do i have to moisten the fiberboard before i install it

hi - i am installing an extra layer of gypsum to give better isolation in my home studio - i have read ( think it was somewhere on this site ) that a layer of fiberboard between the 2 layers of gypsum can give better isolation - we dont use the term fiberboard here - looked it up on wikipedia and aparently high density fiberboard is called hardboard ( which we have ) - so i got some - it's a few mm thick and it's used to make the back of cheap bookcases and cd holders etc - i hope this is the right stuff ( if it isnt then i just wont install it ) my question is this - people have used this material for making ceilings here in the past and it expands and buckles so what they did was wet it before they installed it so that it shrinks when it dries and stays flat - what i need to know is: a - do people think i have the right material b - if it is necessary to wet it before installation c - what is the installation technique - my options are nail gun, glue(grip fill we call it), or screws - was thinking combination of glue and nail gun into the gypsum but not into the studs thanks for your help ps if i have missed something on the forum about this then apologies

bobmurphy wrote:

hi - i am installing an extra layer of gypsum to give better isolation in my home studio - i have read ( think it was somewhere on this site ) that a layer of fiberboard between the 2 layers of gypsum can give better isolation - we dont use the term fiberboard here - looked it up on wikipedia and aparently high density fiberboard is called hardboard ( which we have ) - so i got some - it's a few mm thick and it's used to make the back of cheap bookcases and cd holders etc - i hope this is the right stuff ( if it isnt then i just wont install it ) my question is this - people have used this material for making ceilings here in the past and it expands and buckles so what they did was wet it before they installed it so that it shrinks when it dries and stays flat - what i need to know is: a - do people think i have the right material b - if it is necessary to wet it before installation c - what is the installation technique - my options are nail gun, glue(grip fill we call it), or screws - was thinking combination of glue and nail gun into the gypsum but not into the studs thanks for your help ps if i have missed something on the forum about this then apologies

a - do people think i have the right material Sounds like you have soundboard. Some say it can be used to decouple, some say go with GreenGlue. I would go with Greenglue. b - if it is necessary to wet it before installation No you don't want to wet this. Really you don't want to wet any product unless it specifically says to do so on the label. You'll be inviting mold and i don't see how wetting fiberboard will do anything but ruin the product. c - what is the installation technique - my options are nail gun, glue(grip fill we call it), or screws - was thinking combination of glue and nail gun into the gypsum but not into the studs You need to check building codes to see how long of screws you need. If you do go with the soundboard in between the gypsum, you need to make sure your screws are penetrating long enough into the structure so that it doesnt pull out. Theres other threads here that have gone about the technique. D. Don't use Wikipedia for information..its dubious as it is user editable. Use tried and true construction and material practices. E. Whats your studio plan??

IF it's heavier/more dense then gypsum then yes, good choice. If it is soundboard lke n8nod9it said, then it's a bad choice... that is IF you had to buy it... but if it's FREE and you already own some then it will still add to isolation. Soundboard does not help in low end isolation ( referred to on forum as TL or Transmission Loss) as much as Gypsum but sound board will make a STC# improvement because STC does not really consider the low end, STC is meant for voice only.

c - what is the installation technique - my options are nail gun, glue(grip fill we call it), or screws - was thinking combination of glue and nail gun into the gypsum but not into the studs

That's a big NO, especially on ceiling. You want to attach any layer of wall covering to the studs... all gypsum, stuff you have and even house wrap such as Tyvek direction are to place fasteners through sheathing directly to studs.. house wrap is just paper. Marc

thanks guys for replying well i found the place that i originaly read about this for a start it's here http://www.saecollege.de/reference_material/index.html i have quoted it

adding to the layer can dramatically increase the transmission loss. The options are * Adding another layer of gypsum which is glued (not nailed) to the first sheet and should be a different thickness than the first sheet. i.e. 16mm (5/8") and 12mm (1/2") * sandwiching a layer of fibreboard between the two sheets. This really works well, a double wall with a triple layer as described above on a floating floor will create a room that will allow you to set up a band and not hear it outside the room! Just remember that all the sound is now trapped inside the room and heavy acoustic treatment is required to control it all.

n8nod9it not sure about soundboard - never heard it called that - i have attached a pic of what i have and also a pic of my studio plan - it's a bit like mdf but nearly as flexible as cardboard with a waxy coat on one side and a soft rough texture on the other the wall in question is to the right of the drawing guitardad72 - actually this stuff is just going on a wall, not a ceiling, what i was saying was that in REGULAR building here it HAS been used on ceiling joists instead of gypsum and if was put up dry then it would sag

That's a big NO, especially on ceiling. You want to attach any layer of wall covering to the studs... all gypsum, stuff you have and even house wrap such as Tyvek direction are to place fasteners through sheathing directly to studs.. house wrap is just paper.

.... however from the quote on the saecollege site above it says

* Adding another layer of gypsum which is glued (not nailed) to the first sheet

- now going by that then i should glue the second (and i suppose 3rd layers instead of nailing them )and this extra layer i have is very light also thanks again for your help

bobmurphy wrote:

n8nod9it not sure about soundboard - never heard it called that - i have attached a pic of what i have and also a pic of my studio plan - it's a bit like mdf but nearly as flexible as cardboard with a waxy coat on one side and a soft rough texture on the other the wall in question is to the right of the drawing

For the record, Bob, here in the States we call that stuff by the brand name "Masonite."

Bass Rocks wrote:

bobmurphy wrote:

n8nod9it not sure about soundboard - never heard it called that - i have attached a pic of what i have and also a pic of my studio plan - it's a bit like mdf but nearly as flexible as cardboard with a waxy coat on one side and a soft rough texture on the other the wall in question is to the right of the drawing

For the record, Bob, here in the States we call that stuff by the brand name "Masonite."

yip that looks like it, thanks

Yeah that is Masonite... I still wouldn't get water on it for any reason, its a compression fiber product and any water on it would likely swell it, or stay trapped in it, which you wouldn't want layered between gypsum. I don't know how effective that will be in TL isolation. I suppose if you had enough for free, it would be ok to use but it is very thin. Also, that SAE article mentioned gluing the layers together which IMO from what i've read, cause the coincidence frequency of two seperate pieces of material to be merged into one new larger coincidence freq, instead of two seperate frequencies. Two would be better than one, two with GG inbetween would be best. I was going to use MDF in my walls because i could get it for cheap, but i decided not too...Much too messy to cut and heavy. But you'll have to decide whether the Masonite is appropriate after considering its acoustic properties and worth.

Bob,

however from the quote on the saecollege site above it says

The SAE site is a great source written by John back in 1998. John no longer has any control of the web site. It's a great intro into the world of studio building, however even John admits part of the info is out of date. Newer research, tests and discussions on this and other forums has proven a few of the suggested techniques wrong OR completely arguable. To get the full FREE benefit of the SAE one has to study it then come on this forum, search some more or post plan to get "fine tuned" to the best course of action for a build. PITA I say... I've been through many, many changes in my plan as a result... and so have a lot of others. The best single source for up to date info is Rod's book available in the stickies. That being said: 2nd and 3rd layers of gypsum should be screwed, not glued. This allows the layers some movement and improves iso. For a better explanation search for one of Knightfly's 100's of posts about the subject. Only exception to the glue thing is Green Glue www.greengluecompany.com WHICH is not really glue and you still have to use screws. Green Glue used at 100% coverage will make 2 layers of drywall almost act like 4 for iso. Using different thickness of drywall in multilayers, like 5/8" and 1/2" does improve iso in mid range BUT worsens in low end which is what we are after. Better off using all 5/8" drywall. There are some other things I planned on doing only to be shot down by older forum members: Don't think about floating a floor. Search on this forum for floating floor/wooden deck if you need to, almost all of the time it's not the right option. Inside out walls, yup they work, are a space saver but difficult to build and do not have the same STC or TL as a walls built normal. Side wall slot resonators, and slots in general are hard to build. It may be much more simple to just splay side walls and add some absorbers. ME I've not been able to make up my mind yet on using a slot wall or not. Looks like you want to face the long wall in your studio. In small rooms like yours (mine is a bit smaller) we'll get much better result facing the short wall. Larger rooms can face the long wall (and do). There's MORE stuff to be pointed out. The above are some very common things forum members plan on (like me) and then get corrected on. BTW figuring out what you are going to build for acoustics is MUCH harder then figuring how you plan to isolate.... and remember ALL acoustic contraptions in a room will make a third leaf and cause some iso loss (some cause very little, some can cause a lot like a slot wall) so we plan accordingly and beef up iso or take the hit. Marc

n8nod9it wrote:

Yeah that is Masonite... I still wouldn't get water on it for any reason, its a compression fiber product and any water on it would likely swell it, or stay trapped in it, which you wouldn't want layered between gypsum. I don't know how effective that will be in TL isolation. I suppose if you had enough for free, it would be ok to use but it is very thin. Also, that SAE article mentioned gluing the layers together which IMO from what i've read, cause the coincidence frequency of two seperate pieces of material to be merged into one new larger coincidence freq, instead of two seperate frequencies. Two would be better than one, two with GG inbetween would be best. I was going to use MDF in my walls because i could get it for cheap, but i decided not too...Much too messy to cut and heavy. But you'll have to decide whether the Masonite is appropriate after considering its acoustic properties and worth.

right - well seeing as i've actually GOT the stuff, (and it was really cheap anyway) i am just going to put it in the wall as long as it isnt going to make things actually WORSE so i will try to research this - if anyone can point me in the right direction then great and yes at this point i can see that the reasons for wetting this stuff i was talking about would not work sandwitched between two layers of gypsum

guitardad72 wrote:

Bob,

however from the quote on the saecollege site above it says

The SAE site is a great source written by John back in 1998. John no longer has any control of the web site. It's a great intro into the world of studio building, however even John admits part of the info is out of date. Newer research, tests and discussions on this and other forums has proven a few of the suggested techniques wrong OR completely arguable. To get the full FREE benefit of the SAE one has to study it then come on this forum, search some more or post plan to get "fine tuned" to the best course of action for a build. PITA I say... I've been through many, many changes in my plan as a result... and so have a lot of others. The best single source for up to date info is Rod's book available in the stickies. That being said: 2nd and 3rd layers of gypsum should be screwed, not glued. This allows the layers some movement and improves iso. For a better explanation search for one of Knightfly's 100's of posts about the subject. Only exception to the glue thing is Green Glue www.greengluecompany.com WHICH is not really glue and you still have to use screws. Green Glue used at 100% coverage will make 2 layers of drywall almost act like 4 for iso. Using different thickness of drywall in multilayers, like 5/8" and 1/2" does improve iso in mid range BUT worsens in low end which is what we are after. Better off using all 5/8" drywall. There are some other things I planned on doing only to be shot down by older forum members: Don't think about floating a floor. Search on this forum for floating floor/wooden deck if you need to, almost all of the time it's not the right option. Inside out walls, yup they work, are a space saver but difficult to build and do not have the same STC or TL as a walls built normal. Side wall slot resonators, and slots in general are hard to build. It may be much more simple to just splay side walls and add some absorbers. ME I've not been able to make up my mind yet on using a slot wall or not. Looks like you want to face the long wall in your studio. In small rooms like yours (mine is a bit smaller) we'll get much better result facing the short wall. Larger rooms can face the long wall (and do). There's MORE stuff to be pointed out. The above are some very common things forum members plan on (like me) and then get corrected on. BTW figuring out what you are going to build for acoustics is MUCH harder then figuring how you plan to isolate.... and remember ALL acoustic contraptions in a room will make a third leaf and cause some iso loss (some cause very little, some can cause a lot like a slot wall) so we plan accordingly and beef up iso or take the hit. Marc

thanks marc for all the effort you put into replying - i have a question re: the screwing/glueing thing - i may have read this wrong or it may be out of date ... http://www.johnlsayers.com/phpBB2/viewtopic.php?t=502 but i thought it was saying that the OLD recommendation was to screw/nail but that its been discovered that regular glueing is far better Edit - Bob, I've just deleted the above thread entirely - it's only confusing and is covered better in the REFERENCE section. Steve i havent come to that part of the construction quite yet so i can still choose between fixing and glueing but i have already advanced quite a bit so i wont be able to change where i'm facing unfortunatly .. bummer ps looked for rod's book as a digital download and couldn't find it so i suppose it's not availiable that way - wont have time to get it now because the studio will be finished before it arrives and then i have an album to record pronto and all acoustic/studio research will be put on the back burner till we start to do the next album after that ( and given that the rest of the band would have recorded it in an untreated bathroom i'll take whatever i can get at this point ) :roll:

thanks marc for all the effort you put into replying - i have a question re: the screwing/glueing thing - i may have read this wrong or it may be out of date ...

Your welcome. Yup out of date, Steve wrote that in 2003. Here's what Steve wrote on my thread when I was at a similar point of thinking as you:

Drywall - I've clarified the "different thickness" concept in a few places, but they're scattered and NOT in the reference section where you've been looking. I'll reiterate here, and if someone nags enough I'll amend the two main places in the reference section (why hasn't anyone invented 48-hour days (that don't wear you out any more but you get twice as much done ) yet??!? Pluses for differing thicknesses in successive layers in a wall - (NOT GLUED TO EACH OTHER) Differing coincidence frequencies, flattens out the Coincidence dip at around 2-3 kHz by a couple of dB. Minuses for differing thicknesses - confusion on job site, probable wrong thickness applied somewhere, causing tearout Loss of mass, causing worse TL on low end by a couple dB Bottom line is this - if you use all 5/8 you improve bottom end performance, at a 1-2 dB penalty around 2.5 kHz - but since bass is the hard part of isolation, it's better to build for low frequency and the rest will take care of itself. You also remove the chance of screw-ups, cut down on the open floor space you need to store two stacks of drywall instead of one, and improve on your chances for bulk discounts by ordering all the same stuff.

but i thought it was saying that the OLD recommendation was to screw/nail but that its been discovered that regular glueing is far better

IF I understand the historical order of recommendations (strong chance I do not) then 1st was nail/screw, then came gluing, now we're back to screws and even better using the Green Glue. BTW the www.geengluecompany.com is well worth reading even if not using the product.

ps looked for rod's book as a digital download

For Rod's sake I hope that it does not become available as a digital download because then it would be easily file-shared. Rod deserves everything he gets for the book as it is the only and best book of it's kind.

wont have time to get it now because the studio will be finished

Really? I'm mean really.... you are working that fast? That may be an optimum circumstance to build uncorrectable mistakes. Rod's book (in the USA) takes about 1 week to get. My recommendation unless you can absolutely not afford to is to slow down and wait for the book. Marc

thanks again - that really clarifys things yes most of the work on the walls is already done and the rockwool is in so i plan on doing the drywall and caulk over the next 2 or 3 days ( two walls only - the other 2 and ceiling were done already) - and one of them i am not paying that much attention to isolation because there is a very large concrete wall behind it and practically no sound got through to begin with the whole project was meant to be 3 months so am aiming to start recording by end of january i know i could get rod's book for help with the room treatment which i will be doing in january along with the pretty basic instalation (and might do so) - but it wouldnt arrive until at least early jan and the isolation / construction phase will be pretty finished by then i hope not working that fast really - spending all my time on the internet 8) BTW before i stumbled upon john's site i wasnt going to do ANYTHING AT ALL to the room - just record in it - so even spending 3 months at is is a MAJOR shock to the system ( and my drummer - but he'll thank me in the end ) :P

I'd be careful before using the masonite. I've seen the term fiberboard used in this forum synonymously for MDF (medium density fiberboard). So the original recommendation you were opperating on may have nothing to do with Masonite. MDF and Masonite have very different properties and what is true for one may not be true for the other.

actualy in the end i decided to leave it out - it seemed to have as many cons as it did pros and i was also tight for time and all in all it didnt seem worth it - have another use for it anyway thanks all

Maybe I'm wrong but I thought that the term soundboard usually reffered to the fibrous board typically used in construction, especially for flat roofs, installed to reduce rain noise and such. It is 7/16" thick and looks almost like shredded cardboard and some type of fibre all compressed into a 4 by 8 sheet, light to dark brown in color and goes by different manufactures names like donna conna and others I can't remember now. It even comes optional with one side pre-coated for tar roofs. I've used it with great success as part of a wall system, the hardboard that you have though, I can't see doing much. Maybe someone else can chime in here. I think the term needs to be clarified.

Same stuff, Eric - I won't say it's no good, only that given a choice between a layer of soundboard (also sometimes called Celotex) and a layer of drywall vs. 2 layers of drywall, the one with more mass (2 drywall) wins. Period. Now, the diff between a layer of soundboard UNDER 2 layers of drywall vs. ONLY the 2 layers of drywall - you should see a bit more isolation, but then THREE layers of drywall would beat 'em all - and it's not that much more labor and costs typically LESS than the soundboard in most areas... Steve