One room basement studio design - build complete!

Hi all! I’m Jed. About seven years ago I built a tiny, one-person studio using the gracious advice and help of the patrons and moderators of this site. Thank you! I’m excited to be back here. I read the latest version of Rod's book about three times before I felt ready to make this post. My family moved this summer and it is time to start again on a new basement studio. Our ‘new’ house is a 1951 ranch in a residential neighborhood in Portland, OR. We have two neighbors that I would like to not bother, each approximately 10’ from the outside walls of our house. The studio would be one room in the basement of our house. The basement is 80% below grade and is conditioned space that stays around 60-65 degrees F in the summer. The studio would occupy about 25% of the total square footage in the basement. USAGE: The main purpose of the studio will be as a rehearsal space for my seven-piece ska and reggae band. I have not measured the loudness of our band when we practice but I would estimate 100-110dB. I will get a meter and measure the next time we have practice. I always wear earplugs because I’m the bass player standing by the drummer and he won’t let me take his cymbals away. You know how it goes. In addition to drums and bass we have an organ, an electric mandolin, a trumpet, a sax, and a trombone. Ideally I would be able to like to host practices or jam at night, on occasion, without bothering the neighbors or violating noise code (50db after 10pm). Daytime noise code is 55dB. The city measures using A weighting, fast response. The room would be used for full practice only about once a week for two-to-three hours. I would also use it at other times, let’s say 6 hours per week, for solo work. It would not be used commercially. Secondary purposes for the room are recording and mixing. I know it is a lot to ask from one room but I have to work with the space I’ve got. I was not considering angling the walls to conserve space since we'll be getting so many people in the room. I might be able to be convinced otherwise. BUDGET: Budget for the initial build is $2,000. I know it is not much. I and my friends will do most of the work ourselves. I am blessed in having a licensed contractor for a friend, a retired civil engineer and electrician for a father, and a brother-in-law that knows how to hang drywall. All of these folks are willing to help out. DESIGN STAGE AND ROOM DETAILS: I am at the very early thinking stages of this project and have not done anything other than tear down some wall and ceiling material in the space to see what I am working with. The space is in the basement, 80% of which is below grade. The floor is concrete (I don’t know the thickness but I do not intend to try and change the floor). The foundation walls are approximately 10” thick poured concrete. The space is in the middle-south section of the basement. Neighbors are to the east and west. South of the house is green space for approximately 200’. Approximate dimensions for the room: 84.5” high, 185” long, 131” wide. I've attached some rough drawings of the existing space (we just moved a month ago so there are still boxes and things in the space, hence no photos yet). The drawings aren't perfect (the width is off, need to fix that) but they identify the obstacles in the room. There are some upsides and some challenges. Upsides: 1. The room is pretty close to a couple good ratios 1:1.5:2.1 or 2.2 2. We’re 80% below grade. Challenges: 1. Ceiling height is obviously sub-optimal. Unfortunately that cannot be changed. 2. The existing water line and ducting. a. The water line has the shut off for the house and will have to be accessible. b. The ducting was poorly installed, including a major cut through one of the floor joists. It may be possible to change how or where the ducting is located, and to repair the cut joist. I will be working with a contractor to find out. If not, there will need to be some sort of soffit to cover the ducting. INITIAL IDEAS AND QUESTIONS: 1. I’m trying to determine the best approach for isolation at this time and am not yet considering the interior design and treatment. A box within a box is doable for the walls. A sealed double door setup will work. The low ceiling rules out a separate ceiling. From research it seems the best that can be done with the ceiling would be to add mass between the joists to the existing floor and then hang drywall from the appropriate kind of resilient channel. I’m working with my father to see what kind of load should be possible to add on the existing joists or if they would need to be beefed up. 1.1. Question: Is the above a reasonable approach or is there a better solution? 1.2. Question: Is, as I presume, the ceiling the lowest common denominator? 1.2.1. Question: As I understand things, the lowest common denominator determines the overall result of the room. Is this correct? (E.g. I could build walls with a higher TL than the ceiling but it wouldn’t matter, so I should build the remainder of the structure to at least match the TL of the weakest link. Is that correct?) 1.2.2. Question: If it were possible to add 2-3 layers of drywall to the subfloor between the joists, insulate, and hang 2-3 layers from resilient channel, what kind of isolation is possible? The STC chart (http://johnlsayers.com/Recmanual/Pages/STC%20Chart.htm) doesn’t exactly lay out this scenario but it appears it should be in the 55 range if 3 layers of drywall can be hung in both places. 1.2.3. Question: How many layers of drywall can one hang from resilient channel before taking out a new life insurance policy??? (Assuming the joists can handle the load.) 2. As I mentioned above, the basement is conditioned space. In the summer the basement is cool. In the winter I’m wondering if I could heat the room with a space heater before practice. 2.1. Question: With the relatively low usage of the room can I get by with just a ventilation system that recirculates basement air through silencers? 2.2. Question: Do you think humidity will be a problem with only 2-3 hours per week of typical usage with the full band? 2.3. Question: I calculate ~150cfm of airflow to be necessary. Does that sound right? That's all for my first post. I thank you all again for being such and amazing resource! Jed

Photos of the existing space:

Hi Jed, and Welcome back! :)

I have not measured the loudness of our band when we practice but I would estimate 100-110dB.

I'd guess more like 115dB - 118dB. A band with drums and bass is probably going to be in that area.

... and he won’t let me take his cymbals away.

:shot: :!: :D I know the feeling! :)

Ideally I would be able to like to host practices or jam at night, on occasion, without bothering the neighbors or violating noise code (50db after 10pm)

So you are talking about something like 60 to 65 dB of isolation. Not easy to achieve. Not impossible, but not a piece of cake either.

The floor is concrete (I don’t know the thickness but I do not intend to try and change the floor).

Concrete is great, and slab on grade is even better. Nothing to change there.

Approximate dimensions for the room: 84.5” high, 185” long, 131” wide.

Ouch. Only 7 foot ceilings? You are going to loose several inches there for the isolation, so I hope there's no tall players in your band!

The ducting was poorly installed, including a major cut through one of the floor joists.

Cut joists are bad news: that does indeed need to be repaired.

From research it seems the best that can be done with the ceiling would be to add mass between the joists to the existing floor and then hang drywall from the appropriate kind of resilient channel.

That probably is your best bet, but I wouldn't go hanging anything from those joists until you: a) properly repair the one(s) that are cut, and b) get a qualified structural engineer to make sure that you can add that much extra load to the joists.

1.2. Question: Is, as I presume, the ceiling the lowest common denominator?

Probably, but don't forget HVAC, doors, and your electrical system, as well as other potential flanking paths.

1.2.1. Question: As I understand things, the lowest common denominator determines the overall result of the room. Is this correct? (E.g. I could build walls with a higher TL than the ceiling but it wouldn’t matter, so I should build the remainder of the structure to at least match the TL of the weakest link. Is that correct?)

That's about right, yes. But there's also no need to "water down" otherwise good walls just because you suspect that your ceiling might not be up to the same level. You should still design each part to be as good as it can, without going overboard.

1.2.2. Question: If it were possible to add 2-3 layers of drywall to the subfloor between the joists, insulate, and hang 2-3 layers from resilient channel, what kind of isolation is possible?

That depends on many factors, but IR-761, IR-811 and IR-766, should help you to understand walls and floors. Also, STC is not a good method for determining studio isolation, since it does not take into account low frequencies. It's better to consider the full transmission loss curves, rather than STC.

doesn’t exactly lay out this scenario but it appears it should be in the 55 range if 3 layers of drywall can be hung in both places.

Might be possible, if Murphy happens to be on vacation!

1.2.3. Question: How many layers of drywall can one hang from resilient channel before taking out a new life insurance policy??? (Assuming the joists can handle the load.)

Better check that with the manufacturer of the RC that you plan on using, as well as your local building code, and your qualified structural engineer.

2.1. Question: With the relatively low usage of the room can I get by with just a ventilation system that recirculates basement air through silencers?

Doubtful. You say you want to have "several people" in that room at the same time, for several hours: Musicians put out a lot of humidity when they are "inspired", as well as a lot of heat. I doubt that just ventilation id going to cut it. But check Rod's book, in the chapter on HVAC: he shows you how to calculate all that stuff.

2.2. Question: Do you think humidity will be a problem with only 2-3 hours per week of typical usage with the full band?

Yep.

2.3. Question: I calculate ~150cfm of airflow to be necessary. Does that sound right?

What factors did you take into account with your calculations? - Stuart -

Thank you, Stuart. I'm off to do more research. Your thoughts on HVAC are a big concern, especially for budget.

Alright! So things have progressed in the planning and I’ve got drawings to share (see "plans" attachment below the baffle drawing). Here is the current state of the design: Loudness/Isolation: After measuring, Stuart was almost exactly right. At our loudest we are 114dB. However we do average more around 110. But then our drummer gets excited. The proposed design below isn’t going to get the full isolation I would hope for but it is as much as I can afford. We should get between 40-50dB I think if it all is done well. Most of the time that should be enough to keep us on the good side of the neighbors. Walls: All walls except the foundation wall will have two layers of 5/8” drywall added between the existing joist. Cavities will be filled with R15. Two additional layers of 5/8” drywall will be hung on RC-1 on the existing studs. Backer rod and caulking all around. Ceiling: No additional drywall added between joists. Too bad but it can’t be done without a lot of additional cost for structural reasons. Cavity filled with R15. Two layers of 5/8 drywall hung from Hat Channel suspended on RSIC-1 clips. Green glue between the two layers of drywall. Backer rod and caulking. HVAC: 12,000 BTU mini-split system to be installed in adjacent guest bedroom (garage conversion). Total wattage for people, gear, and lighting is calculated to be 4,400 watts (or 15,000 BTU). I’m sizing down slightly for longer run times for additional dehumidification. Fantech FG5 installed in ceiling joists of guest bedroom with 5” ducting into silencers/baffles behind furring wall on the foundation wall side of the studio. Fan will be pulling exhaust air out of the studio. Passive return air will go through identical ducting / baffles. This will provide 9 air changes per hour. Door: Still TBD, but down to one door, not two. Solid core minimum, maybe a “super door.” Either way it will get the full gasketing treatment all the way around. Electrical: Everything in the studio will be surface mount in pvc conduit. Questions: 1) Any red flags from the above? 2) Can someone take a look at my baffle design and see if it makes sense? The inlet duct is 5” in diameter. The out vent will be 8”x18” with 80% open area. I calculate 195 feet per minute at the register (down from 1,147 in the 5” duct). Not perfect according to Rod’s book but that should be pretty quiet, right? The wall the baffles will be behind is very shallow so this is a really skinny design. Any problems with doing things this way?

After measuring, Stuart was almost exactly right.

:!: Sometimes I get lucky! :)

However we do average more around 110.

That's pretty loud. I hope you guys are wearing hearing protection! According to OHSA tables, you will suffer irreversible hearing damage at that level in about 30 minutes.

We should get between 40-50dB I think if it all is done well.

Sounds like a realistic goal. Certainly do-able.

Door: Still TBD, but down to one door, not two. Solid core minimum, maybe a “super door.” Either way it will get the full gasketing treatment all the way around.

If you hope to get 50 dB of isolation, it will have to be a superdoor, and very, very massive. It's really hard to get that kind of isolation with only a single door.

2) Can someone take a look at my baffle design and see if it makes sense? The inlet duct is 5” in diameter. The out vent will be 8”x18” with 80% open area. I calculate 195 feet per minute at the register (down from 1,147 in the 5” duct). Not perfect according to Rod’s book but that should be pretty quiet, right? The wall the baffles will be behind is very shallow so this is a really skinny design. Any problems with doing things this way?

That looks like it should work fine, but you seem to be off on your calculations. A 5" duct has a cross sectional area of about 78 square inches, and the outlet is going to be 144 square inches (8" x 18"), so you will be reducing the flow by a factor of about 1.84. If you have a flow rate of 1,147 cfm in the inlet, that will get down to about 621 at the outlet. You will need to add something else to reduce the flow rate before it gets to the inlet of your silencer, or build a silencer with a much greater cross sectional area. What I do sometimes is to feed the center of a silencer like yours, and allow the air to flow out both ways, both left and right, and take that to two registers. That effectively doubles the cross sectional area, so in your case you'd bee down to a flow rate of about 320 at each register. If you add a 2:1 flow reducer in the 5" duct, you would then be fine, with a theoretical outlet velocity of 160 cfm. Hope that helps! - Stuart -

Hi Stuart, Thanks very much for the advice. A super door is probably do-able. Looks to be a pain but what else is new. I'm going to quibble with your math on the area of a circle. I think you may have typed 5 for the radius, but that would be a 10" duct, no? Cross section of 5" duct should be ~19", right? :wink: Regarding earplugs --- I ALWAYS wear them, as does as organ player. I can't even be in the room with our drummer without them on. The rest of my band mates are hopeless. I bought them all the nice etymotic earplugs for christmas two years ago. No use. Personally, I wan't to be able to hear what my grand kids are saying when I'm an old man. j

Cross section of 5" duct should be ~19", right?

Yup! :oops: - Stuart -

No worries! Measure twice cut once. Do you have any ideas for duct liner? The commercial products I've see look very expensive. Some folks have suggest fiberglass covered with plastic. Rod's book is silent on this. Thanks again! Jed

Hi all, Just a quick update as my room's construction is now complete. I'm still perfecting the door seals and I need to build treatment but I did a quick test yesterday to see how much isolation I was able to achieve. I'm a bass player with a big amp for playing out. I played some of our bands music through it and heavily compressed it to keep the loudness up. On my meter I got it up so that it was hovering around 110dB (I was wearing earplugs). The bass was pounding me in the chest and it was really, really loud, even with earplugs in. I closed the door and went upstairs...wait for it...I measured 55dB on the meter. Stepping out of the house the sound was completely inaudible from about 5 feet past my front door. I am ecstatic with this result. I'll try to get some photos of the build up at some point and some more when treatment is finished. J

That's good news, Jed! :thu: I certainly think we can mark this as a successful build! 55 dB isolation is an excellent achievement, especially considering we are talking about heavy bass. This certainly proves that good isolation can be achieved when people do things right. Congratulations! :) Can't wait to see the photos! - Stuart -