Modifying (cheapifying) - inside out wall

Due to several factors not least of which is city codes hassles - I have several walls framed up with no insulation against the block wall before studs and no drywall on the outside of framing (i.e. against the block wall). With a wall framed as such does it even make sense to use mineral wool, cloth cover, and slots to create a more absorbing wall or is this just money thrown down the rabbit hole? Will this wall be reflective regardless of wool and slots due to block wall behind framing. Should I just finish with drywall and call it a day? I can add treatments down the line. Object here is absorption on the back wall of a small 10 ft x 12 ft (and getting smaller) mixing room in a low ceiling basement. I don't consider isolation the priority since it is (hollow) block wall with no adjacent living space on that side.

Inside out walls are firstly for isolation, but it sounds like you are trying to do treatment. Which is it?

I have several walls framed up with no insulation against the block wall before studs and no drywall on the outside of framing (i.e. against the block wall).

In other words, all you have is stud framing, and nothing else? So you have the block wall, a gap, then the 2x4 framing, and now you would like to know what to do next in order to isolate and/or treat the room? Is that it?

Object here is absorption on the back wall of a small 10 ft x 12 ft (and getting smaller) mixing room in a low ceiling basement. I don't consider isolation the priority since it is (hollow) block wall with no adjacent living space on that side.

What about the other five sides? Sound expands in a sphere. Low frequency sound is not directional. Sound waves are not affected by objects that are smaller than their own wavelength. Therefore, sound that gets out through any of the other five sides of the room will simply wrap around the one good wall as though it did not even exist. In order to isolate a room, you have to do all six sides to the same level, including doors and windows (if any), as well as the HVAC system and electrical system. Maybe if you could post some photos of what you have, as well as an accurate SketchUp model, and describe what you are trying to do, then we'd be able to help a bit better. - Stuart -

Thanks for the reply - been trying to learn sketch up but, not sure if I have the time to invest in learning new software. Basically I have as you described - 2x4 framing about an inch from the block wall in basement. The space is somewhat oddly shaped with low ceilings and lots of drains, plumbing, ducting and bean to soffit around. Basically a square area with a square chunk taken out. Not a great space to build off and thus I am leery of investing to much into it when the starting point is weak. Just trying to get stuff out of a bedroom covered in eggshells and rug on walls. Basically a sidebar to renovating a bathroom and some other parts of the place. the plan is for a mix room/control room and a vocal booth with a pair of sliding glass doors between. The back walls (opposite where the sliding glass door will be) are framed up. The rest is undone. I was thinking of finishing the back wall with mineral wool, cloth and slots. but as I said - with out drywall behind not sure if it would all be for nothing. I will see about getting some better sketches posted and some photos.

OK - so spent some time getting to know Sketch up. Excuse my lack of sketch up skills in the updated attached sketch - it is not completely to scale but close. Several changes - I think I will have the entire basement area sprayed with closed cell foam insulation. My concern is future water damage and while we took quite a few measures already (gutters, reworked exterior sidewalks, sealant interior block wall) I am not convinced a good raining season won't cause problems. In the sketch I have indicated the spray foam as panels but - it is sprayed on. The walls that are already framed are the ones along the outer block wall. The studs are anywhere from 1/2" to several inches off the block. Spray will be applied right over framing (and electrical). Vocal booth layout (through the double sliding glass) - I plan on spending more effort and using the design posted here for the small booth as a guide. I also plan to attempt some "sound proofing" of the adjacent room as this will likely end up some type of "live sound" room with a drum kit. I will need to keep the noise in as much as possible (there is a another apartment in the building. Ceiling height and obstructions are a real problem. At this point - due to space and other issues (money?) not sure how much I can do in the tracking/mixing room. My understanding is that the closed cell sprayed foam is not much in the way of sound "absorbing". It will fill most of the stud wall cavity, eaving little room for much other treatment in the wall. Space is a real issue and really don't think another wall and framing can fit. The foam should seal up between and behind studs. Any suggestion before the hammer comes out again?

Updated sketch - getting the hang of S-U. This shows currently existing framing - along walls that will receive closed foam spray insulation. Second scene is proposed build out of framing - note the wall location between mix room and vocal booth will be adjusted - need to get there and make a few measurements. Was wondering about material choices - what sliding glass doors are people using? I have found some fairly cheap vinyl clad sliders made for exterior use. Are there better choices for interior sliding glass? The argon filed low e glass seems to get pretty dark when looking though two sets. I am considering just a commercial vinyl covering for the (cement) floor. Mainly do the head room issues. From what I have read on this forum, this is not a bad choice.

A couple of comments on your layout, Johnny: First, symmetry is critical. You need the control room to be perfectly symmetrical around you, at least from the front wall to half way back, meaning way past your head it still needs to be symmetrical. Your room is not. I would switch around the two rooms: put the vocal booth in that little area at the end (where you would be sitting in the current layout), and put the control room the other way around, with the back end where the vocal booth is now. Also, get your speakers off the desk! They will cause it to vibrate, and you will also have reflection issues like that. Either put the speakers on massive, solid stands behind the desk, or soffit-mount them (best option).

along walls that will receive closed foam spray insulation.

:shock: Why? That has no acoustic uses at all. Do you have a temperature problem in there, and need thermal insulation?

Was wondering about material choices - what sliding glass doors are people using?

Massive, heavy ones, with thick laminate glass in them, and excellent air-tight seals. They are not cheap...

I have found some fairly cheap vinyl clad sliders made for exterior use.

Probably not much use, acoustically.

The argon filed low e glass seems to get pretty dark when looking though two sets.

... and you don't want those anyway! Two sets of those would give you a four-leaf system! :shock: Lousy isolation. Not only that, the coincidence dips on all four panes would align perfectly.... :shock:

I am considering just a commercial vinyl covering for the (cement) floor. Mainly do the head room issues. From what I have read on this forum, this is not a bad choice.

That will work fine. Another good option is laminate flooring. - Stuart -

Thanks again for the help. Regarding the layout - I actually had it originally like you suggested. All the overhead beams, ducting and plumbing and such made me change it around. I will go back and look at it again. I am looking for ways to reroute some return ducts to get more room. Regarding the foam insulation and my original question - framing is up and while I am not required to put up more insulation things could get chili without it (Minnesota!). Also - while we added gutters , sloped walkways away from house and added plastic liners along the outside where possible and painted inside with block wall sealant - a basement is a basement and I expect a heavy rain may cause dampness. I understood the closed cell foam seals up along walls pretty good and adds R value as insulation. It seam like it would form a nice seal between the existing framing and block wall. I was considering doing that (two inches of spray foam along framed block wall) and then installing two inches of rock wool insulation, then covering with cloth, wood slots, etc - similar to the "inside out wall" only instead of 5/8" drywall I would have the spray. Once again I am trying to use existing framing, coat wall to seal it up somewhat and then maybe morph it into an inside out wall. I don't need to use the spray foam but, currently framing is just up along the block wall with nothing between. Just though some additional insulation and sealant might be a good idea. I have attached a cross section of the wall with foam for clarity. Regarding doors - any manufacturers recommended.? Not sure where to get heavy laminate sliding glass doors. I am guessing these are for indoor use - thus not to be found at the local building supply place. This may blow the budget wide open. Really speaking this may devolve into a a couple glorified closets with some treatment. Budget is really not there and I think not worth it for such low ceilings (85" max) and beams, poles, ducting everywhere. Just not a great space to start from. Might also consider putting electric heat under laminate/vinyl flooring. Wondering if anyone had EMI experience using this type heating? Thanks again Stuart. This website is fairly amazing. Reading through a lot of the posts makes me wonder how you and some of the others put up with repeating yourselves so much. PS - should this thread be moved to the studio design section? started with a question regarding construction.

I could do a layout something like this. Rough layout only - drop the sliders and use swing out doors. Still not symmetrical. There is a gas meter and small window in the one corner (sorry for no labels - have not quite figured out using the text tool yet). I drew a big 5ft window between booth and mix area. Could be smaller. I just don't see how to fit the desk and gear that makes sense.

Regarding the foam insulation and my original question - framing is up and while I am not required to put up more insulation things could get chili without it (Minnesota!).

Well, if you are going to isolate this room properly, then you'll be putting thick insulation inside the isolation wall anyway, so you don't need the foam. Plus, if you do it as in the diagram you posted, that would create a flanking path between the outer leaf and inner leaf, this "short circuiting" your isolation.

I understood the closed cell foam seals up along walls pretty good and adds R value as insulation.

You'll need to seal the walls anyway, but it's easier, cheaper and better to do it with simple concrete sealer, or even some types of paint. Brien is the expert in this area, but I suspect that by putting foam on the walls you might end up creating a situation that you don't want, regarding moisture and air movement. But he understands that stuff much better than I do, so maybe he can comment on that.

It seam like it would form a nice seal between the existing framing and block wall.

Bad idea! You do not want to join those two, mechanically! That would compromise your isolation.

I was considering doing that (two inches of spray foam along framed block wall) and then installing two inches of rock wool insulation, then covering with cloth, wood slots, etc - similar to the "inside out wall" only instead of 5/8" drywall I would have the spray.

That would work as acoustic TREATMENT, giving your slot wall the ability to work, but it would not work as ISOLATION: the entire room would be coupled to the outer-leaf wall. No isolation there...

Not sure where to get heavy laminate sliding glass doors. I am guessing these are for indoor use - thus not to be found at the local building supply place. This may blow the budget wide open.

Yup, they are expensive. Upwards of a thousand dollars each, and you need two of them. That's 2 k, just in doors. Not sure what your budget is, but that sounds like serious hole. :shock: Maybe a pair of ordinary solid-core doors would do the trick, much cheaper. You could cut holes in those and put glass in if you want, but another cheap solution for seeing into the other room is a simple camera-plus-LCD-monitor setup.

Budget is really not there and I think not worth it for such low ceilings (85" max) and beams, poles, ducting everywhere. Just not a great space to start from.

There are ways to optimize ceiling height, and 85" is low, but do-able. If that's the space you have, then that's what it is. You just have to be smart about making the most of it, and accepting the limitations. - Stuart -

You'll need to seal the walls anyway, but it's easier, cheaper and better to do it with simple concrete sealer, or even some types of paint. Brien is the expert in this area, but I suspect that by putting foam on the walls you might end up creating a situation that you don't want, regarding moisture and air movement. But he understands that stuff much better than I do, so maybe he can comment on that.

Water problems were not terrible originally - and we did a lot to mitigate through gutter, slop along walls etc. Actually painted the walls with the best sealant paint I could find too. Looks good at this point but, without a good rain who knows. How do I get Brien to comment?

How do I get Brien to comment?

You could PM him (xSpace) and ask him to look at your thread: He might not have seen it yet. - Stuart -

Johhny C, I have to ask you the same thing that we seem to have to ask for from anyone, we need pictures of these areas that are in question. Believe me, everyone that knows where they are and what they have does not mean that we can or even have the ability to figure these things out ...might even see something that you were not even addressing, it happens :) But let's see if we can cover some of the basics here. One of the main reasons a basement gets or stays wet is due to the walls being below ground level and subject to the moisture that the Earth contains, that's one reason. Another is the fact that the Earth is cooler and if the temperature/dew point is elevated above the exterior wall then you have a classic example of "warm to the cold side" path when temperature seeks equilibrium. So you have two paths that condensation and moisture can travel on built in to the basic basement, from the exterior and from the interior. Seems like a losing battle already doesn't it? :) The first line of defense is ALWAYS at the point of penetration, this means the exterior side of the structure. Not having any pictures of this to go on, I cannot point out immediate areas of concern but can still speculate, speculation is what we do often here :) Where ever there is a wall underneath ground, then that wall >should< have been prepared at the time of construction. This would include things like, asphalt based sealing and rubber or felt membranes on any part of the wall that is below ground elevation. The builder would also consider and install a French drain around, if not the entire perimeter, at least the areas of the basement that are below ground elevation. Does any of this seem likely to exist in your area? Anything above ground elevation would at least be properly sealed, maybe even painted. Concrete block is a very porous material and can and will soak up moisture until the point of saturation and move right inside. You cannot stop exterior moisture or water problems by approaching a level of attack from the interior side, it will not work, if the problem is related to cracks or poor exterior wall preparation, deteriorated wall sealing or the often as likely event that the ground elevation has gotten higher and is now covering the, what was, unprotected exterior wall. This is not uncommon especially after years of snow, water movement, owners modifying the grounds, flower beds being built up against the walls, etc., etc. But let's entertain the notion that maybe all these barriers on the exterior are in place and are working properly. You still do not want to place insulation up against the concrete/blocks since the >potential< for the dew point to change with the climate still makes that path a two way street, it can come in and it (moisture/condensation) can go out. So "warm side to the cold side" can change and does change. Now if we add insulation properly, to the newly framed wall assemblies as required by acoustic law, then you are going to make the interior side of the room the warm side...if not always, at least in large part. So while I understand you and people in your situation, wanting to ensure that you can be warm, you are going to be warm. And then you add electronic gear, human bodies and you will be warm mostly all the time, and that leads you to HVAC. The ability of a properly installed and sized unit will be able to even out the moisture in the room(s) so cannot be over-stressed. This brings us to the VDR or vapor barrier. when you frame wall assemblies in a basement, and this assumes the basement is more underground than not, you install the VB on the interior side of the framed wall assembly. Not that it (the VB) would go anywhere else in a cold region but it could be a case that you would not need one, but that would be determined by the actual wall assemblies that exist, the materials they are made of, etc. But, to be fair and in short, you have to address these issues from the exterior first because what you are going to do in the interior side is basically capture the ability of condensation to move, and take it out of the environment. Make sense?

I have to comment here, Brien: That's probably the clearest, easiest to understand explanation of the issue that I've seen! Even I understood it this time! Thanks! - Stuart -

This is an older structure in a downtown area - between buildings it is sloped away to a kind of drain channel where properties meet and further sloped to the street. French drain-ish. It is mainly cement walkways along the outside walls - these were rebuilt and sloped away from structure. Any wall without a walkway was built up with dirt sloped away from house and heavy plastic liners put down. The inside was sealed up with a high quality block wall paint sealant - I don't remember the brand. Debated drain tile and sump pump options but, was too big an undertaking. On the advice of several sources - I opted not to apply a vapor barrier (thick plastic liner along inside wall. This may not have been great advice but, there appears to be some real wide and varied opinions about the where and the how to apply the vapor barriers. And when applying spray foam insulation no plastic vapor barrier is used (this was the original plan). Here are some photos of the interior - things have progressed somewhat since these. I am looking to avoid tearing down any of this existing framing. Again - thanks a billion. I can shoot some additional photos this week of exterior.

"On the advice of several sources - I opted not to apply a vapor barrier (thick plastic liner along inside wall. This may not have been great advice but, there appears to be some real wide and varied opinions about the where and the how to apply the vapor barriers. And when applying spray foam insulation no plastic vapor barrier is used (this was the original plan)." Well, they are wide and varied, mostly incorrect coming from those that know about a one dimensional wall assembly but have never done a two dimension wall assembly...this is where we are at. In cold regions, the VDR (your VP) goes on the interior side of the living or heated environment directly attached to the studs. This is not up for negotiation, it is based on the principles of moisture diffusion, while very complicated for those that continue to study and up-date the phenomenon, there are standard considerations. Short answer is that in a climate with 8000 heating degree days (8000 / 72 degrees= 109 days of cold weather) the VDR is placed on the interior side of the room...no discussion. At 4000 heating degree days and depending on the materials that the wall was built from a VDR might not, and mostly will not be used...this would be close to where I live in Grand Bay, Alabama. As an aside, based on the perm rating of the materials I wouldn't think that my home that is only 27ish years old would have required one, a VDR that is. But it does, and it is on the interior side of the framing. We have about 3 or 4 weeks of cold weather, and this cold here isn't below freezing cold like you guys experience. So why does it work? It works because the HVAC helps in the process. Had it not had one, nothing would have changed really. The ability of the wall assembly to dry from interior to exterior or from exterior to the interior would have been made possible by the number of heated days (by the Sun) or the HVAC. So while they got it wrong, they still got it right. Now if we were in a tropical environment, the placement would be on the exterior of the framed assembly, often the VDR will come in the form of the actual finish, like say Stucco. But I guarantee you if you placed your VDR on the exterior side of the wall assembly in a cold region like where you are, it would not work, well, it would do what it is supposed to do, but the problem would be that the structure would suffer and rot, mold and decay would be the by product. But to place the VDR in the middle of a double wall assembly is asking for trouble. I have to go back to my soft drink can analogy to perform this next magic trick. Kid gets an aluminum can soft drink out of the refrigerator. Within seconds of being outside of the cold environment, the can starts to sweat. Now you think this sweat is part of the can don't you? It isn't, it is condensation in the air, the warm air to the cold side of the can. Now take that analogy and place it on the inside of the middle of a wall assembly full of insulation and what happens? The gas that is condensation when moving from the warm side to the cold side will "hit" the solid plastic sheeting, your vapor barrier in the form of closed cell thermal spray installed in between the walls, and stick to it. When the house starts trying to dry out, the moisture will migrate back into the interior framed wall, but before it makes it inside it has to go thru the insulation on this interior wall. And it cannot make it...it will diffuse on the insulation, wet the insulation and become a big problem and you will not know about it for months and months.

Yes - agreed - Been reading many articles about the VP and all seem to indicate the same ( except the ones that don't). Yet here I am, framed up - no barrier (see pictures). Framing off the wall by a 1" or so. I could sneak plastic up between I guess. Glue it, nail it, staple it, whatever. Best to adhere to the surface as tight and close as possible I believe. Many recommend pink (or blue) board glue solidly and thoroughly to the block wall surface. Too late for that I guess. Plus the NE Patriots lost so... Not real happy. But thanks for the continued support in this endeavor.

Just to open another can of worms - in the adjacent room I am trying to seal up for isolating purposes, previous owner installed standard fiberglass insulation and jammed sheet rock between joists. Pretty sloppy work but, I was originally thinking of just adding resilient channel across there joists and hanging sheet rock from that. Basically being lazy and not wanting to rip out all that sheet rock and insulation. Would leaving it up there create a problem?

Sir, when John Sayers has issue with my thinking, he brings it to me :) Here is the thing about what we do here in a nut shell. We each have varied interests, abilities and doubts about the projects we view. Stuart had some doubts about something in your build, he is a qualified acoustics technician...but we here do not limit our selves to this area...since we each understand that this has to be taken as a whole build in order for it to be a healthy build. No one here would no more allow you to install a 2X4 spanning 15 feet with 7.5 pounds of weight per square foot than they would allow a three leaf to go unmentioned or fire hazardous carpet to be placed on the walls. Does that mean it is acoustics to you...because it does not to me, it means watching a brothers back. Now you might think this is all acoustics, or voodoo in some nature, but I have to say this right before I walk out that door you opened for me. It is not. Not today. It may have used to been just like that but with every Tom Dick and Harry attempting to do what not only they often have no ability to do, but coupling that with the acoustic side that many also have no understanding of, those days are gone. If you would have asked me about the Patriots ability to get past Eli's NFL record ability to come back in the forth quarter I would have informed you that your money should not go on the Pats, who are a dieing dynasty beaten twice in four years by...the Giants. But you did ask about something I know much about. So I will tell you this. You do not get to hold me in PM or suggest that maybe I need to pay more attention to things that "matter", I know what matters ... everything matters. You still seem to be of the mind that you can install something that resembles a vapor barrier on the inside of this wall assembly and have it perform correctly, and to that I will tell you what I already have told you at length...it will produce an unhealthy environment, reduce your environment to rot and rust in short order...and this is information that few can or will give you for what you paid for it. We understand each other a little better now, I would hope, and you still have issues that you have not even addressed, but I cannot tolerate you telling me how I am supposed to perform my duties on this forum. Thank you for asking,

But you did ask about something I know much about. So I will tell you this. You do not get to hold me in PM or suggest that maybe I need to pay more attention to things that "matter", I know what matters ... everything matters. We understand each other a little better now, I would hope, and you still have issues that you have not even addressed, but I cannot tolerate you telling me how I am supposed to perform my duties on this forum.

I only PM'ed because I thought maybe the subject was not relevant to the forum and that you guys as moderators would not want long threads on subjects not really related to studio design so much as construction techniques. My bad I guess. Just so I am not mixing up what is meant by interior side of framing, etc. I went ahead and did a quick sketch of what I believe Brien is saying would be the best solution in my case. Edit - added channel to image. This is more or less what I am thinking along the block wall that are foundation. Would this be the proper way to install barrier and RC-8 type channel? My thought was to screw first sheetrock layer (5/8"), then glue the next (1/2") at different seams.

Attempting to get a decent layout finalized. With the space and windows/ obstructions I can't seem to find a happy solution for a symmetrical mixing area. Below is an attempt but, really lose a lot of space this way. The end users are looking to do a lot of "beat" creation and vocal recording for hip hop music. I believe they plan to spend lots of time in the mixing area together. It is just too small for two people like this. I will make a few more attempts but, my window for thinking this thing out is slowly closing (apogees for the over abundance of posting). Hammer, nails and caulk gun beckon. Please understand my deep appreciation for all the information on this website and the feedback. Even the advice about the NY Giants football team.

Is there any reason why you can't use more of the area? There seems to be a LOT of space around the area you are working in. Is there a reason why you are only looking at that specific area? The plan you have there in your latest post is unworkable: You might have symmetry, but the layout is not usable as a control room. Is it necessary to have the vocal booth so large? Could it be smaller? - Stuart -

Yes - this last attempt at symmetry doesn't do any good. If you mean why not in the adjacent area to the left of the I beam in the images - that is slated as a bedroom. IF you mean the area further to the bottom of the images (right of I beam) - starts getting into drains and mechanical area. The vocal booth does not need to be nearly as big. Note that I am looking to avoid soffits around I beam and HVAC ducting by placing the double walls far apart (1.5 feet) - seems smarter than all that ugly soffit drops and box framing, however, it does take away space.I am also attempting to re route some cold air return lines to create more space. The more I look at things the more I think the left side of the I beam needs to be utilized. This is the nuclear option in that at this rental property we are adding a bedroom and a bathroom to increase rent. Studio idea was an afterthought by tenant/building manager who has a big bedroom upstairs jammed full of stuff. Using full space - something like this is possible (first crack at it). Makes for a much nicer set up by far. Edit - added a more detailed layout - The desk is set up facing a window. That window was recently install (to comply as an egress window) and is fairly standard duel pane window. Don't really think I can add an inner window as this needs to be an accessible fire escape window.

How about if you put the bedroom in the area where you were originally planning the studio, to the right of the beam, and do all of the studio to the left (including the booth)? The bedroom will be a bit smaller, but still usable, and the studio will fit much better on the other side. I'd put the vocal booth at the far end, and then the CR. I think it makes more sense like that. - Stuart -

I don't think the right of the beam will work as a bedroom. For one thing it won't be legal without an egress window access. I suppose someone could always throw a cot in where I drew the drums and no one would know. I was going to have a hard time maintaining the code required 7 feet ceiling once I started adding resilient type channel or any extra layers of sheet rock anyway. I have only got 85" at most spots. I guess I will need to make a decision. I am thinking it will be best to just turn the whole thing into studio space but, try to maintain some resemblance of a normal bedroom shape. So that later it can converted back to living space with out a complete teardown. You seem to be saying split the bigger area left of the beam into a CR and a vocal room. Would this be preferred over as I have it layer out in this last one? (i.e. with vocal room and drum room right of beam and larger mix room left of the beam). I was sort of liking the layout with the desk facing the window. Just need to work out some angle details and proper placement of speaker soffits, etc. I really appreciate your help on this. This space has some issues but with some decent finish work it could be a pretty nice area.

Previous owners took out cross bridging, jammed fiberglass insulation and covered with drywall between the joists. I guess I know the answer already but, is there any way to minimize the effort here without creating problems? Can any of this be used as is? - Well guess I might as well tear it all out. I can start clean and do it as indicated in Mr. Gervals book = install some drywall against bottom of flooring between joists, caulk it up and secure with ledger board, re install bridging, add insulation and THEN install channel and sheet rock. (What is backer rod?) Unless someone sees a way to leave this all up there and magically achieve a decent result?