Detached 2 Car Garage Conversion

[srgdrum]

Hello Everyone! Great forum here. This is my first post so hopefully I can include all the pertinent information to get started.

First off I did buy Ron's book. Very informative and a great read. I will freely admit that much of it went directly over my head! Room modes and what not...

Ok. Here goes:

The space...

It's a detached 2 car garage. Single overhead garage door. Single 3068 swinging man door. No windows. Concrete block construction. Assuming it's 8". Dimensions are roughly 21' x 23' x 8' to a single layer drywall ceiling. We haven't moved into this space yet so I'm not sure of the joist sizes. The garage has an attic space so there's plywood of unknown thickness laid on the joists. The attic is tall enough for me to stand in the middle and I'm 6' 4". I feel like it's a decent space for the purpose.
Oh, the floor is concrete slab on grade.

My intent...

I'd like to have a combination recording/control room with the option to split the space into a more conventional layout in the future. Would be used for full rock band rehearsals/tracking. Think 110-120 db. I'm hoping for at least 50db TL. 60 would be better.

The bad...

I will need to keep some of the space for storage. At least 5' in depth and full width will be sacrificed. I will convert the overhead garage door to a pair of swinging carriage doors to remove the overheard track. This will require an interior isolation partition to be built behind this new door. I feel this will be the weakest link.
The nearest neighbor is approximately 20' from the west wall which is all block. The other neighbor is across an easement approx 35' away from the garage door opening side (south).
More bad stuff... The washer and dryer are in the garage for some reason and it seems that they will have to stay for now.
It is also NOT a conditioned space.

My questions....

1. I plan to build single leaf drywall partitions some distance behind the existing block. I'm not sure of the distance though. Roughly 4" is my thought. I could use 2 x 6 plates though if required. Wall will be constructed of 2 x 4's 24" on center. 2 layers 5/8" Firecode gyp board with proper sound caulk and backer rod. Staggered joints etc. Thinking of greenglue between the layers. I will insulate the cavities with sound batts/pink stuff.
Any thoughts on these walls? Is it required to finish tape/mud the first layer of drywall in multi-layer assemblies? Are we leaving a gap around the drywall sheets and sound caulking or butting hard to each other and fastening. Caulking at the perimeter only?

2. What's the best way to construct the wall behind the garage door? I was thinking this would be very similar to the other walls but shouldn't it have some sort of vapor barrier at the least? Should I use sheathing as a first layer? Would 3 layers of 5/8 gyp board be a better application here? Greenboard? Treated lumber? This wall confuses me most because of it's exposure and being behind the garage door. I will seal the new carriage door using commercial weather seals etc and perhaps add some insulation to the back of it but this assembly can't be too heavy. I'll build it from treated 2x materials and plywood. Strap style hinges.

3. The ceiling. I mentioned before the space has a flat drywall ceiling in place. I "assume" the joists are 2 x 4's. There is plywood laid over these to make an attic area currently. My thought is to remove all existing drywall and plywood. Insulate using pink stuff rolls stapled to the joists. Hang 2 layers of 5/8" Firecode on RC2... or would it be better to skip the resilient channel and use greenglue between the layers? Proper caulk, backer rod, staggered joints etc here too. Can I or should I reuse the existing plywood for a first layer with drywall over that? Thinking of saving money but I'm unsure of reusing any existing materials.

I plan on a mini-split HVAC system. Some of my concerns for the space is the HVAC. Because I live in South Florida (heat and humidity capital of the world) I worry about the conditioned space/non conditioned space interface. Should all these materials be purchased for damp spaces? Green board? Treated lumber? Vapor barriers? I'm not sure where to install the vapor barrier in this situation. It's the outside air that's warm and damp.

There's an existing 30 amp sub panel inside. It will have to be relocated. The existing man door isn't anything special. I guess I can hang another solid core wood door on the interior drywall partition with seals. I could add plenty of mass to this door. I work for a door / interior specialty company so most of this stuff wouldn't be a problem. It's just figuring out the proper building techniques.

Any tips hints or pointers you guys have would be greatly appreciated!

Thanks!

Scott

[srgdrum]

Any one? Bueller? 28 views and no notes?

Does any one have thoughts or input on this? Anything would be greatly appreciated.

[srgdrum]

57 views and not a peep? Have I posted this in the wrong section?

[srgdrum]

ttt!

Any help or critiques from anyone?

[Soundman2020]

Hi there Scott, welcome to the forum, and sorry for the delay in anyone getting back to you! Sometimes threads just "fall through the cracks", so to speak, and it seems that's what happened here. You've been more than patient, I must admit!

Anyway, comments on your project, in roughly the same order they came up in your original post:

The attic is tall enough for me to stand in the middle and I'm 6' 4". I feel like it's a decent space for the purpose.

Maybe I'm misunderstanding that, but are you planning to put part of your studio up in the attic space? Or are you just mentioning that to give a rough measure of the attic space, as part of the isolation plan?

he floor is concrete slab on grade.

Excellent!

No windows. Concrete block construction.

Also Excellent!

a single layer drywall ceiling

Not so excellent.

I'd like to have a combination recording/control room with the option to split the space into a more conventional layout in the future.

That might be an expensive proposition, unless you plan for it very carefully. Since isolation is normally done using the "room-within-the-room" concept, if you do that now then you would have to partly demolish a section o that "inner room" in order to split it half, then re-build the two parts of the dividing wall and re-build the ceiling too. If that's what you want to do, then you should build in the points now, where the room will be split later, and also build in the section to the ceiling where that will be split, so it can just be a matter of removing a small section of drywall on the side walls and ceiling, putting in the new framing, removing the pieces of the old framing, then putting on the new drywall.

Think 110-120 db. I'm hoping for at least 50db TL. 60 would be better.

Good. Those are realistic numbers and realistic goals.

I will need to keep some of the space for storage. At least 5' in depth and full width will be sacrificed. I will convert the overhead garage door to a pair of swinging carriage doors to remove the overheard track. This will require an interior isolation partition to be built behind this new door. I feel this will be the weakest link.

Right. If the rest of the outer-leaf walls are concrete block, then it will be really hard to maintain continuity of the surface density around the entire room, unless you build the new divider wall with concrete block too. However, since your goal is TL 50 to 60, that might not be necessary: it is possible to get that amount of isolation from drywall partitions, of done correctly.

And I beg to differ about that being your weakest link: Right now, your ceiling is your weakest link, by far.

1. I plan to build single leaf drywall partitions some distance behind the existing block. I'm not sure of the distance though. Roughly 4" is my thought.

An isolation wall is a tuned filter. At the frequency it is tuned to, it does not isolate at all, but above that frequency it isolates increasing well. So the trick is to tune it such that the resonant frequency is lower than the lowest one you need to isolate. You tune the wall by adjsuting the mass on each leaf, and the size of the air gap between the leaves. More mass= lower frequency. Bigger air gap= lower frequency. However, the "air gap" refers to the distance across the cavity between the two hard solid surfaces that define the leaves themselves, without considering the studs: they simply don't come into the picture when calculating the resonant frequency.

So, since the resonant frequency is the defining point, and since isolation rises at roughly 18 dB per octave from that point, what you need to define is what the lowest frequency is that you need to isolate, and how much isolation you need at that point.

I could use 2 x 6 plates though if required.

Not necessary. If the studs will be 2x4, then the plates can also be 2x4. The entire frame just needs to be set back from the block walls far enough to create the size of air gap that you need. That might be just a half inch away, or it might be several inches.

2 layers 5/8" Firecode gyp board with proper sound caulk and backer rod. Staggered joints etc. Thinking of greenglue between the layers. I will insulate the cavities with sound batts/pink stuff.

Perfect. That's the way to do it.

Any thoughts on these walls? Is it required to finish tape/mud the first layer of drywall in multi-layer assemblies?

Not a bad idea. It doesn't need to be pretty, of course! It will never be seen. As long as it ends up flush with the surface, that's fine.

2. What's the best way to construct the wall behind the garage door? I was thinking this would be very similar to the other walls but shouldn't it have some sort of vapor barrier at the least?

Yes, and very probably, but according to your local building code: that will tell you where to put the vapor barrier, if needed.

Should I use sheathing as a first layer?

I would use 5/8" or 3/4" plywood or OSB as the first layer, all around everywhere, on all your walls, and on your ceiling.

Would 3 layers of 5/8 gyp board be a better application here?

The number of layers depends on your isolation requirements, in terms of how much you need (how many decibels) and what the lowest frequency is that you need to isolate. They will determine how many layers.

3. The ceiling. I mentioned before the space has a flat drywall ceiling in place. I "assume" the joists are 2 x 4's.

Very probably they are larger than that, if they are spanning over 20 feet and also supporting the attic floor. I would suspect more like 2x8 or so.

My thought is to remove all existing drywall and plywood. Insulate using pink stuff rolls stapled to the joists. Hang 2 layers of 5/8" Firecode on RC2... or would it be better to skip the resilient channel and use greenglue between the layers?

Right, but here again I would make the first layer OSB or plywood, both for structural integrity and to give you an "all over" nailing surface, if you need it. And depending on how high you want your inner-leaf ceiling, you could even consider doing the leaf on top of the joists, instead of underneath it (provided that you have good access up there, and can seal that leaf to the outer-leaf walls: This is especially true, since you will have a 3-leaf ceiling here: the roof (outer leaf), that ceiling on the joists (middle-leaf) then the final inner-leaf ceiling, which will rest on the inner-leaf walls. So in order to get the inner-leaf ceiling as high as possible, you could consider doing it inside-out and tight up against those joists, with just a small gap between them, using the joists depth for the air gap and insulation.

Can I or should I reuse the existing plywood for a first layer with drywall over that?

If it is in god condition after you get it off (no holes, cracks, edge damage, etc), and is thick enough (at least 5/8"), then you could probably re-use that. Or keep it anyway, and re-use it in other non-critical areas where you'll need plywood later.

I plan on a mini-split HVAC system. Some of my concerns for the space is the HVAC.

OK; but a mini-split system is only a small part of your entire HVAC plan. It only covers the "AC" part of HVAC. Just as important is the Ventilation part. You need to get a constant supply of fresh air into the room (perhaps through a heat exchanger), and you need to exhaust the same amount of stale air out of the room (through the same heat exchanger, of course). And since you need a high level of isolation, you have to do that through large silencer boxes, to maintain the isolation, and ducts, and fans, and possible damper valves. It's an entire system, that needs to be calculated carefully.

Because I live in South Florida (heat and humidity capital of the world) I worry about the conditioned space/non conditioned space interface.

Then your calculations for the mini-split unit also have to be done very carefully, to take into account the very high latent heat load, as well as the sensible heat load. It would be very easy to under-dimension the system that you really need, based on the commonly quoted "square footage" of the room.

Should all these materials be purchased for damp spaces? Green board? Treated lumber? Vapor barriers? I'm not sure where to install the vapor barrier in this situation. It's the outside air that's warm and damp.

They should all be as specified by your local building code. Talk to a local contractor to find out how houses are built in your area, and what materials are used.

Any tips hints or pointers you guys have would be greatly appreciated!

There's a lot of information, tips and hints all over the forum: the problem is, it isn't indexed, and the search feature isn't fantastic, but it does help. I often find that just reading through the thread of someone's build can give you a wealth of stuff that you never knew, and also show you potential pitfalls that you can avoid, and things that you should do that you might not have thought of. Especially if the thread is about a place that is similar to yours.

Hope that helps to get you on the right track!

- Stuart -

[srgdrum]

Stuart!

Thanks very much for your detailed and thoughtful reply. I will try to answer your questions/provide further insight below.

The attic is tall enough for me to stand in the middle and I'm 6' 4". I feel like it's a decent space for the purpose.

Maybe I'm misunderstanding that, but are you planning to put part of your studio up in the attic space? Or are you just mentioning that to give a rough measure of the attic space, as part of the isolation plan?

I only stated this height for frame of reference. Trying to indicated that at at least some points the roof is quite far away from the ceiling structure.

I'd like to have a combination recording/control room with the option to split the space into a more conventional layout in the future.

That might be an expensive proposition, unless you plan for it very carefully. Since isolation is normally done using the "room-within-the-room" concept, if you do that now then you would have to partly demolish a section o that "inner room" in order to split it half, then re-build the two parts of the dividing wall and re-build the ceiling too. If that's what you want to do, then you should build in the points now, where the room will be split later, and also build in the section to the ceiling where that will be split, so it can just be a matter of removing a small section of drywall on the side walls and ceiling, putting in the new framing, removing the pieces of the old framing, then putting on the new drywall.

On second thought a combination room isn't such a bad thing. I typically just record myself anyway. I'm just looking for a decent room to record acoustic drums finally. Very tired of the ekit.

I will need to keep some of the space for storage. At least 5' in depth and full width will be sacrificed. I will convert the overhead garage door to a pair of swinging carriage doors to remove the overheard track. This will require an interior isolation partition to be built behind this new door. I feel this will be the weakest link.

Right. If the rest of the outer-leaf walls are concrete block, then it will be really hard to maintain continuity of the surface density around the entire room, unless you build the new divider wall with concrete block too. However, since your goal is TL 50 to 60, that might not be necessary: it is possible to get that amount of isolation from drywall partitions, of done correctly.

I can't use block for this partition.

And I beg to differ about that being your weakest link: Right now, your ceiling is your weakest link, by far.

I meant that when the space is finished the ceiling would be the weakest link since it would be a 3 leaf system counting the roofing.

1. I plan to build single leaf drywall partitions some distance behind the existing block. I'm not sure of the distance though. Roughly 4" is my thought.

An isolation wall is a tuned filter. At the frequency it is tuned to, it does not isolate at all, but above that frequency it isolates increasing well. So the trick is to tune it such that the resonant frequency is lower than the lowest one you need to isolate. You tune the wall by adjsuting the mass on each leaf, and the size of the air gap between the leaves. More mass= lower frequency. Bigger air gap= lower frequency. However, the "air gap" refers to the distance across the cavity between the two hard solid surfaces that define the leaves themselves, without considering the studs: they simply don't come into the picture when calculating the resonant frequency.

So, since the resonant frequency is the defining point, and since isolation rises at roughly 18 dB per octave from that point, what you need to define is what the lowest frequency is that you need to isolate, and how much isolation you need at that point.

I would think 40hz would be the lowest I'd be concerned with. I will search for a way to build partitions with this in mind.

I could use 2 x 6 plates though if required.

Not necessary. If the studs will be 2x4, then the plates can also be 2x4. The entire frame just needs to be set back from the block walls far enough to create the size of air gap that you need. That might be just a half inch away, or it might be several inches.

Thanks!

Any thoughts on these walls? Is it required to finish tape/mud the first layer of drywall in multi-layer assemblies?

Not a bad idea. It doesn't need to be pretty, of course! It will never be seen. As long as it ends up flush with the surface, that's fine.

Thanks! Any mudding/taping I do is not going to be pretty.

2. What's the best way to construct the wall behind the garage door? I was thinking this would be very similar to the other walls but shouldn't it have some sort of vapor barrier at the least?

Yes, and very probably, but according to your local building code: that will tell you where to put the vapor barrier, if needed.

I will look into this. I wanted to submit drawings just once for the permits. The more detailed I can be the better.

Should I use sheathing as a first layer?

I would use 5/8" or 3/4" plywood or OSB as the first layer, all around everywhere, on all your walls, and on your ceiling.

OK. I will sub the first layer of 5/8" gyp for OSB.

3. The ceiling. I mentioned before the space has a flat drywall ceiling in place. I "assume" the joists are 2 x 4's.

Very probably they are larger than that, if they are spanning over 20 feet and also supporting the attic floor. I would suspect more like 2x8 or so.

Will confirm.

My thought is to remove all existing drywall and plywood. Insulate using pink stuff rolls stapled to the joists. Hang 2 layers of 5/8" Firecode on RC2... or would it be better to skip the resilient channel and use greenglue between the layers?

Right, but here again I would make the first layer OSB or plywood, both for structural integrity and to give you an "all over" nailing surface, if you need it. And depending on how high you want your inner-leaf ceiling, you could even consider doing the leaf on top of the joists, instead of underneath it (provided that you have good access up there, and can seal that leaf to the outer-leaf walls: This is especially true, since you will have a 3-leaf ceiling here: the roof (outer leaf), that ceiling on the joists (middle-leaf) then the final inner-leaf ceiling, which will rest on the inner-leaf walls. So in order to get the inner-leaf ceiling as high as possible, you could consider doing it inside-out and tight up against those joists, with just a small gap between them, using the joists depth for the air gap and insulation.

This inside out construction would be fiendishly difficult towards the eaves. I also really don't have a height issue. I can stand the loss of 1-3/4" - 2". Will def sub OSB for the first layer. Excellentt point for an all over fastening surface. Of course being careful not to short out the RC. I do have concerns of this much weight on the RC2 but the manufacturer says its ok.

Can I or should I reuse the existing plywood for a first layer with drywall over that?

If it is in god condition after you get it off (no holes, cracks, edge damage, etc), and is thick enough (at least 5/8"), then you could probably re-use that. Or keep it anyway, and re-use it in other non-critical areas where you'll need plywood later.

Ok

I plan on a mini-split HVAC system. Some of my concerns for the space is the HVAC.

OK; but a mini-split system is only a small part of your entire HVAC plan. It only covers the "AC" part of HVAC. Just as important is the Ventilation part. You need to get a constant supply of fresh air into the room (perhaps through a heat exchanger), and you need to exhaust the same amount of stale air out of the room (through the same heat exchanger, of course). And since you need a high level of isolation, you have to do that through large silencer boxes, to maintain the isolation, and ducts, and fans, and possible damper valves. It's an entire system, that needs to be calculated carefully.

I have been looking at peoples plans for the silencer boxes.

Because I live in South Florida (heat and humidity capital of the world) I worry about the conditioned space/non conditioned space interface.

Then your calculations for the mini-split unit also have to be done very carefully, to take into account the very high latent heat load, as well as the sensible heat load. It would be very easy to under-dimension the system that you really need, based on the commonly quoted "square footage" of the room.

I planned on bumping up the units BTU's to better accomodate a higher heat/humidity load. Careful calculation will be used here!

Should all these materials be purchased for damp spaces? Green board? Treated lumber? Vapor barriers? I'm not sure where to install the vapor barrier in this situation. It's the outside air that's warm and damp.

They should all be as specified by your local building code. Talk to a local contractor to find out how houses are built in your area, and what materials are used.

That's pretty easy. I've got those sorts of unsavory characters right down the hall at work!

Any tips hints or pointers you guys have would be greatly appreciated!

There's a lot of information, tips and hints all over the forum: the problem is, it isn't indexed, and the search feature isn't fantastic, but it does help. I often find that just reading through the thread of someone's build can give you a wealth of stuff that you never knew, and also show you potential pitfalls that you can avoid, and things that you should do that you might not have thought of. Especially if the thread is about a place that is similar to yours.

I'm def reading!

Hope that helps to get you on the right track!

- Stuart -[/quote]

Thanks again for your help!

[Soundman2020]

I only stated this height for frame of reference. Trying to indicated that at at least some points the roof is quite far away from the ceiling structure.

OK, that's what I was hoping you would say!

I can't use block for this partition.

No problem: you can still do it with drywall.

when the space is finished the ceiling would be the weakest link since it would be a 3 leaf system counting the roofing.

Right. Sometimes you have to do 3-leaf, and when that happens the best solution is to have more mass on the middle leaf, and large air gaps, to compensate for the poorer low-frequency isolation. So you should be fine in your case.

This inside out construction would be fiendishly difficult towards the eaves.

Yup. But you might be able to do most of it from above, and just around the edges from below. Or just keep your life simple, and do it all from below.

I planned on bumping up the units BTU's to better accomodate a higher heat/humidity load. Careful calculation will be used here!

Right! You also have to be careful not to over-size the cooling capacity. It's almost as bad as under-sizing. If the unit is too big, the duty cycle will be very short, so it will not remove enough humidity in each brief "on" cycle, and the temperature and humidity will also swing up and down all the time, rather than being held more or less constant. So it needs to be sized right.

- Stuart -