the dimensions don't create any unwanted modes. I plan to be doing a lot of treatment in the rooms to deal with reflections but that will be another topic altogether once I have this built! Unfortunately I don't have the option of inside out walls, as I will need the exposed joists on the ceiling to be on the outside to fit between the existing joists of the shed, allowing me a lot more ceiling room. I am now looking into HVAC. No surprise, it is just as confronting as everyone says. I am going to head out to some local air con places and see what they recommend. From my research, it seems as though I am possibly looking for two quiet mini-splits that have the ability to supply fresh air. Am I missing anything? The inner leaf will be rockwool(or equivalent) two layers of drywall, different thickness, and green glue(or equivalent). I understand this is quite a vague guide to materials at the moment but would it be possible to get an estimate on what sort of isolation you think I will be able to achieve without beefing up the outer layer? Are there any other things in particular I need to keep in mind in regards to HVAC when I am getting quotes for air con units? Thanks again!

I think I will be able to achieve the isolation I need with a well built inner leaf.

If you don't seal the outer leaf, and put enough mass on it, then the inner leaf will basically act like a single leaf, subject to mass law, and not so much like a 2-leaf MSM system. So you'd probably get about 6 dB to 10 dB of additional isolation, beyond what you have now. Leaving the garage door in place and operable also severely limits the maximum height for the room.

At the moment I am getting about 30dB reduction at 6 foot from existing structure with a sound source of 100dB.

The correct place to measure is at three feet from the wall, so likely you are getting around about 25 dB reduction. Adding the inner leaf will increase that to something like 30 to 35 dB of isolation. So your 100 dB level inside will be around 65 to 70 dB outside.

I plan to be doing a lot of treatment in the rooms to deal with reflections but that will be another topic altogether once I have this built!

It is better to design the treatment at the same time as you design the rest of the room. Otherwise you normally end up with conflicts that cannot be resolved, except be taking things apart and re-building them. Issues such as needing to move doors or windows so that the treatment can go where it is needed, for example, or HVAC ducts, registers, or silencer boxes being in places where treatment needs to go, or where HVAC airflow will be interrupted by treatment. The entire design should be absolutely complete in all aspects before you start building anything. if not, you are pretty much guaranteed to run into problems that will prevent you from doing things optimally.

Unfortunately I don't have the option of inside out walls, as I will need the exposed joists on the ceiling

I don't see the connection there at all! Why would ceiling joists interfere with whether or not you can have inside out walls? There's no relationship that I can see.

as I will need the exposed joists on the ceiling to be on the outside to fit between the existing joists of the shed, allowing me a lot more ceiling room.

If you do it that way, you will be LOSING height in your final finished ceiling surface! :wink: Think it through... :) with an inside out ceiling, the drywall goes just below the outer-leaf joists, then come the inner-leaf joists which have the final treatment in between them, so the bottom surface of the inner-leaf joists IS the lowest point in the room. If you do it conventionally, then your ceiling drywall might be a little higher than what the bottom surface of the joists would have been for the inside-out ceiling, but then you still need to hang your ceiling treatment below that, so the final surface is a lot lower... Try out both alternatives in your SketchUp model, so you can see the difference....

I am going to head out to some local air con places and see what they recommend.

Careful with that approach! Very, very few air conditioning stores have even the vaguest idea of what a recording studio needs, or how it is built, or how to install a system for a studio. It is far better to work through the math yourself, then go to the store and tell them what you need.

it seems as though I am possibly looking for two quiet mini-splits that have the ability to supply fresh air.

Those are really expensive, and likely don't supply enough air anyway. A studio needs about 8 air changes per hour, so figure out how much that is for your studio, check the specs for the unit you are thinking of buying, and see how close they are....

Am I missing anything?

yep.... :) While a mini-split with a fresh air supply might be able to bring some air into the room, where does it go after that? :shock: You also need ducting to exhaust the stale air from the room. In a normal house installation for those things, that isn't a problem since houses are very "leaky", so the small amount of exhaust air will find its own path out: But studios are sealed air-tight. there is path out. So you have to create one, with ducts, silencer boxes and fans. And since you need to go to all that trouble anyway, you might just as well buy a cheaper mini-split without that feature, and do the ducting properly... :)

two layers of drywall, different thickness,

That's a myth: you do not need different thicknesses of drywall. Yes, there is a slight advantage in impedance mismatch from doing that, but you would more than make up for that from the increased mass and reduced flexibility by just making both of the layers as thick as the thicker one. So 2 layers of 5/8" will give you better isolation than one layer of 5/8 plus one layer of 1/2.

and green glue(or equivalent).

There is no "equivalent" :) :!: 8) Or at least, there are others that claim to be equivalent, but their supporting documentation is rather wanting... Always be aware of any manufacturer that makes wonderful claims for their acoustic products, but then does not back it up by supplying the results of testing conducting in an independent, reputable acoustical laboratory... :)

I understand this is quite a vague guide to materials at the moment but would it be possible to get an estimate on what sort of isolation you think I will be able to achieve without beefing up the outer layer?

At a rough guess, I would estimate something in the region of 35 dB to 40 dB of isolation, with luck. - Stuart -