FINISHED IN 2020! Sharward's Partial Garage Conversion

[knightfly]

When you combine two different mass materials, each has its own coincidence frequency; when you bond them together, you create a new coincidence frequency that's different from either material; it will be related to the AVERAGE mass of COMBINED materials. What it will NOT be, is two SEPARATE and COMPLIMENTARY coincidence "dips" if the materials are bonded together.

In this particular case, you may not have a choice; if your stucco is too uneven, NOT gluing may cause rattles; I would count these as more detrimental than a common coincidence frequency.

One mitigating factor is that coincidence frequency of a combined stucco and OSB leaf, glued together, will NOT be the same as multi-layer drywall of the same thickness; although stucco is approx. 20% heavier than gypsum wallboard and OSB is approx. 20% lighter, your outer wall layers won't be the same THICKNESS as your inner ones so coincidence won't match. 1" of stucco would have a coincidence at around 1250 hZ; 15/32 OSB would have a coincidence of around 3630 hZ; combined at those thicknesses, they would give an outer leaf with a coincidence of about 1500 hZ; 5/8 drywall has a coincidence of around 2530 hZ, same with multi-layers.

If you were to have 1" stucco with 15/32" OSB and 2 layers of 5/8 drywall, you should be aproaching (assuming 12" air gap) STC 79, with TL @ 50 hZ of around 53 dB; using an 8" air gap instead this would worsen to 50 dB @ 50 hZ, but STC would remain at 79. mam would be around 25 hZ with wider gap, 31 hZ with the 8" gap.

Insulation will indeed help damping, but from the tests I've seen GG absolutely KILLS in that respect; I know it's expensive, but using it between the last two layers of wallboard (ONLY; and only on the OUTSIDE wall) would make a noticeable difference in LF TL; and where you're at with your current wall intentions, it would likely make the diff between ALMOST inaudible and COMPLETELY inaudible with live drums. (no other changes - you'd still want to insulate as planned)

Just a thought... Steve

[sharward]

OK. I think I'm getting this, and I think I'm appreciating some of the economies you're talking about.

1" of stucco . . .

Unfortunately, I don't have 1" of stucco. I think I have about 3/8" to 1/2" of stucco on about 1" of styrofoam. (I realize the styrofoam counts for zilch in terms of mass, but at least it's closed cell and is part of the overall outer leaf mass equation.)

I'm assuming I can make up for this less sufficient stucco scenario by adding a third layer of 5/8" gypsum, right?

Also, I've been toying around with using three layers of 1/2" moisture-resistant gypsum panels, like this stuff. I realize that's less mass than 3 layers of 5/8", but since the cleats are only 1 1/2" deep, I figured it would be a cleaner install.

. . . assuming 12" air gap . . .

Yes, that's a safe assumption. (Actually, it will be about 11½" -- so I can use two 6" batts and get slight compression.)

Insulation will indeed help damping, but from the tests I've seen GG absolutely KILLS in that respect; I know it's expensive, but using it between the last two layers of wallboard (ONLY; and only on the OUTSIDE wall) would make a noticeable difference in LF TL; and where you're at with your current wall intentions, it would likely make the diff between ALMOST inaudible and COMPLETELY inaudible with live drums. (no other changes - you'd still want to insulate as planned)

Whew! OK, that's easier to digest. So, we're not talking about using Green Glue everywhere -- just between the final two layers of beef-up gyp ("final" meaning the last two layers installed). I think I can handle that.

I suppose I should also beat this dead horse a bit -- the gaps along the edges of the beef-up strips along the studs. I've pretty much gotten the OK from the brains at StudioTips not to worry about those gaps -- as long as the leaf is air-tight (it is), the cracks shouldn't have much of an impact on TL, particularly the low-end TL I'm working so hard on achieving. (See my question and their answers.) "Speak now or forever hold your peace" on that!

Here's an illustration that clarifies the three options I'm contemplating. Any chance you can do your Insul calculator magic on each of these for me, and comment?

As always, thanks, Steve. You're definitely invited to the grand opening party.

--Keith

[sharward]

Progress! My "beef-up base OSB" on the east wall is pretty much done now, except two narrow cavities (each about 3-5" wide) which I'll deal with last.

I was hoping to tear off more drywall today, but I was working at a pretty slow pace today.

Doesn't this OSB just look like it's screaming for some beef?

Steve, questions for you are in the previous post.

--Keith

[bondsong]

Looks nice Keith! It's funny how we start appreciating pictures of framing and such after being here for a while.

Frank

[mikeklooster]

yeah ever think youd be sneakin around at night just so you could see them....oh shit my wifes coming!

[sharward]

Ha! Thanks guys... I know exactly what you mean. I'm glad you appreciate the progress reports and photos.

It's a motivation factor for me too. Yesterday I almost quit before finishing those top pieces, but the thought of taking the pictures and posting them here gave me the boost I needed to finish up.

--Keith

[Stick]

Looks good Keith...

So, one little question. I'm still a litte foggy on the cleat system in the beef-up wall. The OSB is not screwed to anything right? Is it glued? The cleat screwed to the stud is holding it in? Then you screw the drywall to the OSB?

Is that the idea?

[Stick]

Ok, nevermind. I just went back and read up on what I'd missed the last couple days... glue, then cleats. Makes sense. All good.

Get back to work.

[sharward]

Right you are, Stick. I can't screw drywall into styrofoam -- and even if I could, I'd be penetrating the building paper all over the place, which would defeat the purpose of the paper being there.

[Stick]

I'll be doing the same thing, but to an interior wall that is just 1 layer of 1/2" drywall... is there a way to do it without the OSB layer? Could I get 2 layers of 5/6" drywall up against it somehow with cleats? I dont' think I'd be able to screw them together is the problem... glueing drywall together doesn't seem that cool... hmmm...

Of course, doing the OSB, then 2 layers of drywall would probably wouldn't hurt... and since I'll probably be able to do that bit myself, it won't cost me any more labor time.

[sharward]

Hey Stick,

I suppose it may be possible to use cleats between the studs to hold two "strips" of drywall firmly against the oposing layer. However, I'm going to go ahead and use OSB, since (don't shoot me ) I have 10 foot ceilings and I'll actually be putting up the beef-up panels in two halves -- roughtly 6 feet tall and 4 feet tall, staggering the seams (4 on top, 6 on bottom; 6 on top, 4 on bottom; etc.). This is so that I don't have to worry about 10 foot tall narrow strips of drywall breaking during installation... Plus, I think they'll be generally easier to work with. Finally, the OSB does offer a fair amount of mass for isolation and it offers a differing resonance frequency, so it's not a total waste of money, effort, or space. It's also not too expensive (a little less than double the price of a panel of drywall).

The only thing that sucks a bit is that it must be cut with a circular saw on my sheet rack... although I'm getting pretty efficient with that.

Stick, I'll probably be ripping some more OSB strips and cleating them into my south and west walls next weekend... Let me know if you'd like see the operation live and in person!

--Keith

[Stick]

Stick, I'll probably be ripping some more OSB strips and cleating them into my south and west walls next weekend... Let me know if you'd like see the operation live and in person!

--Keith

Not that I wouldn't LOVE to come and help , but my Dad is going to be in town to help out with some landscaping projects we're in the midst of: spreading some topsoil, laying sod, planting a hedge, and then he's going to help me attempt to fit what's in the garage now into the rather small shed so that the studio demolition can commence when permits allow... actually, that's a good question for you... am I supposed to have the permit to take the place apart? The outside walls pretty much have to be rebuilt, and getting the ugly 4 inch thick rock off them is going to be a pain the neck (and back, and arms).

[sharward]

am I supposed to have the permit to take the place apart?

I don't know the official answer to that, but in my mind, demolition is a part of the project, and since the project shouldn't begin without the permit, nor should the demolition. That's the safe answer. You'd need to ask friendly local bureaucrats to determine the real deal with that.

--Keith

[Stick]

Makes sense. Thanks.

[sharward]

I spent most of the day removing the gypsum from the south and west walls -- 18 linear feet, about as much as the east wall I worked on the last couple of weekends.

Unfortunately, I made a not-so-good discovery: there's a layer of OSB that is already attached to the garage side of the south wall! In the back of my mind I was half-way expecting this. It made it more difficult to remove the gypsum, but partway through the job, it occurred to me that removing the OSB is not without consequences -- it's there for seismic stability! So the plan of removing all of whatever is on the garage side and beefing up the interior wall between the studs (as I will be doing with the south wall) must be changed.

Here are my options (the first two of which aren't options):

1. Remove the OSB and replace it with diagonal bracing after beefing up the wall between the studs. However, I'm not a fan of this approach, as I believe the OSB is stronger than diagonal bracing. Plus, there are literally hundreds of nails holding the OSB to the studs -- removing it would not be fun.
2. Remove the gypsum from the interior side (my carpeted office in the house) and beef up the garage side from the interior, then cover the studs with cloth. Nope! Forget it!
3. Leave the OSB where it is -- add multiple layers of gypsum to it and live with a third leaf effect. I figure three layers of 5/8" with green glue between the final two layers will do the trick. Heck, since I'm not dealing with cleating strips, I might even do four layers of 5/8" in an effort to compensate for leaf #3.

I'm not thrilled about this discovery because it means losing a few precious inches of space in my already tiny room. At least it's in the direction that I can afford it the most (i.e., not making my room skinnier).