Unconventional build in a detached garage..

I'll try to make this as simple as possible. I might be wrong but I feel like my constraints are rather simple in my situation. I live on unrestricted land outside city limits so I have no code constraints. My goal is to create a practice area for a full band. I'm not concerned too much about the acoustics of the room. I just want a place where a band can jam or be loud after hours without disturbing people in the house. Here's a detailed description of the situation Garage Dims 20 X 24, 8’ walls, typical pitched metal roof, 1 man door on front right side, 1 overhead door approx. 15’ at front and one window at rear approx. 3’ X 4’ Walls 2 X 4 studs on 16” centers with what I believe is 5/8 plywood outside and vinyl siding on top of that. (no insulation and no Sheetrock inside) Floor Concrete slab that butts up to my driveway When jamming I took readings at a max of 107db in the center of the room In the areas of the house nearest the garage I'm taking readings of 93db max (Goal is 30). So right now I'm only getting a reduction of 14db which sounds about right as the huge roll up sheet metal door is pointed directly at the house. I feel like I don't need a lot of isolation to achieve the desired results. I feel just framing in the door and window with a single leaf wall will help out immensely. So I have some rather unconventional ideas for this project using some second hand materials I have on hand. I plan on going above and beyond and doing a double leaf system with and 7" or 8" air gap and fiberglass isulation. I have plenty of second hand 2x4s that I could frame out the walls and ceiling with. I also have obtained a massive about of 2' x 3' x 3/4" MDF sheets enough to do 1 layer on all of the walls (I'll just use sheet rock on the ceiling). Now I know this would be a massive undertaking with caulking all the seams.. But I cant see paying for all the required sheet rock when I have this great MDF on hand. Thats why I'm looking for ways around caulking all the seams.. Yes I said it before, unconventional.. No building code.. So the caulking is for sealing the assebly airtight right? What if I butt the MDF up with no gap and use somthing like these huge roll of neoprene we use at my work 1/4" x 4' and glue it to the walls. 2 long pieces cemented together would handle 1 wall and it would be totaly sealed.. Or.. I could just glue strips along the seams if complete coverage would cause moisture problems.. Just thinking out of the box for a simple jam space Any thought on this? Does the sound reduction I'm looking for sound possible with what I'm suggesting? Also what suggestions for heating and cooling would you guys make with me being in North Texas for this type of space? Thanks, Paul

BTW the first reading I took was too close to the garage. I did it again right outside the house and I'm coming up with 72. I forgot to mention also. On the outside I will be pulling the siding off and adding another layer of osb all around. And I will use a double door system sealed with gaskets

I live on unrestricted land outside city limits so I have no code constraints.

Hmmmm... I'm not so sure about that! :) There might not be any additional local code limitations, but there are still national building codes to comply with. For example, you can't just decide to wire up the electrics any old way: you are still subject to electrical code requirements, regarding conductor cross section, circuit breakers, grounding, voltage drops, dsitance, etc. You are still also subject to legal structural requirements, too: You can't decide that you'll just use 2x4 ceiling joists to span 30 feet with three layers of drywall :!: :shock: : you still have to follow code for that. Ditto for fire codes, plumbing, seismic, etc. So I'd suggest that you should do some more checking, and find out exact which ones you are subject to, so you can make sure you meet them. Or hire an architect to do it for you.

My goal is to create a practice area for a full band. I'm not concerned too much about the acoustics of the room.

If interior acoustics are not an issue, then just build the place out of 1 foot thick concrete on all sides! Good isolation, but lousy acoustics. However, I strongly suspect that you'd change your mind very rapidly about the need for good acoustics, the very second you step inside and hear how awful that sounds! :shock: :lol: In other words, you should probably think that part through again: If the acoustics are lousy inside the room, then nobody will want to jam in there.

Floor Concrete slab

That's a really good start!

Walls 2 X 4 studs on 16” centers with what I believe is 5/8 plywood outside and vinyl siding on top of that (no insulation and no Sheetrock inside)

Excellent! An unfinished garage with a slab-on-grade floor. That can easily be built out to a proper two-leaf MSM system.

When jamming I took readings at a max of 107db in the center of the room. In the areas of the house nearest the garage I'm taking readings of 93db max

So you are basically getting no isolation at all currently: Not even as good as an average house wall. 14 dB is very poor isolation.

max of 107db ... Goal is 30

So you need 77 dB of isolation? That's a really tall order. Not impossible, but not easy to attain, unless you have a very good budget.

I feel like I don't need a lot of isolation to achieve the desired results.

:shock: Unfortunately, your "feeling" here is dead wrong. Achieving 80 dB of isolation is a MAJOR undertaking. Not many home studios aim for that, and even fewer achieve it. That's the type of isolation that professional studios aim for, and even they have a hard time achieving it. 80 dB isolation is extremely hard to do. And expensive. To put this in perspective: An average house wall built from 2x4 studs with 1/2" drywall on each side, achieves about 30 dB of isolation. Increasing that to 40 dB means that you have to stop TEN TIMES as much energy. Increasing the isolation from 30 dB to 50 dB means you have to block one hundred times the amount of energy. Going from 30 to 60 is one thousand times the amount of energy. Going from 30 to 70 is ten thousand times as much energy. And your goal of going to 80 dB of isolation means that you have to block one hundred thousand times as much energy as a typical house wall. What many people don't realize is that the dB scale is logarithmic, not linear, so large dB numbers mean VERY large amounts of energy. So basically you are setting yourself a goal of building a wall that blocks one hundred thousand times more energy than a typical house wall. That is not easy to do, and takes a lot of money.

I feel just framing in the door and window with a single leaf wall will help out immensely.

Sorry, but it wont. It wont help "immensely", and it won't even help moderately. At best, it will help mildly. VERY mildly. Here's the thing: if you build a single leaf wall, you are limited by a law of physics known as "mass law". Basically, what that says is that each time you double the mass of a wall, you get an increase of 6 dB in isolation. That assumes theoretically perfect mass, but in real life it is more like 4 to 5 dB for each mass doubling. So with mass law in mind, let's take a look at that typical house wall again, and see what you'd need to do to it to get more isolation: Mass law says that we have to double the mass. The basic house wall has two layers of drywall on it, so we add another two, for a total of four layers. Mass law says that will increase the isolation by 5 dB. So now we have 35 dB of isolation, instead of 30 dB. Great. Do it again: to double the mass again, we have to add another four layers of drywall, for a total of eight, and now we get 40 dB of isolation. Double again gives us 16 layers of drywall and we get 45 dB. Double again; 32 layers gives 50 dB. And again: 64 layers = 55 dB, 128 layers = 60 dB, 256 layers = 60 dB, ... I think you see where this is going. Mass law is NOT your friend! Single leaf walls do not provide useful isolation, because the decibel scale is logarithmic, not linear, and high levels of isolation are BIG numbers. If you want the actual equation for mass law, here it is: TL(dB)= 20log(M) + 20log(f) -47.2 M is the surface density of the leaf, and f is the frequency. There's a simplified version based on empirical measurements of real-world isolation, across the entire spectrum (not considering frequencies), that goes like this: TL(dB) = 14.5 log M + 23 dB where: M = Surface density in lb/ft2 Using that equation, to get 80 dB of isolation, the surface density of your wall would have to be about 10,000 pounds per square foot. In other words, looking at each square foot of the wall from the front, there would have to be enough mass in the thickness of the wall behind that square foot to add up to ten thousand pounds. The density of concrete is about 3600 pounds per cubic yard, so your wall would have to made from reinforced concrete about 2.8 yards thick, which is about eight feet thick. (Steel is about 4 times more dense that concrete, so you could do it with steel plate about two feet thick). You are grossly underestimating what it takes to achieve 80 dB of isolation with a single leaf wall...

I plan on going above and beyond and doing a double leaf system with and 7" or 8" air gap and fiberglass isulation.

This is a MUCH better plan. Two-leaf MSM walls offer greatly increased isolation, as compared to single-leaf walls. You can get much better isolation with much lower mass, and much less thickness. It is still not easy to get to 80 dB of isolation, but it's an awful lot more feasible that with a single leaf.

But I cant see paying for all the required sheet rock when I have this great MDF on hand.

MDF is fine. It's actually a bit more dense than drywall, which is good, and yours is 3/4" MDF, which is even better. However, even with an 8" air gap, you'll need a lot more than just one layer of MDF on your inner-leaf, to get 80 dB of isolation. I haven't done the math (it's a bit more complex than for single leaf), but I'd guess that you'd need four or five layers on each leaf, at least, to get that high.

Thats why I'm looking for ways around caulking all the seams..

Why? If you don't seal the gaps, then you don't have good isolation. Good seals are critical for isolation. The more isolation you need, the m¿better the seals have to be......

So the caulking is for sealing the assebly airtight right?

In part, yes. But it is also for maintaining the continuity of the mass. Mass is also critical for isolation, so it the wall is not built as one continuous, seamless chunk of mass, with the same density all over, then you will not get good isolation.

What if I butt the MDF up with no gap and use somthing like these huge roll of neoprene we use at my work 1/4" x 4'

Then your isolation would be limited by the surface density of the neoprene. And sheets of neoprene are also rather more expensive than caulking. Then you have to add the cost of the glue, and I'm not even sure how you'd glue that: contact cement, I guess. And how would you ensure that the glue did not crack over time, or come unstuck in places, thus trashing your isolation?

Just thinking out of the box for a simple jam space

What makes you think that gluing two layers of neoprene rubber to all of your walls, would be simpler than just caulking the joints? I very much doubt it would be simpler, and it certainly would not be cheaper...

Does the sound reduction I'm looking for sound possible with what I'm suggesting?

No: Take a look at this publication to get an idea of what it takes to get 80 dB of isolation: http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir761.pdf I'll give you a hint: that paper analyzes about 300 different types of wall construction. The were all tested in an advanced acoustical test laboratory, to see how much isolation each type gets, in the real world. The very best wall gets only an STC-69 rating (which does not mean 69 dB). It's a LOT harder to get high levels of isolation that you imagine.

Also what suggestions for heating and cooling would you guys make with me being in North Texas for this type of space?

First you'll need to figure out the heat load in your rooms, based on occupancy (how many people will be in there) plus equipment (how much heat your gear puts out) and lighting (how much heat your room lighting puts out). That's called the "sensible heat" load. Then you need to figure out the latent heat loading for your area. That's how much energy it takes to remove the humidity from the air, before it actually starts cooling down, or in simpler terms, how much energy your HVAC system will waste in just condensing the water vapor in the air without changing the temperature. The sum total of sensible heat ant latent heat loading is how much cooling capacity you need, and is expressed in BTU/Hr. So you need to know that to decide on the capacity of the HVAC system that you need. Do NOT get one that is too big or too small! That's a major mistake. If you get one that is too big, then it will have a very short duty cycle, and the temperature and humidity will jump up and down all the time. Unpleasant. If you get one that is too small, then it won't be able to do the job: it will stay running full time, use a lot of power, fail frequently, need a lot of maintenance, be noisy, and leave the room too hot and too humid. So do the calculations carefully, then get the right size unit. That's for the "AC" part of HVAC. You won't need much "H", and that is implicit in the AC anyway, so don't worry about it. That just leaves the "V", which is critical. You do need to breathe inside, so you need to bring in fresh air and exhaust stale air. So here to you need to do the calculations to figure out how much air you need (air flow rate), staring with "room changes per hour", multiplied by room volume to give you cubic feet per hour, divided by 60 to give you cubic feet per minute, since that's what most fans are rated as. Then you need to figure out the duct sizes that you will need, based on the flow rate and considering that the flow velocity cannot exceed 300 FPS at the register, and is hopefully much lower. You do that by calculating the cross-sectional area of the duct that will allow that correct volume of air to flow to flow at a speed lower than 300 FPS. Then you need to figure out the static pressure that your duct system will have, so you can figure out which fan is able to give you the correct flow rate when running against the static pressure imposed by your system. And finally, you need to figure out the dimensions of your silencer boxes, based on all of the above and also on your need for very high levels of isolation. Your silencer boxes will have to be very large, and very thick walled, to get that level of isolation. You need one such box on each place where a duct goes through a wall leaf. It's a bit more complex than that, but there you have the simplified "over view" of how to do it. For the actual HVAC equipment, you can use either several mini-split units (one in each room) or a central AHU in the duct system, that handles all of the rooms together. - Stuart -