Building a 2nd structure inside my garage

[Bob_McPhee]

I'm a teacher and musician who wants to build a soundproof band practice space inside my detached cinder block garage:

Ideally, I would build a SECOND cinderblock room WITHIN this garage; any sound escaping the inner cinderblock room would be contained by the actual garage and my neighbors should be happy.

I'm planning on making the inner room 15'x12'. With ~8ft ceilings, that gives me a rough estimate of 432 sq ft of cinderblocks. An 8"x8"x16" open cell cinderblock weighs 36-40lbs according to google, so I'll say 432 cinderblocks times 38lbs = 16,416 lbs !!!

And that's not counting the grout filling the cells, cement ceiling, and double doors!

Unfortunately I don't know how thick the concrete slab floor of my garage is, or the type of concrete. I don't know if they used rebar reinforcements. I dug at one corner of the garage to reveal 2.5 deep footings, but then realized the cinderblock walls of the garage are resting on those footings and that the slab is 'floating' on hopefully compacted earth.

Now the previous owner used to house 2 hot rods and some other heavy equipment in there for years, no cracks.

My brother in law, who is in construction, is helping me with this project and he thinks it could work. I have my doubts. He says he's stored his 2-ton truck, a lift, skid loader, and over 10,000lbs of 5/8 drywall in his old garage with a 4 inch slab for years with out problems.

Assuming I have a 4 inch slab with no rebar, and probably 3500 psi concrete, can that hold a 12'x15' cinderblock structure that weighs 17,000-20,000lbs? I'm thinking no but my brother in law disagrees.....

Expert advice is appreciated!!!

 

[JamesW84]

Not sure, but I think I'd just frame it with 2x6's or 2 rows of 2x4's and put 6 more inches of fiberglass insulation in the walls. Research the better sound blocker: drywall vs plywood, etc

 

[JRC3]

Not sure, but I think I'd just frame it with 2x6's or 2 rows of 2x4's and put 6 more inches of fiberglass insulation in the walls. Research the better sound blocker: drywall vs plywood, etc

That's what I was thinking too. Sure would be easier to modify on down he road, run wire, hang things from, etc. I also think it'd be more sound deadening.

And of course, as usual, not knowing the location hinders advice. For one reason, AC, heat or humidity could be a factor.

 

[Stuart in MN]

Here's the picture, you have to change the 'https' to 'http' to get Imgur pictures to show up here.

 

[Bob_McPhee]

Not sure, but I think I'd just frame it with 2x6's or 2 rows of 2x4's and put 6 more inches of fiberglass insulation in the walls. Research the better sound blocker: drywall vs plywood, etc

That's what I was thinking too. Sure would be easier to modify on down he road, run wire, hang things from, etc. I also think it'd be more sound deadening.

And of course, as usual, not knowing the location hinders advice. For one reason, AC, heat or humidity could be a factor.

Yes that was also my original thought! But I soon learned soundproofing low end bass frequencies from a loud bass amp and full drumkit are much much more difficult; decades of soundproofing research tells you that a room within a room using materials with lots of mass/density (cement cinderblock) will tame down those rumbling sounds much better than standard framing + drywall. Insulation, oddly enough, does very little for soundproofing (don't ever buy the expensive acoustic insulation for studios, it's a ripoff).

Ventilation is a WHOLE other thing but I think I got that covered.

EDIT: I'm in a dry climate near Arizona.

My next best option, if my garage slab can't support a cinderblock structure, is a double 5/8 drywall, double wall, 12'x15' room. Drywall itself has a fair amount of mass (density) to it, just not as much as cinderblock filled with concrete.

 

[SALIV8]

I think pros like to de couple the drywall from the wall using hat channel or similar. So maybe double drywall then hatchannel then another layer of drywall.

 

[Old Man Roger]

Just for the sake of resale, I would want it to be a temporary structure.

Really curious about your plans for ventilation. My completely uneducated guess would be an s shaped insulated forced induction?

Would love to know the final cost too, if that's not too personal.

 

[Ironcrow]

Decouple with a stick frame structure inside the garage. Sheet with Quietrock 545. This problem has been solved. No need to reinvent the wheel.

https://www.quietrock.com/products/quietrock-545

Study up on schemes to seal up holes, decouple parts of assembly, add sound deadening between building envelop layers...

 

[Bob_McPhee]

I think pros like to de couple the drywall from the wall using hat channel or similar. So maybe double drywall then hatchannel then another layer of drywall.

Yes decoupling is a huge part of soundproofing. Hanging drywall on a hat channel serves this purpose well.

But I'm fortunate to know the head recording engineer at the local University who not only oversaw the recording studio being built but he's also built 2 of his own studios: 1 in his basement and 1 in a garage. He said the best soundproofing performance is in this order:

1. cinder block room WITHIN the cinderblock garage
2. double 5/8 drywall on a double wall room WITHIN the cinderblock garage
3. framing the entire garage + double drywall on a hat channel

Hat channels only provide SOME decoupling. They work well in commercial condos etc. where you're trying to isolate human voices, tv's, radios etc. For full band/bass amp/low frequency isolation the room within a room gives you a higher level of decoupling.

The home theater guys at the AVS forum taught me lot; they're watching action flicks on huge double subwoofers in their basement theater without waking the wife upstairs

 

[rsanter]

Build a 6” wall using 2x4 stagger stud construction.
Rock wool insulation and quiet rock covering.

Foam and quiet rock on the exsisting walls

 

[Bob_McPhee]

Just for the sake of resale, I would want it to be a temporary structure.

Really curious about your plans for ventilation. My completely uneducated guess would be an s shaped insulated forced induction?

Would love to know the final cost too, if that's not too personal.

Everyone who I trust has told me to always consider resale. This is the wife and I's first home and of course we're hoping the last, but you're right.

Ventilation will be 2 holes on opposite walls connected to baffle boxes with inline fans. This is a crude version but the more times sound has to change direction the more it's deadened. I will also line the box with sound absorbing materials.

EDIT:

I'm planning on keeping it under $5000 (I know, I know haha). Fortunately my brother in law can get me 5/8 drywall for $7 a sheet! Might go with drywall for that reason alone.

Decouple with a stick frame structure inside the garage. Sheet with Quietrock 545. This problem has been solved. No need to reinvent the wheel.

*quiet rock link*

Study up on schemes to seal up holes, decouple parts of assembly, add sound deadening between building envelop layers...

You're spot on. The recording engineer mentioned quietrock but it's EXPENSIVE. I told him my brother can get 5/8 drywall for $7 a sheet and he said to double it with green glue in between. I'll calculate a budget for quietrock though and consider it.

 

[Bob_McPhee]

Build a 6” wall using 2x4 stagger stud construction.
Rock wool insulation and quiet rock covering.

Foam and quiet rock on the exsisting walls

I also researched staggered stud and studies show it can outperform hat channels. It's also easier and cheaper. However double stud walls (2 seperate walls an inch apart with R13) outperform both. It takes up more room, but I have room to spare.

You guys know your stuff, cool forum.

 

[Bigbandguy]

If you are just rehearsing could you not tone down the bass somewhat? Bass tones really carry and of course any subwoofer type sound carries even more, but if you are practicing ensemble, singers, blend , arrangements, etc is it necessary to have the bass at earth shattering levels? Admittedly I know more about rehearsing horns than rhythm instruments, but it seems to me that a little compromise on sound pressure levels at the very low end could go a long way toward lessening the need for the double wall. I guess the question is how much do you want the bass player's ego to cost you?

 

[Old Man Roger]

Bob, that ventilation box is very close to what I was thinking. Ventilation in a soundproof room always boggled my mind..lol
They go through so much trouble sealing every little crack, then you see giant vents

The one guy I know that works for Audio Advisors, says the quick and dirty secret is air gaps between layers. Obviously density is good, but he says layers and air gap are more important than anything. The more layers the better.

He does whole home sound systems and theaters for the people who live on the island of Palm Beach. The uber-rich.

 

[ard]

You gonna have a cinderblock CEILING too????

Your overall soundproofing is only as good as your weakest link. Focusing on walls- two walls of block, blah blah -and blithely ignoring the ceilings is a big fail. IMO

 

[Glory]

Tested STC assemblies can be found all over manufacturers websites. What is the performance spec your trying to achieve with your cmu assembly?

I don’t understand... are you trying to backyard engineer it and just bouncing your ideas off GJ folks? These problems have been solved already, what is it that you are trying to achieve other than being unconventional?

 

[JRC3]

I don’t understand... are you trying to backyard engineer it and just bouncing your ideas off GJ folks?

I think he was asking because f the weight on the slab.

I'm planning on making the inner room 15'x12'. With ~8ft ceilings, that gives me a rough estimate of 432 sq ft of cinderblocks. An 8"x8"x16" open cell cinderblock weighs 36-40lbs according to google, so I'll say 432 cinderblocks times 38lbs = 16,416 lbs !!!

 

[mike93lx]

100% a wood structure, with rockwool insulation and either dual layer drywall or decoupled. Add in some surface mount sound insulation inside the room and you'll be in great shape.

No chance I would build that room out of CMU

 

[dcg9381]

Are you talking about doubling up the CMU on the exterior side? If not, your issue with bass transmission seems to be to the adjacent properties, you'd still have the same bass propagation in at least one direction.

I'm with others - there are better ways to insulate for sound than CMU.

In terms of can your foundation hold it - it's an evenly spread 14k load across 14-18'. No one can tell you for sure because we don't know the design of your foundation or the soil under it, but many vehicles have more significant load points (RVs, some boats, etc).

 

[Kevin54]

We had soundproof rooms at work that was built with metal studs, insulated with rockwool, drywalled, then covered with soundproofing foam. The rooms for our vibration labs were loud inside, and no noise outside.

 

[Barnabas]

Preventing sound from going through a wall and preventing sounds from bouncing off walls are two different things.

Mass keeps sound from going through a wall. That means brick, drywall, MDF. Multiple layers separated by an air gap is better.

The "egg shell" foam panels are not designed to keep sound from going through it, it is designed to keep sound from bouncing off the walls.

You are getting good advice about sound proofing your walls. I think multiple layers of drywall will work better than concrete brick. Regular brick would be better. If you fill the holes on the concrete brick, it will work much better.

Consider non-parallel walls to keep down the standing waves within the room. You do not want the sound to bounce back and forth between two parallel walls. Those foam panels are good on the wall. One-by-one strips of wood or plastic mounted on the walls will also disrupt the sound waves from bouncing directly off the walls. Dispersing the waves with wood strips and foam will help to disapate them. This means the sound will not build up to deafening levels.

Carpet will be good on the floor. The deeper the better for sound purposes, but short enough to make it usable.

Best if the ceiling is not level, parallel to the floor. Corrugated metal or plastic on the ceiling and/or walls will help disperse the standing waves.

Research bass traps. Basically a large trash an in the corner of the room stuffed with insulation. This helps to keep the bass levels from accelerating out of control.

 

[Bob_McPhee]

If you are just rehearsing could you not tone down the bass somewhat? Bass tones really carry and of course any subwoofer type sound carries even more, but if you are practicing ensemble, singers, blend , arrangements, etc is it necessary to have the bass at earth shattering levels? Admittedly I know more about rehearsing horns than rhythm instruments, but it seems to me that a little compromise on sound pressure levels at the very low end could go a long way toward lessening the need for the double wall. I guess the question is how much do you want the bass player's ego to cost you?

You're forgetting the drummer haha. We try to practice same as we play, some are loud, some are quiet.

Bob, that ventilation box is very close to what I was thinking. Ventilation in a soundproof room always boggled my mind..lol
They go through so much trouble sealing every little crack, then you see giant vents

The one guy I know that works for Audio Advisors, says the quick and dirty secret is air gaps between layers. Obviously density is good, but he says layers and air gap are more important than anything. The more layers the better.

He does whole home sound systems and theaters for the people who live on the island of Palm Beach. The uber-rich.

I've read a lot about air gaps. I believe that's called a 2 leaf system. The air gap (w R13 insulation loosely packed) really helps break down low frequencies. You're supposed to avoid a 3 leaf system (2 air gaps or something like that) because they'll actually resonate loudly.

 

[Bob_McPhee]

You gonna have a cinderblock CEILING too????

Your overall soundproofing is only as good as your weakest link. Focusing on walls- two walls of block, blah blah -and blithely ignoring the ceilings is a big fail. IMO

Yep got the ceiling covered. Probably vertical 2x4 joists 10" apart. Either a layer of plywood or metal decking with around 2" of concrete poured. Got the idea from this guy:

Tested STC assemblies can be found all over manufacturers websites. What is the performance spec your trying to achieve with your cmu assembly?

I don’t understand... are you trying to backyard engineer it and just bouncing your ideas off GJ folks? These problems have been solved already, what is it that you are trying to achieve other than being unconventional?

Yea like JRC said, just looking for some expertise/experience to confirm my doubts about the the weight of a cinderblock structure on my garage slab. We got a good soundproofing discussion going, it's been one of my passions for the last couple years. There's always people out there who know more than you, that's why these forums are great!

 

[Bob_McPhee]

100% a wood structure, with rockwool insulation and either dual layer drywall or decoupled. Add in some surface mount sound insulation inside the room and you'll be in great shape.

No chance I would build that room out of CMU

Why risk it? Double wall drywall will be time consuming but not terribly expensive and my dad can help.

Are you talking about doubling up the CMU on the exterior side? If not, your issue with bass transmission seems to be to the adjacent properties, you'd still have the same bass propagation in at least one direction.

I'm with others - there are better ways to insulate for sound than CMU.

In terms of can your foundation hold it - it's an evenly spread 14k load across 14-18'. No one can tell you for sure because we don't know the design of your foundation or the soil under it, but many vehicles have more significant load points (RVs, some boats, etc).

That's my brother in law's argument, and it is based on experience. Not knowing the true design of my slab is where I'm thinking it's not worth the risk. Concrete starts cracking, whole thing could be ruined.

We had soundproof rooms at work that was built with metal studs, insulated with rockwool, drywalled, then covered with soundproofing foam. The rooms for our vibration labs were loud inside, and no noise outside.

Metals studs are better than wood. Expensive so I might try them in a future project but keep this one simple (as possible).

 

[Bob_McPhee]

Preventing sound from going through a wall and preventing sounds from bouncing off walls are two different things.

Mass keeps sound from going through a wall. That means brick, drywall, MDF. Multiple layers separated by an air gap is better.

The "egg shell" foam panels are not designed to keep sound from going through it, it is designed to keep sound from bouncing off the walls.

You are getting good advice about sound proofing your walls. I think multiple layers of drywall will work better than concrete brick. Regular brick would be better. If you fill the holes on the concrete brick, it will work much better.

Consider non-parallel walls to keep down the standing waves within the room. You do not want the sound to bounce back and forth between two parallel walls. Those foam panels are good on the wall. One-by-one strips of wood or plastic mounted on the walls will also disrupt the sound waves from bouncing directly off the walls. Dispersing the waves with wood strips and foam will help to disapate them. This means the sound will not build up to deafening levels.

Carpet will be good on the floor. The deeper the better for sound purposes, but short enough to make it usable.

Best if the ceiling is not level, parallel to the floor. Corrugated metal or plastic on the ceiling and/or walls will help disperse the standing waves.

Research bass traps. Basically a large trash an in the corner of the room stuffed with insulation. This helps to keep the bass levels from accelerating out of control.

Ah yes sound TREATMENT. I'm afraid of this. Non-parallel walls and bass traps are what I keep hearing. There's a possibility we record in here and that is where proper design/treatment can make the room usable for recording loudish drums. Also ceiling height :/

 

[Old Man Roger]

I fast forward to the end of that video, the results were impressive.

 

[mike93lx]

Risk what? Double layer drywall wouldn't be time consuming, especially not compared to anything concrete. But it sounds like you already made up your mind here

 

[Bob_McPhee]

Risk what? Double layer drywall wouldn't be time consuming, especially not compared to anything concrete. But it sounds like you already made up your mind here

Oops sorry, I was agreeing with you. I meant why risk the cinderblock structure cracking my slab. My brother in law keeps insisting it will be fine but I've been leaning towards a framed drywall structure.

The drywall structure will be slightly complicated given that I'm going with a double stud wall construction in order to maximize low frequency isolation:

The pink stuff is cheap R13 insulation. The green stuff is green glue, an acoustic compound, sandwiched in between layers of 5/8 drywall. This is a proven method in studios and home theaters when low, rumbling, bass frequencies need to be isolated. Since I have plenty of space, building these double walls should be worth it. The ceiling is another matter, but I have a plan for that.

 

[mike93lx]

Oops sorry, I was agreeing with you. I meant why risk the cinderblock structure cracking my slab. My brother in law keeps insisting it will be fine but I've been leaning towards a framed drywall structure.

The drywall structure will be slightly complicated given that I'm going with a double stud wall construction in order to maximize low frequency isolation:

The pink stuff is cheap R13 insulation. The green stuff is green glue, an acoustic compound, sandwiched in between layers of 5/8 drywall. This is a proven method in studios and home theaters when low, rumbling, bass frequencies need to be isolated. Since I have plenty of space, building these double walls should be worth it. The ceiling is another matter, but I have a plan for that.

Ah, my bad.

Rockwool is a great product for sound insulation.

Also, FYI, you have to take the S out after http for images

 

[pmiranda]

I wouldn't even try a block wall on what is almost certainly a cheap, thin, floating slab. Even if by miracle the side and back wall footings are overbuilt, the inner and front walls will probably destroy the slab. You can do great things with lighter, easier to handle materials.

 

[In2toys]

Yep got the ceiling covered. Probably vertical 2x4 joists 10" apart. Either a layer of plywood or metal decking with around 2" of concrete poured. Got the idea from this guy:

cant believe i'm the first to notice this... concrete on top of the ceiling joists.?

 

[FANTM58]

Build a 6” wall using 2x4 stagger stud construction.
Rock wool insulation and quiet rock covering.

Foam and quiet rock on the exsisting walls

Exactly what I was thinking !

 

[JRC3]

I want to point out one thing...The OP is concerned about his neighbors and letting them enjoy the comforts of their own homes.

 

[ard]

cant believe i'm the first to notice this... concrete on top of the ceiling joists.?

yeah, lol.

A qualified expert, tasked with this project, would NOT be building a second block wall and would NOT pour a 2" concrete 'ceiling'.

A qualified expert would simply take the existing room and soundproof it. No muss, no fuss.

But there is something exciting about doing it 'wrong'...document it on youtube...'crazy man crazy'... all that stuff

 

[3onthetree]

It sure sounded like from your first idea of CMU w/poured ceiling you were building your band a crypt. Glad you came around to the double stud wall (I use this method for apartment party walls).

3 more inputs beyond what been said:
- Use "Safe'n'Sound" by Rockwool (formerly Roxul) which is 3" thick.
- Your door into this room will be the weak point. Unless you want to spend $1200+ on an acoustic steel door.
- Stay away from the eggcrate foam, in case one of you light up.

 

[madison069]

Have you actually listen from outside to see how much sound is being projected from the garage when someone is playing music?

My garage is cinder block with wood framed roof and asphalt shingles. It does have insulation in the attic space on the floor. The interior side of the garage was framed with 2x4 metal studs and fiberglass insulation between the studs. Then 1/2" drywall was laid on top of it all.

Garage doors appears to be insulated but I have no clue on the R value.

With all of this I can't hear the two air compressor running outside the garage. Can't imagine a musical instrument being louder then a direct drive air compressor and a belt driven air compressor running at the same time.

 

[Old Man Roger]

Have you actually listen from outside to see how much sound is being projected from the garage when someone is playing music?

My garage is cinder block with wood framed roof and asphalt shingles. It does have insulation in the attic space on the floor. The interior side of the garage was framed with 2x4 metal studs and fiberglass insulation between the studs. Then 1/2" drywall was laid on top of it all.

Garage doors appears to be insulated but I have no clue on the R value.

With all of this I can't hear the two air compressor running outside the garage. Can't imagine a musical instrument being louder then a direct drive air compressor and a belt driven air compressor running at the same time.

I suspect Bass, not necessarily volume level, is the problem here.

 

[Danno1]

It sure sounded like from your first idea of CMU w/poured ceiling you were building your band a crypt.


- Stay away from the eggcrate foam, in case one of you light up.

Can double as a tornado shelter...


Yes, foam is dangerous in a fire.


.

 

[56Safari]

Have you actually listen from outside to see how much sound is being projected from the garage when someone is playing music?

My garage is cinder block with wood framed roof and asphalt shingles. It does have insulation in the attic space on the floor. The interior side of the garage was framed with 2x4 metal studs and fiberglass insulation between the studs. Then 1/2" drywall was laid on top of it all.

Garage doors appears to be insulated but I have no clue on the R value.

With all of this I can't hear the two air compressor running outside the garage. Can't imagine a musical instrument being louder then a direct drive air compressor and a belt driven air compressor running at the same time.

Drums will carry much further than any air compressor.

I visited a studio once that built walls and filled them with sand... the loose sand absorbs the low end frequencies.. the room still required additional acoustic treatments for higher frequencies... I talked to one of the guys who helped Build it, sounded like a nightmare.. but just throwing it out there


Sent from my iPhone using The Garage Journal mobile app

 

[madison069]

Use to play tuba in the marching and classical band, so I know bass can travel. But thinking with that cinder block wall it shouldn’t take much more to muffle any little sound with some simple wall covering or 2x4 stud wall with fiberglass and drywall. I know material like carpeting does make a big difference in a room with none and it dampens the sound a good bit. But if there’s going to be drums in there then yea you’re going to have a hard time muffling that sound out.