My first studio construction - appreciate your help

Splayed walls won't get rid of modal problems, it will only shift them to unknown variables :cry: The good news is, it WILL help things like flutter echo, and early reflections - it will also make modal problems (between the splayed walls, not between still-parallel ones) less violent in response, because the distance between those walls is constantly changing so the frequency will change as well. Be sure to thoroughly understand all the ramifications in that basement PDF before you finalize your plans - dunno about you, but tearing out walls and redoing them isn't on my list of favored things to do over and over and over - it's a short list, consisting of pizza, sex, beer, music, reading whodunnits, and...... nope, no wall-tearing out, sorry... :? Steve

I plan on using the design on p13, fig15 of the BSC pdf. So I would put 2" XPS board aginst the cement wall, then put in 1" 703 then 1 layer of 1/2" sheetrock. I'll have to use 1" 703 instead of 2-3" so that I can fit it in the stud cavity and leave a slight gap before the sheetrock. I think if I went with 2" I'd be stuffing it in there too much? I know slight damping has some benefits, but this seems like it may be too much? The only question is 703 a semi-permeable vapor barrier? (My limited understanding)The XPS insulation will allow some moisture through and allowing it to vent to the room. Because you want moisture to escape either to the outside or the inside, and I'm almost totally below ground so I need it to escape into tthe room. If the 703 is not permeable, then I would only be able to cover 1/2 to 3/4 of the wall height with the 703, leaving some are for vapor to escape. Don't know what effect that would have on my bass trapping, but it can't be good. So is this what you would derive from that pdf as well, or am I looking at it wrong? From the Owens Corning 700 pdf it appears that the 703 will not act as a vapor barrier (desired) unless faced with FRK. Which menas I should be able to cover the enitre height of the wall. I think I'll start a new thread on interpeting results of those calculators. I used a few and still couldn't tell what I was looking at. Didn't seem like I had any modal problems below 250 khz. Wouldn't that be lucky. But are you suggesting that with splayed walls modal problems will exist, but calculating them would be impossible? Thanks Steve! -HB

From the Owens Corning 700 pdf it appears that the 703 will not act as a vapor barrier (desired) unless faced with FRK

Yes. Plain (unfaced) 703 will let moisture through it. There's two types of faced 703, one of which is the FRK. I'm not sure how much of a vapor barier it is though. I think FRK is Kraft, which is mostly paper, so it's more of a vapor retarder than a barier. But I don't know.

Thanks for the confirm z. Everything I know about construction I learned here in the last 6 months, so no practical experience whatsoever. So making decisions that can impact the structure or performance of my new house is nerve racking.

Should have seen my nerves when I pulled that load bearing post out of the basement... :shock: :? Replaced it w/ a steel beam. So far so good, but it still makes me nervous...It's been nearly a year now. Aaron

I guess its safe to say thats a decision you should weigh carefully :D

My step dad does architect/engineer type work, so he did all the calculations of what I needed for the load. So far, so good... :D As far as the studio drawings, I did this all myself in autocad. With the great advice from everyone here on the site as to designs and angles, etc. :D :D :wink: Aaron

Which mode calculators are you using, and what are your room dimensions? Steve

Well its been a long time since I started my design, but construction has finally started! Thought I'd post my design and a few pictures. Plus I have a few questions of course! This room will be used mostly for post work like mixing/mastering. But also soundtrack creation as well. This is the last draft of my design. It's been changed a bit from this picture. I'm no longer doing double-walls between the studio and laundry. Also the closet is now a corner closet that is angled. Hoping to get a bass trap effect from this. This picture shows the entrance to the studio from the laundry room (elegant huh?) Here is shot from the rear to the front of the room. This shows the back closet, from the front wall. And just to round it out a shot from the right wall back to the door(left wall). Framing is now complete. Next is running electric, then HVAC. I have a question about soffits though. I'll be installing 2 30 degree soffit walls. Should I put these up after I complete the outer shell of the room? In other words, will the walls be "finished" behind the speakers? Seems like I would finish the wall behind th soffits, because I need those walls and especially the ceiling in that area, for sound isolation. Whereas the soffit wall is not built for mass, but just as a plane to extend the speaker baffle. But then would this create a triple-leaf situation at these points in my room? Does it matter? Well let's keep it there for now. Thanks to all active members for the great advice and effort in this community.

Welcome back! 8) I'm pretty sure you want the back of your soffit walls to be finished for a number of reasons -- isolation being one of them... Plus, it's a firebreak. I'm curious about your framing. The doorways look rather unconventional -- I don't think they meet code. Plus, is that rubber underneath the soleplates? If so, what kind of rubber is it?

sharward wrote:

Welcome back! 8) I'm curious about your framing. The doorways look rather unconventional -- I don't think they meet code. Plus, is that rubber underneath the soleplates? If so, what kind of rubber is it?

What looks wrong with the door? I had a contractor help do the framing for me, so I would assume it is standard construction. I floated the wall on neoprene. I didn't want to use small pucks, just wanted to have a consistent layer along the bottom, therefore no gaps to plug. So I used a softer neoprene, 40 durometer. You'll notice it I also used it along connection points with the joists and connecting walls. Only the wall between the laundry room and the studio is new(and the closet). 3 walls were already framed when I bought the house. They are all exterior walls(against the foundation). Since I couldn't float the existing walls, I'll be using RSIC clips with furring channel on all walls to attach sheetrock (2 layers 5/8" walls and ceiling).

Hashbrown wrote:

What looks wrong with the door? I had a contractor help do the framing for me, so I would assume it is standard construction.

I don't see any cripple studs along the top of the door frame. See this page, FIG. 5.

I floated the wall on neoprene. I didn't want to use small pucks, just wanted to have a consistent layer along the bottom, therefore no gaps to plug. So I used a softer neoprene, 40 durometer. You'll notice it I also used it along connection points with the joists and connecting walls.

Did you calculate the overall weight of your finished walls relative to the amount of compression that the Neoprene will accept without being overloaded? Ideally you want to aim for about 10-15% compression in order to achieve the necessary amount of compression for the Neoprene to act as a spring, but not more than that for fear of overloading the rubber and causing it to "bottom out" or wear out prematurely.

For any solid core door (hopefully yours, if you want much isolation) I MUCH prefer a heavier framing method so things don't settle and shift once the door's in - see my sketch about halfway down this page for what I mean http://www.johnlsayers.com/phpBB2/viewt ... 2&start=15 HTH... Steve

Thanks for the framing tips guys. I checked out the links you've referenced, and I will beef up that door frame. I didn't explicitly calculate my wall weight. I saw some references to how to calculate the weight, but didn't find the psf ratings for the neoprene. Also most threads were for floating the floors. So I looked at the spacing people were coming up with for floors, figured my weight for the wall would be much more than the floor, so knew I would have to space the pucks closer. Then I wanted to do a consistent strip along the bottom, so I got a softer neoprene (40 duro). I can use the softer neoprene for other applications as well, like decoulign my speakers from the floor, etc, where softer neoprene would be more effective(not much weight involved). So it's somewhat a crap shoot, but most of what we do here is educated guessing anyhow, so I'm not too worried. It's just a personal studio. I'm balancing doing it perfect, with actually doing it!

You can't afford to crapshoot on stuff like this... :( Sorry. That's the doggone honest truth.

I have a listing for manufactured rubber that says 95 pounds per CUBIC foot - neoprene should be right in there. So 1/2" would come in at around 4 psf, etc... Steve

ok, I figured out my walls to be ~350 psf. 2 layers 5/8" drywall on both sides of the wall(one side mounted on channel). Does that seem in the ballpark? So now I'm not quite sure what to do with that number. Steve you said you guessed the neoprene at 4psf? That can't be it's max load can it? I know I want to hit around 15-25% of the neoprene's max load in order to get the desired spring effect, correct? I guess I'm not sure how to calculate how much neoprene I'd need for a 6.5 ft long wall? Thanks for any insight.

Sorry, I thought you needed the WEIGHT of neoprene, not the weight it can SUPPORT. Now, do you really mean 350 pounds per square foot of wall? Should be more on the order of 20... Steve

Yeah, I figured I'm expressing it incorrectly. I calculated the wall to be a little over 700lbs. The wall has a surface area of about 68 sq ft. Now what I was figuring was that all the weight of the wall rested on a area of the floor that is around 2 sq ft (76 inch long wall at 3 3/4" thick). So I was thinking that the weight of the wall against the floor(and the neoprene) would be something like 350lbs per sq ft. So looks like I'm wrong about that? Obviously I don't kwow a thing about physical engineering! Ok so is it as simple as total weight divided by sq ft? So 700/68 = 10.29 psf?

I'm getting a little lost in all the calculations... But here's how to figure it in a nutshell. Figure 2.3 pounds per square foot per layer of 5/8" sheet rock. If you're using 4 layers, you're looking at 9.2 pounds per square foot, plus the weight of the framing. I'm assuming your walls are not bearing any weight above them -- that no amount of pressure will be placed on your top plates. This would require that the tops of your walls actually be a wee bit below the ceiling joists. Just for fun, let's suppose that including framing, you have 20 linear feat of wall that weighs 1,600 pounds. That's 80 pounds per linear foot. It appears you're using 2x4 construction, which means your soleplates are 3 1/2" wide. One linear foot has a "footprint" of 12" x 3 1/2". Multiply 12 by 3.5 and you end up with 42. That's the number of square inches that your linear foot occupies on the floor. Your 80 pounds is sitting on 42 square inches. That's just less than 2 pounds per square inch. Imagine a tiny piece of your Neoprene rubber that's cut to 1" x 1" (by whatever thickness it is -- 1/2" maybe?). Now imagine putting a two pound weight on it. Do you think that Neoprene piece will compress 10-15%? No way. It would probably require 20 times that, maybe 30 or 40 times that. (I'm just guessing here. :roll:) So, clearly, your rubber is severely undercompressed. What's the big deal? An undercompressed elastomer doesn't bounce, and if it doesn't bounce, it may as well not be there. The reason elastomers are typically cut into "pucks" isn't so much to save material -- it's to decrease the surface area on the elastomer so as to increase the amount of weight per puck, so as to allow it to act as the spring it is meant to be. Back when I intended to float a floor on my project (I have since decided not to float), I paid a machine shop to test some 1/2" thick 60 durometer EPDM rubber. Here are the results. Learn from the tests I paid $300 for. Again, you cannot afford to crapshoot this part of your plan. Mess this up, and you could end up with a worse result than if you hadn't attempted to float anything at all. I welcome any corrections to my mathematics or logic... But whatever the case, you have to calculate the weights and you have to know how much your elastomer will compress. Oh, one more thing. Don't assume that if a 1" square of Neoprene can compress a certain amount under a certain weight that you can use simple multiplication to figure a larger piece with a proportional amount of weight to get the same amount of compression. That is not true. What makes Neoprene act as a spring is its ability to squish out on the sides. The larger the piece, the disportionately more weight it takes to compress by the same amount. This is due to the decreased ratio of edge surface area to top/bottom surface area. There is a technical term for this but I don't remember what it is. In other words, there is no "universal" compression test for Neoprene -- the compression rate depends on the size of the puck. Hope that helps... --Keith :mrgreen:

I do understand all the theory behind what we're doing here. You can see by when I joined that I've been reading and re-reading this stuff for quite awhile. I agree that possibly I'll have an issue using this softer neoprene along the whole bottom plate of the wall. The question is how far off am I, and how much should I actually use? I've done lots of searching on this forum, and this seems to be the point where things always just trail off, it's never really been answered. I'm hoping this can help many others who get stuck once you really get down to the details. Like you said, we need to get the calculations and not take guesses, but then you go on to say that there is no way to know the compression rate of the neoprene unless we know the size of the puck. And then the only way to really know is go get this test done on my particular durometer. Well besides yourself, I haven’t' heard of anyone on this board doing that, so how did everyone else figure out the spacing when floating their floors/walls? Seems to me everyone is guessing. Sorry, a little frustrated that I keep getting warned not to guess, without any info on how NOT to guess. Anyway I did calculate the weight of the wall. I'll compare to your example for clarity. The wall is about 735lbs, and about 6.3 linear feet. So let's say 116 lbs/ft, translates to 2.76 lbs/sq inch. Like you said, no way that's going to compress a 1x1" piece of durometer (we think). So to compare to your tests, you used a piece of neoprene that was 5.25 sq inches. And averaging 1st and 2nd dry results, I'm going to say you'd need about 500lbs to get you 10% compression, or around 95 lbs per sq inch. Well let's see if I can take a stab at this. So if the weight of my wall is 735 lbs, divide that by 95 lbs, it means I should only use 7.75 sq inches of neoprene along my 6.3 ft wall to get the right compression? Well that's at 60 duro, mine is 40 duro, considerably softer, but how much? If duro is a linear measurement, then it is 1.5X softer. So instead of 95lbs/sq inch, we'd need 63 lbs/sq inch to get our 10% compression. So at 40duro I'd need around 10 sq inches of neoprene along the whole wall plate in order to get proper compression. Ok, do those calculations and assumptions seem reasonable? I'm guessing I've got some errors in there somewhere. Here is another disconnect for me; throughout the forum you see folks floating floors on 50 duro neoprene under 2x4's. When you calculate the average load on that floor I can't imagine you'd ever get enough weight to compress those pucks, unless you used really tiny pucks spaced about 8 ft apart. And then you'd be more worried about the floor sagging that 1/2 inch between the pucks and touching the subfloor anyway. So does this technique really even hold up(uh, no pun intended)? I really do appreciate you taking time out of your own work to consider and respond to my posts!

I'm getting kinda lost here too; are you trying to float a single frame wall (RC one side) on neoprene, or is this a 2-framed wall? Part of the problem with what you're doing is lack of information - few suppliers even KNOW what their materials will do. EAR composites http://www.earsc.com/HOME/engineering/index.asp?SID=6 is one of the few. Also, I'm not physicist enough to guide you through the complex math required to figure out what a WALL will do when floated; this gets into SHEAR properties instead of relatively simple compression. From what little I know on this, it's much easier to make things WORSE instead of better. This will be the case if you choose a material/thickness that comes close to the resonance of the entire wall, so that your "floater" material actually AMPLIFIES wall movement instead of cushioning it. As to figuring weight for purposes of VERTICAL deflection, this also gets tricky when using a continuous piece of rubber; all commonly available materials like this will ONLY work when allowed to "squish out" - IOW, they're not constrained sideways. When you use a continuous strip, you constrain the "squish" in the longitudinal dimension, changing the performance/compression of the material. This is why I posted the method I did in the REFERENCE section for testing your OWN materials; this is the only way I know of you can actually get it right because the cross-sectional area of your pucks will SERIOUSLY affect the amount of compression per unit area, using the exact same material. Add to this the fact that you're using at least one wall that's only a single frame, and bedding walls in cushion material becomes an excercise in futility. Personally, I'd just bed your walls in either sill seal or 2 layers of 30# building felt for purposes of Thermal Break (concrete, moisture, condensation) and, where using separate frames for each leaf, use NO RC. For your single frame wall (between you and utilities) the RC will improve mid-high frequency perfomance, so will be important to help block most machine noise. It's not important acoustically which side of the wall the RC goes on, just don't "short it out" with wrong screw placement. (REFERENCE section, first thread) HTH... Steve

Hey Hashbrown, I feel your pain, brother. I wouldn't say that nobody does the math. Paul Woodlock surely did the math. But I agree, it is rare. A lot of people guess and crapshoot. And when they announce that's what they're doing, people like Steve and me will speak up. There are no easy answers when it comes to float vs. not float. I battled it for months myself, big time. Pretty much like Steve said -- floating is hard to do right, easy to do wrong, and doing it wrong is worse than not doing it at all. I appreciate that you "get it" in terms of knowing the general direction to go with your calculations. If something is "wrong," you generally know what direction to move in to make it "more right." The problem is, "more right" is only "slightly less wrong" and there is a very small margin of "actual rightness," and anything outside of "actual rightness" is "distinct wrongness." :roll: Bottom line, it's impossible to find that sweet spot without a clear map. Unfortunately, the universal map you're seeking doesn't exist -- it actually needs to be custom drawn. This is why I have no faith in the Auralex U-boats. Here's why. (I realize we're not talking about U-boats here, but the same principle applies.) --Keith :mrgreen:

Thanks for the consideration guys! Steve, I am creating a single-frame wall, rc on one side and floated on neoprene. My whole purpose for floating the wall was to de-couple from the floor. I could probably achieve much the same results from using the RC alone, but thought I would create less margin of error by employing both methods. I know I've read your thread on testing neoprene. Just searched for it recently and couldn't find it again. Must be buried somewhere in Aaron's monster thread? I should say that I'm not going to use RC but furring channel mounted with RSIC clips(Kinetics). Keith - Yeah I know Paul measures! That guy is intense! I started following his diary when it was still under 20 pages i think :) You know I spent 6 months compiling info that I learned here into a cheat sheet, and read about so many other people's mistakes, and then I blow it myself, argh! Well, I'm going to see how well I can salvage this, I think i might be able to get portions of the neoprene removed from under the wall. Fortunately this wall isn't my biggest concern, it's the ceiling. The living room is right upstairs, so I've really got to put the most effort there. I'll double-check that strategy with you guys later, but it's pretty straight ahead, same methods most are using around here. So I know my previous post is bit dense, but can you guys check to see if my calculations, or at least my appraoch to them is correct? I'd like to kow if I now have an understanding of this. Thanks.