Massachusetts Single Room Basement Project Studio

After an almost two year hiatus I am back to working on my one-room basement project studio/office. I have a deadline now; our second child is due in November and I have to move my office out of the upstairs bedroom I'm now occupying. This also means I have full spousal support to get this done, so I'm anxious to finally get going! My isolation need are primarily from the upstairs - directly above and bedrooms two floors above. Isolation from neighbors is not a big concern as this room is behind a hill and other houses are not close. Ideally I would like to support live musicians playing with TV watching possible in the room above, and children sleeping two floors above. I have a pretty good basic understanding of MSM at this point. My plans are to build a completely independent room-in-a-room including a fully independent ceiling. But of course I still have many questions which I hope folks here will be able to help me with. My basement is a walk-out so the wall to the front of the house is 10'4" tall (below grade), but to the rear the basement wall only comes up 31" from the floor and it's wood frame exterior walls from that point up. Some pictures to illustrate: And here's my basic plan for the new walls: On the south side is an existing wall closing off this area from the rest of the basement. When I put up this wall four years ago I used what I then thought was good sound isolation practice (I hadn't found this forum yet to learn better) - it's an offset stud wall on a 2x6 plate with homasote under the sheetrock. I foolishly finished both sides of the wall thinking it would give me a head start on finishing the studio area. Now I need to remove the sheetrock (and homasote) on the studio side as that wall will now only support one leaf. WALLS: One of the first things you may notice when looking at the drawing above is that there are a lot of doors! The entrance on the south side will be double doors - there is already a solid core door in the existing wall. The two on the west side and the one on the north side are to allow natural light in from the windows when sound isolation is not needed. I intend these to be sized exactly to the windows (i.e. not going down to the floor). (Actually I may eliminate the one on the north wall - more on this later) The East side is storage space / computer closet - because the space is so skinny, one door won't allow adequate access, so I plan to put in two doors exactly opposite the window-doors. Each of these doors only penetrates a single leaf. I think that this may reduce the mass requirements relative to the ultra massive super-doors that are recommended when penetrating two leaves with a single door. My current plan is for walls with 2 layers of 5/8ths sheetrock with Green Glue. FLOOR: I plan to have the concrete floor polished ASAP. This will happen before any wall framing is done so they don't have to polish to an edge which is a big time/money saver (the framing will conceal the unpolished edges). This will be the full diamond honing process with concrete densifier and dye. This will not require any urethane or other top coat and is considered one of the most durable floor surfaces available. CEILING: This will be a completely independent ceiling on 2x6 joists with 2 layers of 5/8ths sheetrock and GG. because of the relatively long span (~ 14' 2") for 2x6s I will need to use select grade Douglas fir which is pretty pricey, but this will allow me to leave the existing HVAC ductwork on the ceiling in place and build the new ceiling completely below that (see second photo above). I will follow on with specific questions and to keep you all apprised of my progress. I look forward to any comments/criticisms/suggestions you may have. Thanks!

With a fully independent ceiling how does one attach the ceiling joists to the top plates of the walls? On one side I have enough room to nail a 2x8 to the ends of the joists and also to the outside of the top plate. Is that appropriate? How about on the other side where there is no room to do that - is toe-nailing the joists to the top plate enough? I saw reference on the web to using upside down joist hangers in this situation - is that recommended practice? See http://tedwhite.homestead.com/files/floating_joist_close_up.jpg

Dolphran wrote:

is that recommended practice? See http://tedwhite.homestead.com/files/floating_joist_close_up.jpg

No it isn't. But these are glu-lams in the picture and not joists like a 2X8, specifically. Look into Lilliths build here : viewtopic.php?f=2&t=11316&start=45 The actual picture is of MadMax's build over @ recording.org...but the practice is the same for anyone attempting this.

Is this what you are pointing me to in the Lilith thread? It's a very long thread and I couldn't find anything else relevant. It seems similar to what I had shown above. I won't have room to nail on the back side on one bearing wall, so any bracket would have to be on top of the (double) top plate or on the inside where it would be under sheetrock. Is that a problem?

I think Brien was referring to this one, specifically, but the rest of the thread around that area also seems relevant, to me viewtopic.php?f=2&t=11316&start=53 - Stuart -

Thanks for your response. My problem is that on one side I'll have no room to nail a banding board in from the back side. Is some kind of bracket appropriate then?

Thing is, the brackets are more for environmental impact and what you want to do is close the holes. So it may require blocks in-between the joists...but pictures of what you are doing help others to make sense of what we are talking about. Brien

Let me try again, I think my question is simple, but my description was poor. I building a completely independent (free standing) room in a room. My question is about the framing stage of construction - before any drywall goes up, but perhaps I should state that all drywall will all be on the inside of the inner room (NOT inside-out construction). Walls of the inner room will be very close to walls of the existing outer room. After framing the inner walls (2x4 studs, double top plate) I will then set the ceiling joists on the inner walls and will need to attach the joists to the supporting walls' top plates. The problem is I won't be able to get at the outside of the joists because the outer wall is in the way, so any attachment I do must be done from inside the inner room. I can toe-nail the joists to the top plate but I don't know if this is sufficient. The picture I referenced above showed using a hanger or bracket of some kind to aid the mechanical attachment of the joist to the top plate. I'm hoping to get other opinions of how to do this with the important consideration that I won't be able to get between the inner and outer wall to nail anything from the outside. I hope this is clearer, if not, I will attempt to create something in Sketchup that my help illustrate the issue. (Unfortunately I'm still a Sketchup novice) Thanks for your time!

"The problem is I won't be able to get at the outside of the joists because the outer wall is in the way, so any attachment I do must be done from inside the inner room." I understand since this is something that everyone doing this kind of build has to endure, but at the end of the day you have to do what will make the most effective hold on the joist so if that means using brackets like you are leaning towards, then do that, or if toe-nailing the joists can get the joist attached then you can do that, or a combination of the two. Joists brackets add additional cost and while they can make a good bond, it isn't a requirement for what you are doing, all things considered. A typical ceiling joist on a typical ceiling will be toe-nailed into the top plate...there really isn't any other way around it. Good luck, Brien

Thank you Brien, that was very helpful.

Oy vey HVAC! This is the aspect of my project I am least comfortable with. As I live in New England I have to worry about both heating and cooling, and also, of course, ventilation given the air tight nature of studio construction. Currently my house has forced air cooling and heating - two zones, main level and upstairs. Ductwork going to the main level is on the existing ceiling above what will be the new inner ceiling for the studio. If I run ducts from the existing house system into the studio for heating and cooling, I will be opening an air path directly to the upstairs which is the area I want the most sound isolation from. However, I will only occasionally need high sound isolation (maybe 10-20 percent of the time). I am thinking that perhaps I could tap into the home system but use sound isolating access panels on the duct openings into the studio so that I could fully close off the ducts when I need the isolation. Perhaps something like this - one for the air in, and one for the return. If I do that, however, then when I seal the ducts for sound isolation I will have no source of fresh air - that doesn't sound good. So I think I will need separate access to fresh air that doesn't directly connect to the upstairs when the studio is otherwise all sealed up. I wonder if simply passing a (long, serpentine) duct to the large (> 6000 cubic feet) basement room next to the studio would be a reasonable solution? This has the advantage of not being outside air at unpleasant temperatures, and I don't need great sound isolation to the rest of the basement, only to the upstairs. What do you think?

Is there any reason why you don't want to use the usual solutions, such as in-line silencers, long duct runs, lined ducts, and multiple 90° bends? Alternatively, if you really don't want any connection at all to the house system, then why not used mini-split air conditioners in the rooms, and independent fresh air ducts? - Stuart -

Soundman2020 wrote:

Is there any reason why you don't want to use the usual solutions, such as in-line silencers, long duct runs, lined ducts, and multiple 90° bends?

No reason at all! I'm trying to understand their appropriate usage/limitations in my specific situation. When I said "long, serpentine" duct I was alluding to long duct runs, lined ducts, and multiple 90° bends. But I was concerned that the connection to the upstairs system would perhaps still be a big problem even with those things, so maybe I should just use them in a connection to the adjoining room to provide a supply of fresh air. I could vent from out doors (where I don't have a big isolation issue) but without a heat exchanger (ERV/HRV?) I don't know if that's a good idea in my climate. My ignorance is vast and HVAC is currently well outside my DIY comfort zone. I'm trying to understand what I can expect from various solutions. I don't have a lot of time or money to dedicate to this, but I don't want to paint myself into a corner.

Soundman2020 wrote:

Alternatively, if you really don't want any connection at all to the house system, then why not used mini-split air conditioners in the rooms, and independent fresh air ducts?

I'm guessing that cost the and complexity of that kind of solution puts it out of reach for me right now. I am concerned however that this may be the only really effective solution and at the very least I think I would need to do my build in such a way that would allow upgrading to that kind of system in the future. Is that viable?

OK I have the outlines of an HVAC plan. To help make my plans clear I will show the studio in the context of the entire basement: In the summer the basement room adjoining the studio stays cool and that room's humidity is controlled with a dehumidifier set to 40% RH. This could be augmented with a window air conditioner if necessary. (It's a walk-out basement so there is a window in the west wall of that room.) I'm looking at this as my exchange room for the studio. I.e. having intake and exhaust ducts with fans connecting the studio with this room; perhaps with duct silencers in-line in both paths. Since the studio itself also has windows (albeit with isolation doors in front of them in the inner room) I won't need to pipe fresh air in directly from the outside for code. When the studio is sealed up, the exchange room will be my source of fresh, cool, and dehumidified air. In winter, the exchange room is not currently heated so it can get fairly chilly in there (but not as cold as one might think for an unheated room). I will definitely need heat in the studio to keep it at a comfortable office temperature (it will be where I work all day). I currently thinking that a 1000-1500w heater may be sufficient, but I don't have the numbers to back this up, especially in light of the air exchange with the currently unheated room. I think it will be prudent to run a 220 VAC line to the studio to support whatever electric baseboard I may want. In the worst case, if the studio is not warm enough I could connect the house HVAC system into the exchange room to bring it up to a more reasonable temp when necessary. This would be a fix that could be done after the studio is completed as it won't directly affect my build at all.

Oh crap, I've just started working through some numbers and the results are a little shocking. Starting with the equation BTU/hr = cfm * 1.08 * (Tin - Tout), I am trying to understand the cfm needed to cool my studio room from an exchange room. My studio room does not have a fixed calculable heat load. I expect the equipment in it could vary greatly over time, and the number of people will range from 1 to 5. Using the examples from Rod's book as a reasonable approximation I will assume a worst case heat load of about 12000 BTU/hr (1 ton). That would be with 5 people jamming in the room. Let's start with the recommended fresh air rate for five people of 75 cfm. That yields a temperature differential of 148 degrees Fahrenheit!!! I understand this to mean that the exchange room would have to be 148 degrees colder than the studio to keep the studio at a constant temperature at that air flow! If I up the airflow by a factor of 5 (375 cfm) that still means I need the exchange room to be 30 degrees colder than the studio and suddenly I'm talking big loud fans. Is this right!?

OK I've learned that the equation above only applies to sensible loads, and the 12,000 BTUH heat load I was referencing from Rod's book includes a significant latent load from the five people. It's also true that my equipment load is likely to be significantly less than the 1550 watts in that example. However, the calculation above is still quite eye opening. I see now that a mini split will likely be the only reasonable way to go. I'm considering the "Mitsubishi Mr. Slim 9,000 BTU 21 SEER Heat Pump Single Zone Ductless Mini Split Air Conditioner". From what I've read here these units are well respected. Any comments on using it in this room? Of course the mini split won't do anything for fresh air. I'm still a little torn on what to do there. Since my room has windows I believe I can skirt code and not have to get air directly from outside even though my windows have doors in front of them that can be sealed. If I pipe "fresh" air to/from the adjoining space I won't have to worry about the temperature and humidity of the exchange air. However I like the idea of getting true fresh outdoor air into the space. I'm 25 miles west of Boston, and our humidity in the summer can be really high (this year has been awful) so I like the idea of an ERV that can remove a great deal of humidity from the air on its way in. However Massachusetts winters can also get mighty cold and I am concerned that the ERV may not take well to strings of days in the teens or colder. HRVs are recommended for colder climates, but they don't do as much for the high humidity in the summer. I understand ERVs also require a condensation drain hose and I'm not at all sure how I would run that. Any thoughts or suggestions on this would be greatly appreciated. Thanks!

Rereading my own post above I think I make a compelling argument to run my 75 cfm air exchange with the adjoining room. If at some point I would like to upgrade the air quality I could always bring more outside air into the adjoining room, or even put an HRV/ERV in that space ducted between the outside and my studio ducts. Knowing these options exist allows me to defer worrying about it further until the studio is completed. So for now its going to be just about designing the duct connection to the adjoining room. I must figure out how the ductwork will run, its size, how I will build silencers to fit, where the fan will go, etc. Stay tuned, I will try to float some ideas here with sketchup.

I'm working on the design of ventilation ducting for the studio room. What I know: 1. This is to provide maximum 75 cfm exchange air only. (Heating/cooling will be done with a ductless mini split.) 2. This ductwork will penetrate into the adjoining room. The adjoining room has an unfinished ceiling, so I can easily hang ducts and the required fan in there. I will want to run fan speed control wiring back into the studio. I plan on getting a Fantech FR xxx fan that will give me at least 75 cfm with the static pressure my design ends up with. 3. Where the ducts will enter the studio is in the storage/server closet which is between my two leaves. What I think I know: 1. I want to use JM SuperDuct RC for the penetrations to the adjoining room because it is square and rigid an therefore relatively ease to caulk. 2. I want to use insulated flexible duct for some of the runs because its easier than trying to fab everything from SuperDuct. 3. My intake and exhaust grills should be on opposite sides of my room. What I don't know: 1. If I have at least three 90 degree angles in the SuperDuct, do I still need duct silencers? 2. Are commercial duct silencers (like this) as good as the DIY ones people make here? 3. How many grills do I need for intake and exhaust? Is two 8 inch each sufficient? Same size for Intake and exhaust? 4. Is "acoustical duct" like this recommended? Here's a Sketchup of the duct penetrations to the adjoining room. Thanks!