MDF, Plywood or Drywall for internal walls?
Timmeh!
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#1
22nd July 2009
Old 22nd July 2009
  #1
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MDF, Plywood or Drywall for internal walls?

Is there much difference in terms of frequency response or resonance problems between MDF, Plywood or Drywall as internal walls, given the same all are the same thickness? For instance, I have heard that MDF can sound 'honky'. I am keen to use either Plywood or MDF but like the idea of having greater mass per buck with MDF as budget is a concern. I'd consider drywall however I have a carpenter friend who can do the wood panelling for next to nothing.
Thanks in advance.
#2
22nd July 2009
Old 22nd July 2009
  #2
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DanDan's Avatar
Mass

Most people seem to end up using Drywall. Most designs use double layers of drywall (on each side) to achieve Mass. I very much doubt that the Ply or MDF will beat the Mass per Buck and ease if installation/finish of Drywall.
DD
#3
22nd July 2009
Old 22nd July 2009
  #3
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Glenn Kuras's Avatar
 

agreed and you could use green glue between layers of drywall to help with iso.
#4
22nd July 2009
Old 22nd July 2009
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nosebleedaudio's Avatar
 

I've used plywood for a couple of good reasons;
One; when you add several layers of material you DON'T have to rely on hitting a stud...
PLUS if you plan on attaching other things to the walls/ceiling such as panels,diffusors ect. it is superior to NOT having it...
In a few studios I designed I demanded 3/4" ply for certain places..
My .02cents.
#5
22nd July 2009
Old 22nd July 2009
  #5
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tINY's Avatar
 


I would think that MDF would actually perform pretty well. But, repair and finishing are hard.




-tINY

Timmeh!
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#6
22nd July 2009
Old 22nd July 2009
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Thanks for the comments. I was going to go with drywall until my carpenter friend said he can put up timber paneling instead for next to nothing. I've had some rough quotes for drywall installation and the labour seems pretty pricey, though the product not so - and they basically say its going to take 10 days or more to finish the job. Its only a 6.5x3.5m space, so I was surprised they said it would take so long. This is why the timber option is preferable to me - much cheaper labour costs and with MDF the mass per buck doesn't seem to be that much more than drywall, whereas ply is considerably more expensive, from information I have found. I was just concerned about and sound or frequency issues if I went with MDF as its not a true wood product - that's really my biggest concern.

Last edited by Timmeh!; 22nd July 2009 at 10:40 PM.. Reason: more...
#7
23rd July 2009
Old 23rd July 2009
  #7
You can also research sandwiches: GWB - something else - GWB

GWB is just drywall or sheetrock. Call it what you will. The "something else" can be Celotex, plywood, or MDF etc. Each will behave a little differently. I wouldn't use only wood, but as an extra layer it can be used to good effect.

Apart from the impact on sound isolation, I echo the practical comment above about being able to attach anything anywhere without need of studs. This is most true with ply (the thicker the better), though with MDF under a layer of drywall, if you use the right screws and pre-drill, it can work just as well for most applications.
Timmeh!
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#8
23rd July 2009
Old 23rd July 2009
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Thanks, I will look into that. So if I already have a layer of MDF up (say 19mm), would it be just a case screwing the drywall into the MDF?
#9
23rd July 2009
Old 23rd July 2009
  #9
Lives for gear
My dig's are essentially 3/4" OSB and 2 layers of 5/8" gypsum with green glue between the gypsum.

The use of MDF is good, but what I have experienced with MDF is that once you put a screw to it, that hole is pretty well done for. In that the MDF is too soft to allow repeated screw application.

OSB and plywood do not normally exhibit this characteristic, and therefore, IMHO, a better product for studio construction.

Since you already have the MDF up, I wouldn't go back and remove it unless it is on the ceiling and you are concerned about screwing through the gypsum and into the MDF with any kind of extended weight.

Otherwise, if you are going to use a single layer of gypsum, then apply green glue to the gypsum as you screw it to the MDF.
Timmeh!
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#10
23rd July 2009
Old 23rd July 2009
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The MDF is not up yet, just curious about the process of attaching the drywall to it.
Thanks for your suggestion - I'll definitely look into the green glue.
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#11
23rd July 2009
Old 23rd July 2009
  #11
Quote:
Originally Posted by Timmeh! View Post
The MDF is not up yet, just curious about the process of attaching the drywall to it.
Thanks for your suggestion - I'll definitely look into the green glue.
Yup, you can just screw the GWB up as in a normal drywall job; but again, MDF can break apart when trying to screw into it, so you'll probably want to drill small pilot holes. Green glue can be used with GWB/MDF just as well as GWB/GWB. Be aware of the long cure times before you can judge the full effect.

And good safety caution above about the ceiling. You may want to get longer screws that can go through the MDF to the joists if there's weight above your head.
Timmeh!
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#12
23rd July 2009
Old 23rd July 2009
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Thanks Jay, appreciate the advice.
R_O
#13
23rd July 2009
Old 23rd July 2009
  #13
R_O
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It's about mass. GB and MDF have about the same density. (around 700kg/m3). Plywood is much lighter. you'd end up with thicker walls using plywood to compensate the mass.

GB is known to be a great product since it has mass and is cheaper than MDF. It's easy to work with too.
#14
23rd July 2009
Old 23rd July 2009
  #14
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Quote:
Originally Posted by Timmeh! View Post
The MDF is not up yet, just curious about the process of attaching the drywall to it.
Thanks for your suggestion - I'll definitely look into the green glue.
Ahhh... that's what I get for working all day on two hours of sleep and then trying to comprehend... (Hell, comprehension after 8 hours of sleep is bad enough)

I had originally wanted to use MDF, but the cost was almost double that of the OSB I ended up using. So, thankfully, cost factors drove me to a better product.

I used 2" drywall screws to attach the OSB to the studs. Then 1-1/2" drywall screws to attach the 1st layer of gypsum to the OSB, and 3" decking screws to attach the 2nd layer of gypsum.

As far as glues and adhesives...

I used PL400 on all the ceiling joists when I put the OSB up... and PL400 when I put the OSB up on the walls of the tracking room. A single wide bead along the joist/stud.

After attaching the OSB, in a horizontal orientation, I stuffed backer rod around the perimeter of the OSB at the ceiling, vert wall corners and floor. Then I sealed all the joints with OSI's SC-175 acoustical caulk.

For the first layer of gypsum, I attached this layer in a vertical orientation. I used OSI's drywall adhesive in a random pattern and 1:1 - tube to gypsum ratio. Again, I caulked the corners and used backer rod to stuff the corners, and sealed them with OSI SC-175 and in the Control Room, I switched over to Green Glue Corp's, SilenSeal.

I wanna mention the SilenSeal product... It may be a pseudo "better" product than the OSI on paper, but I have some real issues with this stuff... It's a MAJOR PITA to work. It sucks as far as handling. The 7 cases of tubes I purchased had major issues, in that there was a massive air bubble in over 3/4 of the tubes. It causes the caulk to continue flowing after you take pressure off the gun... and the shit came exploding out of the tube when I got down to that bubble. On more than one occasion, the blast blew the caulk out of the joint and it created one hell of an aggravating mess.

Another thing I discovered is that it has one hell of a shrinkage problem... The stuff exhibits about a 50% shrinkage. So, you end up using twice as much caulk as you do with the SC-175. But since the SilenSeal is about as thick as baby shit, you can definitely fill whatever gap you're filling. And it does fill the gap better than the OSI since it is such a thin viscosity compared to the OSI... but if I had it to do over... I'd use the Silenseal on the OSB and the OSI on everything else.

I used Green Glue for the Iso Booth and Tracking rooms in a 2:1 - Green Glue to Gypsum ratio. When putting the Green Glue down, you want to put down pretty wide beads... not thin beads. The recommendation I got was to make the beads at least 1/4" wide or wider. Oh... and this stuff is sticky... not just a little... but SERIOUSLY sticky. Don't let the stuff get on anything you don't want it to stick to, or stick to it... EVER. I accidentally got some on the floor and on a couple of pieces of scrap OSB. almost a year later, the scrap OSB is STILL sticky as hell and anything that touches it... oof. You'll play hell getting it un-stuck. (yeah, I hung on to it just to see how it acts.)

The thing that I think actually helped get the STC up as high as it is, was the screw patterns (and the 24" OC stud spacing) used to attach the OSB and gypsum. I used the info Rod supplied in this sticky at RO. (Click on the Gypsum Construction Handbook at the USG site.)

The key is to get a good consistent screw spacing. I worked as hard as I could to keep a 16" spacing on the screws for each layer. I had quite a few folks tell me I was insane using that many screws on each board. Then too, the proof is in the pudding, as they say... but the goal you are trying to achieve is not just to get the shit on the walls. The goal is to try to make your walls (and ceilings) one homogeneous mass. Unless you use enough fasteners, you'll not quite achieve that goal.
#15
23rd July 2009
Old 23rd July 2009
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R_O
#16
23rd July 2009
Old 23rd July 2009
  #16
R_O
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Quote:
Originally Posted by xaMdaM View Post
I had originally wanted to use MDF, but the cost was almost double that of the OSB I ended up using. So, thankfully, cost factors drove me to a better product.
"better"? OSB is about 500kg/m3... less mass, less isolation. What's better about OSB?
Timmeh!
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#17
23rd July 2009
Old 23rd July 2009
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Just to clarify, I'm in Australia, but I believe most of those products are available here, just sometimes different names.

I'd like to know more about OSB - if it is that much cheaper then it maybe an option.
#18
23rd July 2009
Old 23rd July 2009
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QuietRock 510 is about $50/4x8 sheet

5/8" FR Gypsum is about $8/4x8 sheet
Green Glue is about $26/4x8 sheet (2 tubes/sheet)

So... $50/sheet vs $34/sheet and better LF TL with Green Glue..... I'll take the Gypsum/Green Glue every time. All you have is a bit more work and less convenience, but IMHO, the GG is a much better solution all around.
#19
23rd July 2009
Old 23rd July 2009
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Quote:
Originally Posted by R_O View Post
"better"? OSB is about 500kg/m3... less mass, less isolation. What's better about OSB?
Hey ro!

So, you get over here too, huh?

What I meant, and evidently didn't quite convey, is that with MDF, it's much easier to strip a screw hole, and/or if you need to back a screw out and put it back in, the MDF isn't as stable as the OSB from the aspect of a fastener.

Also, MDF chips and breaks much easier than OSB in general handling.

One other thing I've noticed is that MDF seems to more readily absorb moisture. At least with the MDF that I have access to here, it swells much more than I would have expected. I have 3 sheets still sitting here that I'm about to put on my interior doors. (Rod's Super Door design) and have noticed that the end cut pieces from a previous door installation are swollen and the edges are chipping quite a bit. Whereas, the OSB that I have, is quite a bit more stable and has not swollen at all.
Timmeh!
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#20
23rd July 2009
Old 23rd July 2009
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Thanks for all that advice xaMdaM. I can't get the Quietrock here in Oz anyway, so that's out of the equation. I can get the green glue and there are plenty of plasterboard (drywall) options as well. I will look into OSB too, I'm I know the manufacturer supplies to most decent hardware stores.

I am slightly worried about using MDF as I live in a humid - tropical climate and it may swell. How much, I don't know. Saying that all walls and ceiling will be insulated with at least 60mm rockwool.

The other thing I am thinking about for the ceiling is a layer of MDF (or OSB) and instead of gypsum, using pine or bamboo flooring to get a nice look. I can get 15mm bamboo very cheap at the moment. How much it will add to sound isolation, i'm not sure about either, but it would look good in a catherdral shaped roof - which I am planning.
#21
23rd July 2009
Old 23rd July 2009
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Quote:
Originally Posted by xaMdaM View Post
QuietRock 510 is about $50/4x8 sheet

5/8" FR Gypsum is about $8/4x8 sheet
Green Glue is about $26/4x8 sheet (2 tubes/sheet)

So... $50/sheet vs $34/sheet and better LF TL with Green Glue..... I'll take the Gypsum/Green Glue every time. All you have is a bit more work and less convenience, but IMHO, the GG is a much better solution all around.
Quiet rock is advertised at $40 /sheet. MSRP is $50, but no one actually charges MSRP for the stuff do they?

$6/sheet difference isn't much considering all the GG labor. Overall STC seems comparable.
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#22
23rd July 2009
Old 23rd July 2009
  #22
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Quote:
Originally Posted by mobius.media View Post
Quiet rock is advertised at $40 /sheet. MSRP is $50, but no one actually charges MSRP for the stuff do they?

$6/sheet difference isn't much considering all the GG labor. Overall STC seems comparable.
I dunno... it took me all of 3 minutes to put the GG down... but I also wouldn't call 3db improvement in LF TL a comparable number.

At any rate, the OP's not able to get QuietRock anyway... so it's a moot point.
#23
23rd July 2009
Old 23rd July 2009
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Quote:
Originally Posted by Timmeh! View Post
The other thing I am thinking about for the ceiling is a layer of MDF (or OSB) and instead of gypsum, using pine or bamboo flooring to get a nice look. I can get 15mm bamboo very cheap at the moment. How much it will add to sound isolation, i'm not sure about either, but it would look good in a catherdral shaped roof - which I am planning.
I'd go for OSB/MDF/Plywood, then a layer of gypsum (w/GG) and THEN your finish.

You can't have enough mass IMHO... and gypsum just gives you so much mass/dollar, that it's well worth the cost.
#24
23rd July 2009
Old 23rd July 2009
  #24
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Quote:
Originally Posted by xaMdaM View Post
I dunno... it took me all of 3 minutes to put the GG down... but I also wouldn't call 3db improvement in LF TL a comparable number.

Ya just found comparison specs:
http://www.soundisolationcompany.com...-quietrock.pdf

Also I notice quiet rock 510 has no fire rating which obviously sucks for that option. FR gypsum - I assume you mean it had a fire rating in hours.

Where do you get GG so cheap?
R_O
#25
23rd July 2009
Old 23rd July 2009
  #25
R_O
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Quote:
Originally Posted by xaMdaM View Post
Hey ro!

So, you get over here too, huh?
jup, not as active as "the other" forum tho

Quote:
What I meant, and evidently didn't quite convey, is that with MDF, it's much easier to strip a screw hole, and/or if you need to back a screw out and put it back in, the MDF isn't as stable as the OSB from the aspect of a fastener.
Also, MDF chips and breaks much easier than OSB in general handling.
hmm, I have that with OSB. I get much cleaner cuts with MDF. I agree it's less "stiff" so it's fragile.

Quote:
One other thing I've noticed is that MDF seems to more readily absorb moisture.
True. MDF is sensitive to moisture. Keep it in a dry place. Most wood will absorb moisture anyway but MDF makes a mess when it's wet. The key is to put on a paint base coat as soon as possible.

I love to work with MDF, much more than OSB. all a matter of choice

But MDF is heavier, so it outranks OSB concerning mass.
#26
23rd July 2009
Old 23rd July 2009
  #26
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Quote:
Originally Posted by mobius.media View Post
Where did you find comparison specs?

Also I notice quiet rock 510 has no fire rating which obviously sucks. Which gypsum did you use and did it have a UL rating in hours?
Green Glue -vs- Factory Damped Panels

I used standard 5/8" FR gypsum products from Lowe's and Home Depot. (Thankfully, all my gypsum was locally manufactured and not made with the now infamous Chinese gypsum.)
Sen
#27
26th July 2009
Old 26th July 2009
  #27
Sen
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No probs screwing into MDF here..If you try and screw into the side of it (thickness wise)- forget it, but otherwise it will hold the screws in pretty safely. I have a layer of 18mm MDF hanging on RC-1 on my LR ceiling + a layer of 10mm plasterboard and nothing's fallen down or cracked in 2 years.
HAving 2 (or more) different materials as your layers is better than a few layers of the same material definately.
Also...don't worry about ppl saying MDF sounds "honky"...you use things like MDF for soundproofing, and should use other stuff for sound treatment/shaping when the walls/ceilings are built. Diffusion and absorption will determine how your room "sounds"
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