Hello everyone.
I am a heavy "researcher" on these boards, and I have purchased Rod's book and read it. I am a professional audio post engineer in CT, and am in the process of building a new room for myself above a garage. I have been involved in a few studio builds before, and I studied basic acoustics in college.
I have been working on the project for a month or so now (after working on it for a month 4 years ago before running out of money) and I am at a critical point.
I am following the dual leaf wall system and I am using perpendicular wood furring strips 24" OC to attach homosote/green glue/5/8ths rock/green glue/5/8ths rock for the walls. Most all of the walls are exterior walls and I am in the woods so I am very lucky not to need a huge amount of isolation. However, I do want to be able to play music up there some day, and I also have some jobs that keep me up working until all hours.
My issue is this: I used the Homosote as the first layer for 3 reasons: extra iso from the structure to reduce flanking, to have the option of screwing treatment into my walls at any spot on the wall. It goes up quicker than a layer of rock, and makes subsequent layers go up quicker. Homosote is great for all this as long as you use a #10 screw.
There in lies the problem . The only size I could find was not ideal, but I went with it anyway. It is a 1.5 inch #10 screw. No prob right? Well wrong. I am finding that the contractor is screwing the first layer of 5/8 rock into places where it will touch the furring strips when it should not (it should ONLY attach to the homosote). To make matters worse, the screws are too short to get the second layer of 5/8ths to suck into the homosote. So now I need new screws for the second layer. Again, I can't find the right screw!
My question: how much do I worry about the screws flanking the 1st layer of rock to the strips? Should I be frantically un-screwing screws and find a shorter #10 course thread shreet rock screw (though I can't actually find one)? How much of an issue is the 1/4 of an inch the screw extends beyond the homosote? Are all those holes I'm creating a disaster?
Am I blowing it here big time? Or am I over-reacting?
Urgent wall construction issue/question
Originally posted at johnlsayers.com, topic 10258.
i dont think they are if your not to worried about isolation.
joey
Well, I didn't mean to make it sound like I am not worried, I am. That is why I have so many layers of rock and thousands of dollars worth of Green Glue.
If the screws hitting the furring strips will make a huge difference I will order new shorter screws, pull the other ones out, and re-screw the sheetrock in the places where I know it hit.
It really only hits strapping around doors and near the ceiling and floor.....about 15 percent of the screws, and it only bites into the furring strips a 1/4 inch
i wouldnt worry about it because you are only doing single leaf.
It is a dual leaf system
Mass: Rock/gg/homo AIR Insulation Homo/gg/rock/gg/rock
I'm worried about flanking with the floor, but I'm also worried that Homosote is not as good a material as wood to hold a #10 screw (as big as they are).
Anyone else have an opinion on this?
depending on space available for deeper wall construction, it might have been better to go with rubber isolation mounts and hat channel and maybe a layer of plywood, since the homasote is generally not a strong backing for heavy layers of gwb... as far as the screws contacting the furring, its probably much less of an issue than if the screws are directly in the studs.
First,
homasote is lousy for iso any way - so I wouldn't get too worried here -
AND- you aren't really gaining anything more (throughout this whole long convoluted install you are going through) than you would have had, if you just installed the homasote directly to the studs - and then the drywall to the studs as well.
NEXT - forget this whole screw idea you have - you cannot possibly get enough holding power (without fully penetrating the homasote) that you would have anywhere near a safe installation of the 2 layers of drywall with just the tips of screws holding your drywall to the homasote.
Lastly,
You said you have my book and read it - then why in the world did you think that you could install furring stripis and that they would perform to create any meaningful isolation from flanking?
I explain in the book how critical it is that you use real RC - because simple steel framing sections will not create isolation - example - hat section won't give you iso - although RC-2 will - and yet it has less cross sectional area in contact with the frame than the furring you installed.
Got it?
At this point in time - just make sure that you install screws sized long enough to fully engage the homosote - PLUS penetrate at least 3/4" beyond the back of the homosote to assure proper installation of the drywall - and count your blessings that you don't have any real issues with iso itself -
The green glue will help to compensate a lot for the remaining monies you invested that don't amount to anything much other than an expense with no benifit (no penalty either).
You should have asked a lot more questions before heading down this path...........
Sincerely,
Rod
Glenn, you surprise me - by rubber iso mounts do you actually mean RISC clips and hat section? Be very carefull how you present things here - it is becoming more and more my experience that unless we are very exacting as to what we present - people are getting some very weird pictures in their minds. Roddepending on space available for deeper wall construction, it might have been better to go with rubber isolation mounts and hat channel and maybe a layer of plywood, since the homasote is generally not a strong backing for heavy layers of gwb... as far as the screws contacting the furring, its probably much less of an issue than if the screws are directly in the studs.
Rod,
thanks for the reply. Let me explain a few things here:
I knew that 1x furring strips were not going to do the same thing that RC channel was going to do. I only did it on one side of the wall. The only reason I did it on that one side is because:
A: it helped me insulate B: it kept my room symmetrical with the wall opposite it C: is was inexpensive and was easy to do for MY contractor.
Since you are a world class designer you probably don't have to make decisions based on what you think your builders can deal with. But in my situation I decided it was not worth dealing with. I can't be there during the day while the guys I have are building. I didn't trust them to use it correctly, and quickly.
Now, I am puzzled at how horizontal 1x strips 24" OC are not better for reducing flanking than screwing directly to 16" vertical studs attached to a plate. The area that the strips attach to the wall (and can transmit sound) is so much less than it would be otherwise. While I agree and believe you that what I did is not ideal, or what you would have prescribed, I have been told by other designers that I am consulting with that it is of benefit (furring strips and homosote) for how much it costs (material and labor). With all due respect sir, you are not the only designer whose material I read, or with whom I consulted. I mean no disrespect.
The strips were not a huge pain, there is not that many of them, I'm glad to have the homosote there because it was quicker to install than rock, and it gives me a nailer anywhere on the wall I want to build acoustic treatment (important in my case). For my situation using homosote has a benefit, at a moderate cost. However. I used 3/4 OSB on the ceiling instead of homosote for the very reasons you guys mention (about it's strength). If weight wasn't a concern I would have used it on the walls also. I'm wondering if that would not have been better now. Oh well. no point in regretting that one.
Now, I am really glad to hear your advice with the screws. Very interesting. I tried some longer screws that I special ordered today and they did not bite nearly as well as the shorter ones did ( the shorter ones I have are a different brand with a more aggressive thread). Do you really think it is unsafe to have screws NOT extend 3/4 through the homosote even with the green glue. If so I will order long #10 screws immediately. I don't understand the benefit of going past the tapered end of the screw?
One question: I have read that green glue is not an adhesive... but we have done a bunch of tests. I have some 5/8 rock hanging off a piece of ceiling in my garage with only green glue attaching it (a 2x2 piece). Do I really need to worry about going so far through the homosote when the pieces are also glued together with 2 tubes each of green glue?
Does GG have any adhesion properties?
First off - there are no definitive tests indicating that homosote has any value at all - just claims by the manufacturer. Now - that material has been around since before the days that my father was a builder - and I hadn't been born yet...... Is it possible that there has not been a single test performed in all that time - or is it more possible that they were performed - and the product isn't worth the investment? Which would explain why the manufacturer has never released any hard data. Ask your other designers for copies of the test results performed by the independant labs......... perhaps they have invested the monies to have the product tested......... All I can tell you is that anyone who would suggest to you that you invest an additional "X" dollars on construction (regardless of how little that extra investment was) without being able to tell you exactly what that extra cost would benefit you in isolation is someone I wouldn't want to be doing business with.........Now, I am puzzled at how horizontal 1x strips 24" OC are not better for reducing flanking than screwing directly to 16" vertical studs attached to a plate. The area that the strips attach to the wall (and can transmit sound) is so much less than it would be otherwise. While I agree and believe you that what I did is not ideal, or what you would have prescribed, I have been told by other designers that I am consulting with that it is of benefit (furring strips and homosote) for how much it costs (material and labor).
None taken........With all due respect sir, you are not the only designer whose material I read, or with whom I consulted. I mean no disrespect.
Frankly - as I said - the homosote is a waste - if you can't trust it on your ceiling - what makes you think it is any better a structural element for hanging heavy objects just because you put it on a wall........ Also - are you telling me that the other designers told you thast the OSB on your ceiling would be equivilent in isolation as the homasote on your wall? Homasote is a very soft material - it is not intended for hanging heavy objects - eventualy the screws work loose........... just the same as they do in drywall........The strips were not a huge pain, there is not that many of them, I'm glad to have the homosote there because it was quicker to install than rock, and it gives me a nailer anywhere on the wall I want to build acoustic treatment (important in my case). For my situation using homosote has a benefit, at a moderate cost. However. I used 3/4 OSB on the ceiling instead of homosote for the very reasons you guys mention (about it's strength). If weight wasn't a concern I would have used it on the walls also. I'm wondering if that would not have been better now. Oh well. no point in regretting that one.
Your screws don't suck up tight because the homasote is a lousy structural material (I keep pointing that out to you - and the homasote is pointing it out as well) I'll bet those screws would suck up just fine going into a structural stud. The building codes are minimum standards....... and the smallest screw you can use for installing 1/2 drywall by code is 1 1/4 - that is 1 1/2 times the board thickness beyond the board - into a structural board.......... which the homosote isn't. To me the benefit is peace of mind. Probably doesn't matter so much on a wall - definately on a ceiling......... when you step up your next full screw size - that will automatically put you past the tapered end (if your last screw was just beyond flush to the back face - which was how you described your situation.) - you'll wind up somewhere around 1/2 to 3/4".Now, I am really glad to hear your advice with the screws. Very interesting. I tried some longer screws that I special ordered today and they did not bite nearly as well as the shorter ones did ( the shorter ones I have are a different brand with a more aggressive thread). Do you really think it is unsafe to have screws NOT extend 3/4 through the homosote even with the green glue. If so I will order long #10 screws immediately. I don't understand the benefit of going past the tapered end of the screw?
Green glue is very sticky - but it apparently never cures - it stays just that sticky - which is why it works........ I could not even begin to guess long term how it would react to loading - but I can picture all of it's little fissures that develope in it as it does it's job - opening up a little more over time as it carries a weight it was not designed to carry.......... I wouldn't chance it......... BTW - I am not trying to be disrespectfull of you either - am just dissapointed to find out that they are still designers out there convincing people to throw away their money on crap construction that they themselve can not possibly put real values against. Personally - if you really had to take this route due to room (or financial) constraints (versus a room in a room) - my advice to you would have been to forget the furring - install osb - GG - 5/8" DW - GG - 5/8" DW - and then be carefull not to bump the wall - impact noise would have been your lbiggest enemy....... still is. RodOne question: I have read that green glue is not an adhesive... but we have done a bunch of tests. I have some 5/8 rock hanging off a piece of ceiling in my garage with only green glue attaching it (a 2x2 piece). Do I really need to worry about going so far through the homosote when the pieces are also glued together with 2 tubes each of green glue? Does GG have any adhesion properties?
Rod,
Thanks so much for the advice, I'm going to forward this response to a few people.
I agree that not a single lab test since 1909 is suspicious, especially since they tout their product as a sound deadening product with isolation properties. OSB would have been better if my structure could have handled it (probably could have). I have worked in a bunch of studios with rock/homo/rock walls and isolation was good. This is why I didn't balk at the suggestion.
I'm confused. The green glue site has tests, and says that green glue works very well with generic sound board (not as dense as homosote 440). They conclude that it is not worth using instead of Sheet Rock because you lose mass. However, it does work as mass in a Green Glue wall setup (tests are on their site). So, are you saying the extra money was a waste? Or are you implying it does not do anything to stop sound over there being nothing there? I still don't see it at as a total loss. The screws I tried the second time were not only too short also (only 1 3/4 inches) but they didn't have threads on the top 1/2 inch of the screw!!!. I purchased them on the web (sight unseen), and they were billed as sheetrock screws. What kind of sheetrock screw has no threads on the top 1/2 inch? I'm going to fight with the people that sold them to me. I now have 1000 useless screws. Also, I couldn't sleep last night so I was up there with every screw I could find in my shop. As it turns out you were right about the length. Even a #6 2 1/2 screw bites fine. What is impressive is I tried to pull it out with all my might and pair of plyers (I'm only 165...not exactly hulk Hogan) and I could not. The Homosote will still work for me as a nailer, and as my builder did point out yesterday, my structural side walls are only 2x4 walls!!!! That layer of OSB I could have used would have been hard to pull off since we are approaching some weight issues. Beefing up those walls in the 1st floor section of this studio might be in order regardless. What happened was this structure was only designed as a garage with a loft at first, and grew tall enough during construction to accomodate the space I needed for a future control room (yes it was inspected by the town building official). After labor, I estimate it cost me an extra $200-$300 on this project to have the homasote instead of sheet rock as the first layer on the walls. I gained a nailer, but lost mass. I thought I was gaining Iso over rock, but apparently I did not, not the end of the world. When the studio is finished I will test to the best of my ability the STC of the one wall in between my instrument rooms and the control room to see how well (not well) the wall system worked. This framing of the structure happened in 2003, 5 years ago, which is why we needed the OSB on the ceiling. Let me explain: The rafters and collar ties that the ceiling attaches to are 2x12 Doug Fir (rafters) 2x8 Doug Fir (collar ties). I have very beefy ridge lam, and a lam cross beam under the second floor. No cross members were attached to this lumber in the last 5 years, and the space was unheated. However, the space was insulated back at the time of construction. 4" of rigid poly-iso insulation was cut and force fit in between each and every rafter and collar tie. So, you can imagine what happened in 5 years. Those suckers twisted like mad, and I needed something very stiff to push up the insulation. Rock would not have sucked tight enough, and screws would have popped if any of the insulation dropped below the 1x furring strips and layed on the rock. Just to be clear, the poly-iso was NOT used because of it's sound properties. In fact. as many batts of r30 as I could fit up above the collar ties (and above the poly-iso were installed to deaden the ceiling cavity without affecting venting (also a reason to want something beefy up there. Also, I had the builders (in 2003) angle the collar ties 1ft up for every 10 ft of distance. Needless to say they were not as exact as I would have liked them to be. We used OSB because we needed something very stiff to both suck the insulation up.....keep it up....and also something we could shim down in spots. Without doing this my ceiling would have been wavy as hell. I'm mixing in this room at 85db day after day many times with clients. It needs to look as nice as it sounds, and it doesn't need rock band type isolation. The layer below the 3/4 OSB is GG then 5/8 rock. I think it will work well for what I need it to do.frankly - as I said - the homosote is a waste - if you can't trust it on your ceiling - what makes you think it is any better a structural element for hanging heavy objects just because you put it on a wall........
No one ever said that, see above.Also - are you telling me that the other designers told you thast the OSB on your ceiling would be equivilent in isolation as the homasote on your wall?
This is simply mis-leading. It is not in ANY stretch of the imagination soft. If you take a piece (I can send anyone here a sample) and try to push your finger into it it does NOT budge. If you try and take a corner and break it off it does NOT break (you can get it to bend a little). I took a hammer (estwing) held it over my head and banged on a piece this morning. I could only get it to dent maybe 1/16 of an inch (try that with sheet rock). You are probably correct, it is under-tested in the lab, and probably a waste for most people on this board, but this statement is misleading. If I had the time (and the know-how) I could post video of me trying to pull a screw out of the stuff with all my might and I can't do it, where I can do it with sheet rock with some ease. I respect your informed opinion on it's uselessness for isolation, but to say it is "soft" is a stretch. It would not be used as an external sheathing if it was soft. Maybe it is soft in comparison to plywood, but then I would say soft in comparison. Flexible, sure especially compared to OSB or ply wood. Saying it is soft gives someone the impression it dents easy. We had to replace our saw blades after cutting through the stuff for 2 days. We also had to pull a few pieces off that were tacked up with ring shank nails from a gun. We needed a crowbar to do it. Not as hard as OSB, but not soft. I have a lot of scrap if you want a piece. Rod, thanks for the invaluable advice about using longer screws, and not relying on the Green Glue for structural support . Your post will help me greatly explain to my builder how the green glue will NOT work over time as a structural adhesive. It is tough working with builders not used to the concepts of sound transmission (especially when I am in the studio or on set all day) I know where to get #10 2 1/2 screws and I will be getting those to insure my walls don't come apart over time. I'll let you know if they work better. 80% of the 1.5 inchers bit well, and 60% of the second layer is up with those, but I will be re-enforcing it before taping. The 1.75 inchers I used didn't have threads on the top (why they didn't bite). Also, I'm not going to shy away from hitting framing members on your advice. Sorry you think the construction is crap (I'm going to edit that part out for my builder), but thanks so much for the help. Your book is really is great and up to date, but there are still a few details in regard to your door designs and window designs I might need clarification on. Don't worry, for both of those we will be following your plans exactly :wink: Thanks again.Homasote is a very soft material - it is not intended for hanging heavy objects - eventualy the screws work loose........... just the same as they do in drywall........
Actually - I never said that - I said using homasote for iso-board with wood furring as a base - was a waste - as in waste of money. There is a reason that hat sections don't work the same as RC-2 - and that is because the slots (or holes depending on the manufacturer) help to disapate the passage of sound. You figure that even between resilient channel - it's easy to get 3dB difference in iso just based on the manufacturer - best being around 6dB of isolation compared to directly attached to the stud - with the worse being roughly 3 dB of added isolation Switch to Hat section and loose all of that - it's as if it didn't exist. You can't be getting your monies worth with the furring - it has greater cross sectional contact with the framing than hat section does to transmit noise through.......... And - although you do gain something from the homasote - it is not anywhere near that of substituting OSB or Drywall for the layer - (due to the loss in mass) and it's the mass that is so critical in these walls. It's the mass that gets us there with Low Frequency Tl - period. SO to look and say "well at least I got something for my money" - I SAY "The gain versus the investment does not make sense on the face of it. Heck - you can buy Quiet Rock and get great performance - but I still tell everyone not to waste their money on it - because the cost for performance can be beat out (in the end) by simply adding layers of gyp board. As far as backing board goes - me - I have this idea in my head that it is worth it to take into account everything you might want to hang on a wall - and then to place blocking in those locations to carry the load. I wouldn't back an entire wall just to save the think ahead and layout. Especially not when I can get better results (from an iso point of view) with drywall........ When I design a wall with structural sheathing as a base - it's for seismic reasons - wracking strength......... not so somone can hang things up, down the road. Sincerely, RodSorry you think the construction is crap (I'm going to edit that part out for my builder), but thanks so much for the help. Your book is really is great and up to date, but there are still a few details in regard to your door designs and window designs I might need clarification on. Don't worry, for both of those we will be following your plans exactly :wink: Thanks again.
Sorry, I thought that was directed at me and my designer (who helped for a labor swap with me).BTW - I am not trying to be disrespectfull of you either - am just dissapointed to find out that they are still designers out there convincing people to throw away their money on crap construction that they themselve can not possibly put real values against.
Fair enough. I understand where you are coming from now on all of this. I agree it would have been better to have planned out all of the acoustical treatments first. And yes, If I was a professional designer, or was paying a professional designer I would expect the same for sure. I only got design input on the wall layout and shape, not the treatment. I couldn't afford it. For me, this project is funny. I abandoned it 4 years ago, and then, all of a sudden I needed it done in 6 weeks without having thought about it for years. It looked like I would never be able to afford to build it, heat it, pay for the property taxes on it. So it sat, with a whole bunch of audio wiring, electrical wiring, angled framing and the such. Then one day everything changed for my family and for my business, and I had the opportunity to have 2 skilled construction workers building it at about half the going rate. I jumped on the opportunity and tried to plan the best I could with the short amount of time I had/have (never mind the screaming baby). I decided I did not have the vision to plan treatment before hand, and I want to build a lot of the bass traps and diffusion myself to compliment all of the Real Traps I have. So, I went for the backer board approach. Eh, what is done is done, I'm just glad I got your input about properly screwing the stuff in. My builder responds well to second opinions, and by showing him your previous post I can convince him it will be worth while. In retrospect I should have went out of my way to find RC channel for just that one wall, but I don't think it will kill me. Anything louder than a VO in those instrument rooms will be a hobby (I used to be a musician). My exterior walls just have to block out the sound of my neighbor's leaf blower, and my other neighbor's barking dog. I think I have done that! I can only hear those things through the window now. Thanks again!As far as backing board goes - me - I have this idea in my head that it is worth it to take into account everything you might want to hang on a wall - and then to place blocking in those locations to carry the load. I wouldn't back an entire wall just to save the think ahead and layout. Especially not when I can get better results (from an iso point of view) with drywall........ When I design a wall with structural sheathing as a base - it's for seismic reasons - wracking strength......... not so somone can hang things up, down the road.
yes, i meant RSIC (pacintl) clips and hat channel but they have different names depending on who makes them (like mason ind (FD), pacintl (RSIC), kinetics (IsoMax), etc) so rubber isolation mounts seem generic enough - like "rigid insulation" etc... and some of them use "furring channel" some use "hat channel", etc... thanks!you surprise me - by rubber iso mounts do you actually mean RISC clips and hat section?depending on space available for deeper wall construction, it might have been better to go with rubber isolation mounts and hat channel and maybe a layer of plywood, since the homasote is generally not a strong backing for heavy layers of gwb...
I posted this Looking for what homasote/sonopan/fibreboard actually does in wall construction. Note the counter-intuitive conclusion at the end of the thread about that material. This is just one example why experts like Rod are loath to suggest anything that is not lab tested, well within the known limits of extrapolation, or personally tested/experienced. Helpfully Andre. Is it possible that there has not been a single test performed in all that time - or is it more possible that they were performed - and the product isn't worth the investment? Which would explain why the manufacturer has never released any hard data. Ask your other designers for copies of the test results performed by the independant labs......... perhaps they have invested the monies to have the product tested.........
I could be mistaken - but I think that hat and furring are one and the same thing......... just different verbiage for different parts of the country. Like up here in the northeast states we call it "money..........." And the Cajuns (down south) call it "duckies"... But it spends the same. 8) Sincerely, Rodsome of them use "furring channel" some use "hat channel", etc...