John Sayers' Recording Studio Design Forum Archive

Hi guys. I'm in the planning phase for the construction of a drum practice room. I have a good contractor on the hook to help me with the construction and we have a superficial understanding of what is required, but I'm realizing there are a bunch of factors I didn't appreciate (e.g. triple leaf effect). Anyway, my overriding concern is with keeping drum noise from escaping out and annoying the neighbors.

The starting point room is a 9.5 x 9.5 x 8.5 (H) foot room in a garage on a concrete slab. There is one door into the room from the interior and a window on the opposite wall, which I'm willing to lose. The room is currently finished with one layer of drywall and insulated. The room is at the corner of the structure so has two interior and two exterior walls. Exterior walls are minimalist 2x4 stud construction with fiberboard sheeting. Noise to the inside of the garage is of minimal consequence, so I need to keep sound from escaping through the exterior walls, or penetrating the interior walls AND the other garage walls, OR escaping out the ceiling and roof. The ceiling leads to a traditional A-frame rafter attic situation. The interior walls are currently insulated with rockwool and the exteriors have blown-in insulation. The ceiling has R30 denim batts.

My going in thought was that I would build a free standing room within a room and put two layers of drywall with green glue on the inside. I started researching and quickly was informed that I'm setting up a triple leaf problem with that design. I'm unclear how to remedy this though, given that the exterior wall is lightweight fiberboard construction.

Any suggestions for how to deal with this would be great, or other general suggestions on how to do this properly. Thanks.

Welcome Mastiff!

Here was a room my buddy built with the exact same requirements as yours. His was in his basement but required the same build out as yours would:

http://www.johnlsayers.com/phpBB2/viewt ... 10&t=21704

There is one door into the room from the interior

You will need 2 doors. One for your outer leaf and one for your inner leaf. You can see how to build a door in the link above.

and a window on the opposite wall, which I'm willing to lose.

Filling in the window would be the cheapest solution. If money and the level of build out complication isn't an issue, then keep it as natural light is great.

The room is currently finished with one layer of drywall and insulated.

You can re-use the insulation, but you will have to rip out and dispose of the drywall.

Exterior walls are minimalist 2x4 stud construction with fiberboard sheeting.

You will have to "beef up" the exterior sheathing in order to make it your required surface density. You can use this calculator to see how much surface density (and really, what materials you can use to obtain said surface density) and how much space to leave between your sheathing or framing:

Gregwor & audiomutt’s MSM Transmission Loss Calculator Version 2.03

Noise to the inside of the garage is of minimal consequence

Isolation is not a one way street. It's all or nothing.

The ceiling leads to a traditional A-frame rafter attic situation. The interior walls are currently insulated with rockwool and the exteriors have blown-in insulation. The ceiling has R30 denim batts.

If ceiling height is a concern for you, you could gain 1.25" by building modules that go into your rafter joists, ultimately making your sheathing flush with them. This would be your outer leaf ceiling.

Your inner leaf ceiling should be done inside out (like the link I posted above) as it will both make your ceiling height as tall as possible and make your room sound the best that it can.

My going in thought was that I would build a free standing room within a room and put two layers of drywall with green glue on the inside. I started researching and quickly was informed that I'm setting up a triple leaf problem with that design. I'm unclear how to remedy this though, given that the exterior wall is lightweight fiberboard construction.

Correct.

Before anything, figure out your ventilation system! You will see in the post I linked above how big HVAC silencer boxes are. You cannot have the isolation you require without having an air tight room. You cannot survive inside of an air tight room! Then:

1. rip out the existing drywall
2. fill your window (if you want to save money) and make the exterior look nice
3. "beef up" (that the term used around the forum) your exterior sheathing
4. beef up your interior wall outer leaf sheathing (the easiest way is to add mass onto the outside of the wall where the studs are not exposed. You'll see how much of a pain in the ass it is to beef up on the stud side of the wall using cleats and such.
5. you'll probably want to adjust the width of your door opening because using a proper bank vault style sealing system on your door ultimately reduces the usable width of the door.
6. build and place your HVAC silencer boxes.
7. prep your electrical/mini split "umbilical cord"... Not sure what else to call the condensor unit bundle of crap.
8. build your inside out walls and stand/connect them.
9. install your inner leaf ceiling joists.
10. build and install your ceiling modules.
11. finish up your electrical
11. build and install your doors.
12. acoustically treat your room.
13. cosmetically finish your room with flooring/fabric/trim, etc.

I probably forgot something on that list, but hopefully it gets the wheel spinning in your brain on how to build your room!

Greg

Thanks for the thorough reply!

Regarding the outer leaf, what I have now is probably 1/4" or so sheeting (Arizona). Is there any practical way to really beef that up and have it feather into the rest of the structure? I could put 3/4" MDF on the outside walls, but it would bump out with respect to the rest of the outer wall. If I understand, the alternative is to cut to fit many pieces of drywall (or MDF) and insert between the studs all around, right?

I think I understand the inside-out ceiling, but are you suggesting that also for the walls? This would make the gap between leafs smaller, which I thought was a bad thing.

Finally, regarding HVAC, the link was enlightening. I've been using the room with no real ventilation for a while and I can live with it for the small periods of time (a few hours at most between breaks) but it's not ideal, especially in the summer. The adjacent area, out the door, is a slightly larger finished room with a mini-split that is plenty over powered for the amount of area. What do you think about putting a couple muffler boxes in the attic and simply circulating a bit of air back and forth to the adjacent room with a fan?

Regarding the outer leaf, what I have now is probably 1/4" or so sheeting (Arizona). Is there any practical way to really beef that up and have it feather into the rest of the structure? I could put 3/4" MDF on the outside walls, but it would bump out with respect to the rest of the outer wall. If I understand, the alternative is to cut to fit many pieces of drywall (or MDF) and insert between the studs all around, right?

The bump out would be unsightly for sure! If you're not willing to do that, then the only way is to "beef up" the inside within the wall studs as you mentioned. Do not glue and screw the new sheathing material onto the existing 1/4" sheeting. Use green glue and cleats. If you use the search feature on the forum and search the word "cleat" or "cleats" you will see what I'm talking about. Personally, when I've used cleats, I put a good dab of caulk on the cleat before installing it. You can use any material for this beef up. OSB might work best for the exterior walls as that material is a bit more resilient to weather and moisture than MDF is. The one downside to OSB is that it does indeed have less surface density than MDF so you will need slightly thicker material. But we are talking fractions of an inch here only.

I think I understand the inside-out ceiling, but are you suggesting that also for the walls? This would make the gap between leafs smaller, which I thought was a bad thing.

You are correct that smaller gaps are worse. However, the calculator I linked you has an option for "inside out" to help you sort out your wall design. AND, in the end, you actually end up with a larger room. This is because you won't have to install any additional acoustic treatment devices to the exposed sides of your walls! So, in the end, all your room will have is sheathing and your framing. That's it. If you were to build a traditional wall, you would have framing, sheathing, then your treatment devices! This also complicates the build and results in a lot more material. This means more $$$ and time! Inside out is a brilliant idea created by the brilliant mind of John Sayers himself!

Finally, regarding HVAC, the link was enlightening. I've been using the room with no real ventilation for a while and I can live with it for the small periods of time (a few hours at most between breaks) but it's not ideal, especially in the summer. The adjacent area, out the door, is a slightly larger finished room with a mini-split that is plenty over powered for the amount of area. What do you think about putting a couple muffler boxes in the attic and simply circulating a bit of air back and forth to the adjacent room with a fan?

Sadly, an oversized unit is a bad thing. It could be short cycling! I'm not recommending it, but you COULD maybe pull conditioned air from the other space into your recording room and then dump the stale air outside.

As I'm sure you've seen on other threads on the forum (assuming you've spent countless hours on here researching and learning) as well as Darren's drum room build that I linked before, HVAC silencer boxes are LARGE. In fact, the larger they are, the more insertion loss they provide. We need lots of insertion loss. So, when you design yours, make sure they are massive. Often, finding a place for them is difficult. Darren's work great, but really, I think we should have added more baffles to his 3 little ones in his ceiling. He would have benefited more if they were longer. His 3 big ones are awesome though! The reason I say this is because once they were built, even yelling through them, the difference between the big and small ones was drastic.

Thank you for even considering your ventilation though. A lot of people shrug it off as a silly detail when in reality, it is probably the most important and complicated part of a proper safe room. There's a reason there are so many laws and rules (see ASHRAE) in regards to home and business HVAC.

Greg

Gregwor wrote:You are correct that smaller gaps are worse. However, the calculator I linked you has an option for "inside out" to help you sort out your wall design. AND, in the end, you actually end up with a larger room. This is because you won't have to install any additional acoustic treatment devices to the exposed sides of your walls! So, in the end, all your room will have is sheathing and your framing. That's it. If you were to build a traditional wall, you would have framing, sheathing, then your treatment devices! This also complicates the build and results in a lot more material. This means more $$$ and time! Inside out is a brilliant idea created by the brilliant mind of John Sayers himself!

I see. The exposed studs provide nearly unlimited options for surface treatments that don't have to extend into the room. Just playing with the spreadsheet, it looks like it will cost me 5-6 dB at low frequencies to flip the wall like that. I'm assuming when "inside out" is selected though, it makes it so the end of the 2x4s is where the face of the drywall was in the non-inside out scenario? If so, it's not quite apples to apples since the surface treatments would indeed take up space... but having said that, according to the sheet, I pretty much have to increase the gap by 3.5" (2x4 depth) to get the low frequency attenuation back, and I think I'd rather have handful of strategically placed treatments in place than making the whole room 3.5" smaller all around. Am I thinking about this right?

EDIT: I forgot to ask about the concrete slab. I'm hoping for my application, I don't really need to worry about that as an acoustic path. Right now I have industrial rubber backed carpet squares on the floor. What is best practice regarding the contact point between the inner walls and the floor/slab? I was thinking of simply setting it on the existing carpet to semi-float it, is that a bad idea?

Thanks again.

I think I'd rather have handful of strategically placed treatments in place than making the whole room 3.5" smaller all around.

If that's what you prefer. I personally don't like the idea of hanging panels around the room for both visual reasons and acoustic reasons. And moreover, due to the extra cost.

Am I thinking about this right?

Yes

Right now I have industrial rubber backed carpet squares on the floor.

Those will probably be fine to use for your floor.

What is best practice regarding the contact point between the inner walls and the floor/slab?

John prefers to float the walls and if you can do it properly, I'm with him. But personally, I see too many chances of screwing it up to even try. First off, calculating the weight of the inner room (including any future treatment you may install) in order to achieve proper deflection of isolation pads seems really intense to me. Also, the extra cost deters me. Lastly, installing the wall onto lag bolts that won't flank seems almost impossible to me, especially when installing an inside out wall. If you stick framed it as a traditional wall then maybe. Otherwise, just use a ton of caulk (like 3 huge strips of it) between your floor and sill plate.

I was thinking of simply setting it on the existing carpet to semi-float it, is that a bad idea?

The carpet won't do anything short of maybe allowing sound to leak out. It will squish completely and not float whatsoever.

Greg

I wonder about the alternative of building a new free standing structure. I have plenty of property for this purpose, and it would have the advantage of being further away from any neighbors instead of right next door as is the current space.

So the question: I'm looking to have a sound isolated practice space for drums, with growth potential to lightweight recording. 12-15 foot square of usable interior space would be desired. How would you construct a freestanding structure for this purpose? Things that come to mind are that I could build the outer structure of concrete block and have a very large air gap to the interior space. I'm thinking like a walkway (narrow hallway) around the outside, that would actually look nice-ish with an inside-out wall for the inside room.

To the extent the calculator matches reality, a concrete block structure with 24" air gap and inside out interior room with double drywall will provide massive attenuation. The calculator shows 90 dB over most of the range and above 75 dB everywhere. Practical reality may intrude on this, but it seems like a good start. There is, of course, the ceiling/roof to manage as well, which would probably be the weak link.

Any other ideas or suggestions?

Concrete block is not the sound reduction medium most people think it is. Sound is air pressure and concrete block has a lot of air, as does the mortar holding them together.

A simple 4 x 2 outer frame lined with a layer of OSB and a decorative liner will suffice as the outer skin.

Build an inside/out inner skin with a layer of fire rated plaster and you can play drums and record at any time during the day or night.

Leo did exactly that and he's doing just that.

http://www.johnlsayers.com/Pages/thirdeye.html

cheers
john

Thanks for all the help. I think I've been made aware of a number of pitfalls I was ready to fall into.

Another topic: What are the best practices for windows? My small space (not the freestanding option) has a window currently. How would you recommend I keep that with the room in a room design, assuming it can be done without compromising the isolation?

EDIT: Another question for you gurus: What should I choose for stud spacing on the inside room? I did some surfing and it kind of looks like bigger spacing is better, but the sites didn't mention frequency. Intuitively, a stiffer wall seems like it would pass more high frequency and a floppy one would pass low frequency. I think my biggest challenge is at the low end.