2nd layer of wallboard/ single frame wall

[gigpiglet]

i am in the proccess of constructing a studio (for a very modest budget)
the walls are single frame 2x3.

10mm "soundcheck" plasterboard (cause it was cheap) on one side.
tontine fiber insulation in the cavity.
19mm ply (cause it was free) and
10mm plasterboard on the other side.

my question is: what is the best way to fix the 2nd layer of plaster to the ply?
i have searched this forum, but all of the material seems to relate to a double stud wall....
what is the best for a single stud construction?

glueing?
screwing?
both?

thanks

[knightfly]

Neither; if you've not already fastened anything to the inside surface of your studs, you need to find some sort of RESILIENT mounting system; the least expensive in most areas is Resilient Channel - here's a pic of what you want, several different manufacturers make it -

http://www.dietrichindustries.com/produ ... _46-47.pdf

With single frame construction, you will gain about 8-10 dB of isolation in mid frequency range by using this approach; at lower frequencies, it's not much difference one way or the other... Steve

(More to read in the REFERENCE section at the top of this forum.

[rod gervais]

Neither; if you've not already fastened anything to the inside surface of your studs

BTW,

This means that if you have already fastened the plywood to your studs - you have to remove it - or live with the fact that your isolation is going to be poor at best (do not put rc over the plywood).

As far as fastening to the plywood - if you aren't going to use resilient channel - you may as well screw right into the studs with your drywall screws - because you won't gain any isolation by screwing into the plywood itself.

Rod

[sharward]

Right. Stick with "two leaves." (If you're not familiar with why that's critical, then go through go the "Before You Post" announcement.)

[jgreen77]

My 20' x 20' garage space is coming along, but after a drum kit test yesterday we were very disappointed with sound transmission thru to the outside. To recap - I took an existing garage and insulated between the studs, put MLB on that and then a single layer or 1/2" TH drywall. On the back wall and half of two side walls, there is an approximately 18" high concrete wall to which the stud walls are on. This concrete seems to be a week point in my wall. The concrete is not flush with the drywall, it sticks out a bit. I will post pics later tonight and wait for you gurus to chime in.

[sharward]

So it seems that the lower 18" of your wall is single leaf concrete, while the rest of your walls are two coupled leaf with minimal mass.

I can see why you're disappointed with the results.

You need mass-air-mass, with increased amounts of each as much as feasibly possible (i.e., lots of mass, as much air as you can afford, and then lots of mass again). This concept is covered extensively on this thread, which is linked from the "REFERENCE AREA" Announcement, which of course is linked from the almighty "Before You Post" Announcement -- which you did read -- right?

I hate to be the bearer of bad news, but if you want significant improvement over what you have, you'll probably have to tear out what you installed, beef up your outer leaf by adding multiple strips of gypsum wallboard between the joists as described in BilWare's "Attaching drywall between joists" thread, and building a new inner frame alongside the existing walls with multiple layers of gypsum wallboard attached to it and, of course, lots of insulation between the leaves. You'll need to have a door in each leaf, and your ceilings/roof will have to be in the same league -- otherwise, it's a big waste of time and materials.

I'm assuming "MLB" is a typo and that you meant "MLV" (as in "mass loaded vinyl")...? Gypsum wallboard gives you much more mass per dollar.

[jgreen77]

You have ruined my day - but I appreciate it (really). I do understand the mass-air-mass, but you say my leafs are coupled (no good). I would consider an additional internal wall, but then I still have a ceiling to contend with.

Maybe I will just turn the space into a bar where I can drown my sorrows. Thanks guys for all your help!!

[Dan Fitzpatrick]

This concrete seems to be a week point in my wall.

jgreen,

i don't think that the concrete is the weak point, it is almost certainly your walls on top of the concrete.

a wild-ass-guess: the concrete probably is better than the wall you describe by around 10db

4" of concrete (you probably have more) has an STC of 47 and your wall is most likely in the 30s somewhere.

but if you do mass-air-mass all around you will do better than either the concrete or the existing wall by itself.

if you want some good ideas on wall construction (and data) look through this pdf:

http://irc.nrc-cnrc.gc.ca/fulltext/ir761/ir761.pdf

dan

[sharward]

Maybe I will just turn the space into a bar where I can drown my sorrows. Thanks guys for all your help!!

Aww, man... Does that mean you're giving up?

[jgreen77]

I am not giving up yet. I have been in contact with another person from this forum who has had a very similar issue in the past, and said he had very good success with the same construction, but with another 5/8" layer of drywall. I cannot tear down the walls (because my wife will kill me) so I am adding mass. Later on down the line, I will consider adding another internal wall. I am also considering adding a small soffit/bench of sorts around the bottom to cover my concrete...

[knightfly]

If you can't rip out the 1/2" gyp, then first make SURE everything that's there is SEALED - acoustic rated caulk is cheaper than the regular stuff, just harder to find. Even a crack that's 1/64" wide by 3-4 feet long will reduce wall performance several dB.

Next, if possible add TWO layers of 5/8, make sure you mud and tape ALL joints for EACH layer. All you've got going here without ripping out and re-framing, is MASS - it takes DOUBLE the mass to improve by 5-6 dB, this is across the board from low to high frequency. This is calculated for BOTH sides of a mass-air-mass partition, so you will probably gain about 6 dB over your existing single layer of 1/2" with two layers of 5/8 added. (Since this will only be on ONE SIDE of the wall) -

Be sure to stagger all seams by at LEAST a foot, two is better - seal it like you were building a BOAT, into which you would place your two hundred most valuable possessions.

Gypsum is usually tapered along the longer dimension; make sure this taper faces OUT (toward you), and bring the surface up FLUSH with the UN-tapered parts with mud, then tape and smooth, let dry, sand, and do the second layer.

This joint area can be another weak spot; not only would you end up with lower mass at that location by NOT mudding, but also you would be creating a small triple leaf section that would weaken the isolation even further at that location.

Bottom line: don't expect miracles, but two layers of 5/8 properly applied WILL give you a very noticeable improvement over what's there... Steve

[jgreen77]

We seem to be on the same page and the same sentence. We filled every gap we could find with acoustic caulk and every seam on the first layer of drywall was taped & mudded. The second later will be just as meticulous as far as filling every gap. I know how hang to drywall fairly well, so no worry there. I also have a source for caulk nearby, no I can get another case if I need. Thanks again everyone for all your help!

[knightfly]