building studio: question about screws for drywall

[grexter]

hi guys,

im in the process of constructing my studio and it will have two layers of drywall (sheetrock/gypsum boards) each 5/8" thick. What length of screws are "recommended" for the first and second layer?

thanks in advance

g

[DSD_Mastering]

We just finished our build. Use 1 1/4" and 2 1/4"
I'd also suggest using Green Glue inbetween the layers!

Regards,
Bruce

[drBill]

If you can get the floating channel to float them on and make sure no one hits a stud - only into the channel and the channel into the studs, you'll get much better isolation. BUT, it's critical that whoever's screwing the drywall makes SURE to never hit a stud - only the channel. I forget what it's proper name is, but it's cheap and easy to do.

[grexter]

thanks - thats pretty much the screw lenght my contractor got (he got 2 1/2 for second layer) I wanted to check as he already "screwed up" quiete a few things in the construction so I feel like I really have to double check everything now...

btw, just a note for guys who plan to construct a studio and actually get someone (a contractor) to do the job... a little piece of advice: as much as possible try to be there all the time or else you'll have some very nasty surprises, trust me and then you'll have to spend twice as much money and time trying to correct the stuff they did wrong

[idylldon]

Originally Posted by drBill

If you can get the floating channel to float them on and make sure no one hits a stud - only into the channel and the channel into the studs, you'll get much better isolation. BUT, it's critical that whoever's screwing the drywall makes SURE to never hit a stud - only the channel. I forget what it's proper name is, but it's cheap and easy to do.

Resilient channel, but a better way to mount the second layer is here:

RSIC-1 - Resilient Sound Isolations clips

The second layer of drywall mounted with these clips and "hat" channel (used in metal framing) gives a real nice STC rating because the drywall actually flexes and absorbs the bass frequencies. I used these in my build and I couldn't be happier with the result.

Cheers,
--
Don

[rockstar_josh]

Yeah, when I built my rooms I hired some help on certain parts of it and it was like pulling teeth to get people to do things the way I wanted them to. When you're asking normal construction guys to do things for soundproofing for the most part they're not going to understand the importance of the engineering involved; they're going to fight it and insist on doing things the way they're used to, it's faster, less work, blah blah blah.... they're used to doing things a certain way and of course they're extremely efficient at it, but that's in the "real" world, not studio construction. It's asking a tiger to change his stripes.

[drBill]

Originally Posted by idylldon

Resilient channel, but a better way to mount the second layer is here:

RSIC-1 - Resilient Sound Isolations clips

The second layer of drywall mounted with these clips and "hat" channel (used in metal framing) gives a real nice STC rating because the drywall actually flexes and absorbs the bass frequencies. I used these in my build and I couldn't be happier with the result.

Cheers,
--
Don

Nice Don!

[666666]

Originally Posted by idylldon

the drywall actually flexes and absorbs the bass frequencies...

But if that's the case, won't the drywall resonate and cause issues inside the room? I once put up a heavy drywall wall in a semi-floating manner, and you could punch that wall and it sounded like a giant bass drum. It wasn't good.

In many cases, it is recommended to secure drywall tight to studs, and even add lots of extra blocking to the framing, then gluing the drywall to all framing to keep the drywall as "tight" as possible so it resonates as little as possible. I'm sure I'm overlooking something here... but if drywall is too loose, I'm pretty sure it will resonate badly at the resonant frequency... which is most likely going to be a problem inside the room, even if it DOES help absorb sound and thus increase the STC.

Help me understand this... in the meantime I'm still into the idea of building two separate isolated walls, screwing / gluing the drywall down nice and tight to the framing. Even then the walls will resonate, but... I'd think you'd want to reduce this as much as possible. Then again, one acoustician once told me that you can never kill all resonance, so the best thing to do is dial in a resonant freq range that will be easy to tame later... meaning higher than lower freqs.

And having said all this, I've been in rooms that were slapped together by monkeys, everything done wrong, covered with cheap foam etc, and they yielded great recordings. Perhaps just a lot of luck and black magic with this stuff in general.

[drBill]

It's what I was told to do. I've got double walls, and the wall on the "inside" is not floated with resiliant channel. The dry on the outer wall is floated.

[idylldon]

I have never experienced a problem with it resonating, which could be due to the fact that it's not that loose. You have to push on it pretty hard to feel it flex at all. The inside layers of my walls are one 5/8" layer of drywall screwed to the 2x6 studs, a layer of loaded vinyl, a layer of 1/2" homasote, and then the RSIC/hat channel with another layer of 5/8" drywall screwed to it. My walls definitely don't sound like a bass drum.

After all that, I lined the walls with two different styles of membrane/panel traps for bass control alternating with burlap covered 703 to control a bit of the highs and mids and to reduce the reverb time. I used Ethan's plans on his website and they work very well. All the traps are 2'x8'.

I've done a lot of recording in this space and have never had any resonance issues that I can hear or that I've measured when testing the room. Maybe I just got lucky or something.

Cheers,
--
Don

[avare]

Originally Posted by 666666

But if that's the case, won't the drywall resonate and cause issues inside the room?

ALL two leaf partitions, including with concrete, have a resonance. As an example of it, have look at pdf page 7 here. If you want to see it graphically have at the tests of 350 walls in IR761.


It normally does not cause a problem room acoustics. Have you ever noticed a ringing in a room with stud walls?

Andre

[Sigma]

Originally Posted by grexter

hi guys,

im in the process of constructing my studio and it will have two layers of drywall (sheetrock/gypsum boards) each 5/8" thick. What length of screws are "recommended" for the first and second layer?

thanks in advance

g

dude wrong way to build..if you are double sheeting you should use reg drywall over green rock and both should be different thickness' .. you block much more sound that way

if ya really wanna do it right sandwich high compression vinyl between the boards..you can get it from acoustics first online

[avare]

Originally Posted by Sigma

should be different thickness' .. you block much more sound that way

if ya really wanna do it right sandwich high compression vinyl between the boards..you can get it from acoustics first online

While true in that different thicknesses will yield a higher STC, it is not important for music. With music, the difficult sounds are lows. If you look at pdf page 227 in IR761 (linked in my previous post) , you will see a dip in the TL centred around 2.5k. This the coincidence dip caused by the material properties that are the same for all the layers with the same thickness and material. Yes, if different thicknesses are used the dip will be shallower and wider, increasing the TL by several dB. This will also increase the STC. This where there is over 60 dB of TL already! The low end will be worse, because of less mass. The low has as little as 16 dB of TL. So the improvement, is in a range where there is more than enough isolation already!

MLV and its relatives have valid uses in acoustics, but not in partitions. It is cheaper and more effective to put an additional layer of drywall etc.


Andre

[Sigma]

Originally Posted by avare

While true in that different thicknesses will yield a higher STC, it is not important for music. With music, the difficult sounds are lows. If you look at pdf page 227 in IR761 (linked in my previous post) , you will see a dip in the TL centred around 2.5k. This the coincidence dip caused by the material properties that are the same for all the layers with the same thickness and material. Yes, if different thicknesses are used the dip will be shallower and wider, increasing the TL by several dB. This will also increase the STC. This where there is over 60 dB of TL already! The low end will be worse, because of less mass. The low has as little as 16 dB of TL. So the improvement, is in a range where there is more than enough isolation already!

MLV and its relatives have valid uses in acoustics, but not in partitions. It is cheaper and more effective to put an additional layer of drywall etc.


Andre

lows are the worst but i have neighbors [rowhome] low end rumble is less offensive than higher frequencies and i wasn't about to put up 3 layers of drywall..i fig if you are doing the double wall at least change up on density and type drywall

i haven't been in many pro studios where ya can't hear bottom coming out from the walls

will check out you link

my room is covered in acoustic carpet so it has no high end ring..it's not dead just warm

[stevep]

Originally Posted by Sigma

i haven't been in many pro studios where ya can't hear bottom coming out from the walls

True, bass is so hard to stop

65 db is a good number to shoot for, remember, your sound proofing is only as good as the weakest link, so if you have a wall thats 80 db and just put a 20db door or window in you wasted all that time on the 25 layers of drywall and floated floors


And, the more soundproof the room is the more acoustical treatment/absorption you need


And for your RC and having a contractor install it

Even if one screw hits a stud you just wasted all that RC

and it might even be worse than if you just fastened the DW direct to the studs



To address the damping issue,.. make sure to use 6" of fluffy insulation in the airspace, it needs to contact both sides of the double wall to dampen it but not to tight or it will couple the double wall


Also make sure they leave a 1/4" gap for acoustical caulk on all edges

and watch them ! they love to skimp when it comes time to mud, tape and caulk

...... its probably to late :((

[Chris Kress]

Originally Posted by drBill

If you can get the floating channel to float them on and make sure no one hits a stud - only into the channel and the channel into the studs, you'll get much better isolation. BUT, it's critical that whoever's screwing the drywall makes SURE to never hit a stud - only the channel. I forget what it's proper name is, but it's cheap and easy to do.

"s channel" I think

[Doublehelix]

I am doing my entire build myself, but I did have some contractors in to do the framing, and it was like pulling teeth to get them to understand some of the concepts I was trying to get across to them,

For example:

A room-within-a-room cannot have *any* contact points with the outside walls. They thought I was just being overly paranoid, and kept trying to tie in a few studs here and there with the outside walls for extra support. NO!!! Do it again, and do it the right way! I am paying you to do a job, and I want it done a certain way... otherwise, I will find someone else. They grumbled a lot, but ended up doing it right. Funny though, they must have asked me about 3-4 more times if it was OK if they just put "one nail" and a small piece of wood between 2 walls for stability. NO! Build it *this* way instead! Sheesh! Contractors!

I used RC on a ceiling in one of my rooms for some extra isolation from the room above, and you really do have to be careful. I would never trust *any* contractor to do it right. As Steve says, just hit one stud, and you just wasted a whole lot of time and money. I marked the position of the studs on each of the two drywall layers, and made sure that my screws came NOWHERE near the studs. I did my RC using 16" OC spacing, even though I was told I could use 24" OC. I wanted to make sure that there were enough screws to hold the weight since I am spacing the screws away from the studs.

[jchas]

I can't speak to which method is better acousticly, but from a construction perspective, if you're going with the high-compression vinyl or glueing sheet-to-sheet you need to use rock-to-rock screws or double hi-low screws. Regular sheet rock screws have no holding power between 2 sheets of rock.

[Doublehelix]

Originally Posted by jchas

I can't speak to which method is better acousticly, but from a construction perspective, if you're going with the high-compression vinyl or glueing sheet-to-sheet you need to use rock-to-rock screws or double hi-low screws. Regular sheet rock screws have no holding power between 2 sheets of rock.

Second layer of rock needs to be screwed to the studs as well.

[DSD_Mastering]

Here's a couple pictures of my build. ASC dRC-1 & 2
Kinetics Noise control ceiling hangers with cold rolled steel and hat channel.

Regards,
Bruce

[themaidsroom]

it looks like you are doing really well.
i did most of the build for the maid's room
for three years - it was a long and crazy time to be sweaty, very, very, very
far away from music and in the middle not really knowing how
it would ever be done.....
i suppose it is never done.
i am in london now
and when i am back n nyc and i am
going to demolish and build more.......


good luck
be well


- jack

[rockstar_josh]

Originally Posted by Sigma

lows are the worst but i have neighbors [rowhome] low end rumble is less offensive than higher frequencies and i wasn't about to put up 3 layers of drywall..i fig if you are doing the double wall at least change up on density and type drywall

i haven't been in many pro studios where ya can't hear bottom coming out from the walls

will check out you link

my room is covered in acoustic carpet so it has no high end ring..it's not dead just warm

Sigma, where did you get acoustic carpet? I'm assuming it's different than regular carpet - I have three rooms facing a common wall, and the sound coming from the doors builds up along the wall, so I need some kind of wall covering to knock it down. I am hoping to solve it without building a bunch of 8x8 traps, and "acoustic carpet" may do the trick.

It's almost impossible to knock out real low frequencies. For me it would be tough financially - the best I can do is keep the mids and highs controlled, and I did a pretty good job of it. I used double layers of sheetrock on staggered studs. I varied the thicknesses/materials in each layer, and pretty much achieved what I'd hoped to achieve. Once you start adding more layers you're getting diminshed returns, it's not worth it. I'm starting another project in a couple of months and I'd like to try using resilient channel and less sheeting this time, and add some vinyl barrier to the mix.

[grexter]

guys, thanks for replies :)

Bruce (Brown) its not the first time you reply to some of my questions - 1) i appreciate your input and 2) i've been meaning to say, i really like the "look" of your studio. I don't really have to be there to see the quality and the attention to detail you've put into it...

but more bitching about the contractors... example: I told the contractor that i want my floor to be very solid (as in no squeaking at all). He was doing it from scratch: shingles/shims on the conctrete to level it than the 2x3 than 2 layers of plywood... The guy had made me buy 3" Tapcon screws but since he had to shim 1.5 " , they never even touched the concrete so instead of telling me about it making me buy longer Tapcon screws, he simply decided to just screw the little shingles to the concrete and not the 2x3 (which he just screwed with little floor screws to the shingles) He said the floor will be rock solid for 20 years. Its been a week and it already squeaks exactly in the spot I'll be standing with my mic while recording my voiceovers. I know maybe i'm a litttle too detail minded but... its driving me nuts

so now i'll probably have to pay another guy to cut off part of the floor (as there are already 2 wall partitions on it) and screw off everything and redo/repair the whole damn thing from scratch.

I've never been a handyman, in fact I've always hated tools etc.. but let me tell you this: 2 weeks into this "shit" (sorry for vulgar words) I've already bought a drill and a miter saw of my own cuz i can't stand the fact some contractors are botching every piece of my room.

[DSD_Mastering]

Originally Posted by grexter

guys, thanks for replies :)
Bruce (Brown) its not the first time you reply to some of my questions - 1) i appreciate your input and 2) i've been meaning to say, i really like the "look" of your studio. I don't really have to be there to see the quality and the attention to detail you've put into it...
.

Thanks... I was fortunate to find contractors that were part-time musicians and actually studied/knew about decoupling and acoustics. What they didn't understand on the drawing, they called the designer immediately. They actually had to do only 1 thing over. They framed up a wall without putting the kinetics blocks under the sills. That was it.
It's in the details man.... I feel for you!

[tifftunes]

Ha! After reading a few of these threads, I feel like I should just give up!

After 18 months or so of studying and planning, I began my small, one room project... I'm doing everything myself except the framing, which I also worked on. But since I had no experience framing, I thought it'd be prudent to hire a pro. And as it turned out, he is my friend's uncle, a carpenter by trade, and did quite a bit of work on my friend's studio. So I thought I was ahead of the curve, so-to-speak. However, he built a couple of walls that comply technically with the "room within a room" concept, which didn't follow my requested "decoupling" plan. Due to lack of funds, time, availability, etc, blah, blah, blah, I decided to let it go.

My "finished" garage already had resilliant channel for the ceiling's primary layer of fire-code 5/8" drywall before we even began! But we added another layer, and no doubt hit joists with the 2.5" screws. I also added another layer of drywall to the existing layer on the walls, THEN built my room within a room. So I have 4 layers of drywall in any given direction from the interior of the studio to the outside world... I hope that's enough to keep bass n drums in, lawnmowers, helicopters and planes out. Keeping fingers crossed...

[Bob Olhsson]

Something that works great is putting sound insulating board (that's usually used against the studs with thin sheet rock) in between two layers of 5/8". It deadens the 5/8" to the point that screws and channel isolation doesn't add that much over just nailing it up and sealing the nails and seams with acoustical sealant.