Steel Studs---16" or 24" OC

MArk Scheuerman · Post by **MArk Scheuerman** » Sat Apr 05, 2003 3:14 am

I have about a 20' x 20' x about 7' tall area of my basement I am planning on converting to a studio. I have seen where using steel studs will give you a better STC rating than wood & I have found steel studs cheaper than wood. Which stud spacing would be better 24" or 16" OC? I'll probably use double wall constructoin between the control room & live room as follows: control room - steel studs w/fiberglass insulation - 5/8" sheetrock - soundboard - 1/2" sheetrock - air gap - 1/2" sheetrock - soundboard - 5/8" sheetrock - steel studs w/fiberglass insulation live room. Or would it be better to have the sheetrock & soundboard on the room side of the studs, or sheetrock on both sides of the studs? I will be doing room treatments & angle the walls so opposing walls are not parallel. I have started some drawings in smart draw & will probably post on the design forum soon. Do you think the room height restiction will cause many major problems?

knightfly · Post by **knightfly** » Mon Apr 07, 2003 6:01 pm

To partly answer your question on wall construction, check out this thread

http://www.homer.com.au/phpBB2/viewtopic.php?t=86

Specifically John's post of Mar 01, showing STC ratings, and my comments on Mar 17 regarding WHY the different constructions changed the STC ratings. Note in particular, that both the STC 40 and STC 63 walls use EXACTLY the same quantity of materials, yet one is 23 dB BETTER...

In the case of metal studs, it is my belief (unfounded due to lack of testing) that metal studs used in separate dual wall construction such as the STC 63 wall won't make quite as much of a difference over wood as they do in a single stud partition, such as the chart's STC 33 and STC36 examples.

My reasoning is this: the main reason (as you apparently already know) that metal studs outperform wood is their flexibility, giving the two leaves of the wall better de-coupling. In the case of two SEPARATE walls with covering only on the outer side of each frame, the two leaves of the wall are decoupled by air, which, although it is a spring, would be less rigid than the stud. (Still, after reading some in US Gypsum's handbooks I think having Resilient Channel under one of the leaves wouldn't hurt, and might gain 2-3 dB of STC.)

On the 16" vs. 24" question - different spacing would change the stiffness of the wall, which would also change the resonant frequency of the wall. If both sides of the wall resonate at the same frequency, that frequency will pass thru the wall easier which is not good. That may be part of why US Gypsum recommends when using Resilient Channel that you put it on 16" centers when mounting on 24" studs, and vice versa. (Although, I think the main reason for that is just having similar support capability)

I have nothing other than gut feel to back this up, but I think I'd do the double wall between the CR and Tracking rooms like the STC 63, perhaps with the variation of materials you mention, and vary it even further by putting the metal studs with NO Resilient Channel on 16" centers, then put the studs WITH the RC on 24" centers, mounting the RC itself on 16" centers.

That way, you have more RC's to support the multiple layers of wallboard. If you went with ALL sheetrock over the RC, I'd tighten up the spacing of the RC to 12" with three layers.

If I were doing this, I'd also make one of the leaves a different mass/sq foot by using TWO layers of 5/8" rock with soundboard in between on one side. - This will broaden the resonance of the wall so there is less likelihood of one particular frequency getting through.

Remember, separate walls have to maintain their separateness - anywhere they need to touch, it should be with some type of isolator such as the type made by Kinetics Corp and others. Following this idea, you cannot have a common window sill for separate glasses - see the SAE site -

http://www.saecollege.de/reference_material/index.html

Click on Construction, then on the tab for Windows/doors, scroll down -

Also, when planning walls with this high performance, remember there are lots of other things to plan for, so as not to waste the effort. STC 60 walls are pointless if your doors don't seal or you put electrical boxes back-to-back in the wall, etc...

The low ceiling isn't the best, but it's what you're stuck with - if possible, I'd put at least 2" 703 "clouds" over the mix position, and for at least part of the live area. Also, I hope your layout gets rid of the equal length parallel walls, unless you really like songs with lots of 28 hZ, 56 hZ, 84 hZ, etc... Steve

Michael Jones · Post by **Michael Jones** » Wed Apr 09, 2003 12:37 pm

You should probably check with your local building department too.
But In general 16" centers are required for load bearing walls, and 24" spacing can be used for non-load bearing walls. Both wall systems require different minimum sheathing as well. 1/2" for 16" centers and 5/8" for 24" centers.

Again this is very general and it would be wise to check with your local building department.

nukmusic · Post by **nukmusic** » Wed Apr 23, 2003 1:13 am

sorry to step in, but on the 16 or 24 oc walls..................like the basement, I have a 20 x 20 x 10 garage. I'm think I may be able to use 24" spacing because I,m just building a box inside of a box with no load to hold from the ceiling. It's a 1 story newly constructed brick home. Can I do this???

knightfly · Post by **knightfly** » Wed Apr 23, 2003 6:02 am

Most likely it will be OK, but as Michael pointed out, it's best to check with your LOCAL building codes department. When you talk to them, get the person's name and job title and take notes. That way, if there is a disagreement later, you at least can say, "But Johhny said..." Steve

nukmusic · Post by **nukmusic** » Fri Jun 20, 2003 6:22 am

What guage metal to use for non-load bearing walls?
I have seen 14, 16, & 20 gauge. I may consider using metal, because last time I checked the prices were about the same as wood, I Think

knightfly · Post by **knightfly** » Fri Jun 20, 2003 9:52 am

USG only mentions 20,22, and 25 ga studs - I've not even seen anything as heavy as 14 ga, those would be pretty expensive. Not to mention losing some of the flex that makes the steel better for sound proofing.

I've not built steel stud walls yet, but from the ones I've seen I'd say 20 ga would be a good weight for a non-load bearing wall. You need to do everything right with steel or you'll have problems - in case you've not seen it, here are USG's two best resources on the subject -

http://www.usgaction.com/handbook/toc.htm

http://www.usg.com/Design_Solutions/2_3 ... ontent.asp

Gotta wade through a fair amount of stuff, but there's some really good info there... Steve

nukmusic · Post by **nukmusic** » Fri Jun 20, 2003 1:12 pm

cool......I man a few phone calls today and got a few quotes. And you're right like always, because the sales rep recommended 20 gauge, and the 14 &16 gauge was higher in price. 20 gauge was .35 cent per lin. ft .

knightfly · Post by **knightfly** » Fri Jun 20, 2003 1:19 pm

"And you're right like always" -

That's the way it is when I'm tellin' the story too - "course, that doesn't apply when my wife's in the room :=)

khallgren · Post by **khallgren** » Sat Jun 21, 2003 4:06 am

This thread has brought up all kinds of questions for me.

How much drywall can you hang on steel studs 24" OC? 1, 2, 3 layers of 5/8" drywall?

What about when you add resilient channel?

I've heard it's better to have studs spaced wider than narrower, but there are a lot of questions for me here. What's better--16" oc studs and 3 layers of 5/8 or 24" oc studs and 2 layers?

How much drywall can be safely hung on 16" oc studs with 24" oc resilient channel?

I think I may be going crazy. I'm ready to convert my garage into a practice room but want to make sure I'm utilizing my materials in the best way possible. Anybody have suggestions?

knightfly · Post by **knightfly** » Sun Jun 22, 2003 4:45 pm

khallgren, most of the answers you're looking for are in the two USG links I posted above - the bad news is, it is buried kind of deep and takes a while to sort out. I'll try to answer your questions from memory, but you should check out those two resources for yourself and if I goofed, please don't hesitate to point at me and laugh...:=)

"How much drywall can you hang on steel studs 24" OC? 1, 2, 3 layers of 5/8" drywall?" - This would partially depend on the gauge of the studs, as well as their width. These come in widths from 2-1/2" to 6", and gauges from 25 up to at least 20 gauge. If you use the 20 ga studs 3-5/8" or 4", you should have no problems with two layers of 5/8 drywall on one side, using 24" centers. 16" centers would handle 3 layers, since the studs are 50% closer.

When you add RC, it is recommended to be used at either 16" centers spaced 24", or 24" centers spaced 16". That allows for a single layer of 5/8 rock if I remember correctly. As you increase the loading, you need to both decrease the stud centers AND decrease the distance between the RC - Generally, you would tighten the spacing of the RC from 24" to 16" to add a second layer, and from 16" to 12" to add a third layer. If you're planning 3 layers of sheet rock on only one side of a wall, I would definitely use 16" stud centers, and probably 12" RC centers.

Keep in mind that, depending on your isolation needs and what the REST of the construction is like, that you may be wasting time/money/materials going that far. Few doors can keep up with a 2-panel-per-side, properly built wall, much less a triple-layer 2-leaf wall.

The other thing is, the third layer of sheet rock doesn't seem to add as much as the second one, and you would be almost as good using 2-layers each side but spacing the wall frames further apart (if it's a double-framed wall) it would cost less and be easier to build.

If you're going to build a single-frame wall with RC on one side using steel studs, I think you'd be at least as good using 6" steel studs with RC on one side and only two layers of wallboard. That will get you about 15 dB better performance than any home-built door you can come up with, and the alternative doors run anywhere from $3000 up to $6000 EACH. Those can reach 60 dB or so.

In order for a DIY guy to equal that, he'd have to build a serious sound lock/double exterior door/drop seal setup. I'm planning to do just that in my new facility in a year or two, but then, I'm an anal idiot with loud lawn-mowing, dog barking neighbors and I like plaintive acoustic guitar/flute things sometimes, in between thrashing acoustic drum kits within an inch of their tension-filled little lives...

One of the main things you should do if you need serious isolation from neighbors (both ways) is to find a local source of REAL acoustic caulk/sealant, usually from a commercial insulation/drywall contractor. If you can't find that, I've posted a link here somewhere to the stuff (at about twice the price you'll pay locally)

If you haven't gone to the USG sites and read through those two guides, you owe it to yourself to do so - give yourself quite a bit of time, they're pretty comprenensive... Steve

khallgren · Post by **khallgren** » Tue Jun 24, 2003 1:39 am

Steve-- Thanks for the reply.

I've already ordered, paid for, and received the materials for my 26'x22' garage-conversion-into-a-studio project. My plan is to finish the existing walls/ceiling and then frame and finish the interior room. I've got enough drywall to do 4 layers. I was considering doing one layer on the outer wall and 3 on the inner, but your reply seems to suggest two on each would be better. I'm avoiding a 3-leaf wall by cutting the drywall on the outer wall to fit between the existing studs, since I don't want to totally re-build the garage. Any thoughts on this from anyone?

The steel studs are 25 ga and 1.5 x 3.5 which will be used for framing the inner room. I'm not as worried about insulation around the door because the door leads to my single car garage which is remaining intact. Leakage through the door leads only to my other garage, not outside. I've really only got to isolate the other three walls and the ceiling.

I've been waffling about the resilient channel--I've heard conflicting remarks regarding its use with steel stud construction with some saying it's not necessary due to the inherent resiliency of the steel studs.

I've got 52 tubes of sheetrock brand acoustical sealant. Linked to here: http://www.usg.com/Product_Index/_produ ... GreenLink=

This stuff was $3.36 for a 29 oz. tube from a building materials supplier in Detroit, MI (a 30 minute drive for me) vs. the $7.50 (plus shipping) of some stuff I've seen recommended before (http://www.acousticalsolutions.com/prod ... /caulk.asp).

I'm planning on getting more of the sealant, but that's all they had in stock and I was anxious--so I figure I'll use that and then order some more.

One last thing--The existing ceiling is 26x22 with 2x4 lumber at 24" oc. Can I safely suspend 2 layers of 5/8 sheetrock on this?

I know my questions betray my ignorance, but I figure it's better to ask BEFORE the ceiling falls in on me (at which point I wouldn't have to ask, I suppose...).

Anyways, thanks to everyone who has made this site such a valuable resource.

xoxo

Kraig

knightfly · Post by **knightfly** » Wed Jun 25, 2003 6:36 pm

Kraig, first on placing the sheet rock between studs and up against the outer wall sheath, that's about the only way I know of that you can get some extra mass in the outer leaf of the wall. If you use the lighter steel studs for the inner wall frame, the RC isn't as necessary. It might contribute a couple of dB as far as STC is concerned, but you might lose it as far as MTC is concerned - I still need to get this clarified more by Eric if he gets a chance.

The door leakage you refer to might actually HELP you, in the form of some extra bass trapping into the garage.

I know what you mean on the cost of caulk - I try to mention that if you can find it locally it's lots cheaper. I'm glad you're using the real stuff though.

As to the double layer of 5/8 sheet rock on your ceiling joists, I'm not quite sure on that. My span calculator didn't migrate to the new laptop under XP, and the old one isn't with me at the moment. I'm going to assume (since it would have ALREADY fallen on your head otherwise) that those 2x4's are part of roof trusses - if that's the case, it would partially depend on how the trusses are designed.

Generally, trusses are designed to support the ceiling material AND the roof covering, with enough margin of safety to handle at least a medium snow load (in areas that are likely to need it) - The extra layer of sheet rock would amount to just under 2 psf extra load, and typical roof ratings run anywhere from 10 to 30 psf so it's possible you would get away with it.

Bottom line, though, is you should check with an architectural engineer before you take the chance... Steve

Eric_Desart · Post by **Eric_Desart** » Wed Jun 25, 2003 8:43 pm

knightfly wrote:If you use the lighter steel studs for the inner wall frame, the RC isn't as necessary. It might contribute a couple of dB as far as STC is concerned, but you might lose it as far as MTC is concerned - I still need to get this clarified more by Eric if he gets a chance.
Steve

This is a lot of stuff.
Maybe later, but your summary is Ok.

RC is a spring.
RC starts decoupling at ca 2 times the spring resonance (see also other decoupling picture I once entered - it all works the same)
So the decoupling increases in function of rizing frequency.
This indeed can improve STC, but STC is an irrealistic weigthing for every day noises, and CERTAINLY for music.
Getting the feel for my acoustic selector file allows you to check the impact (All Boral + Pac walls).
Here in Belgium and in huge parts of Europe one hardly can find RC. RC is mainly to be found in countries where for whatever reason, wood is a more common building product in the professional building world.

The problem is finding enough data to do responsible analysis. Whatever you find is mostly related to STC hardly interesting for the studio world.

Basically the stiffer a panel becomes the better for low frequencies, since the long bendingwaves for the low frequencies get mechanically surpressed.
However Mass-Spring-Mass in itself is also a spring. This is the most powerful phenomenon.

More systematically in the future.
Just a general axioma. An office grade drywall with metal studs should become worse when one should be theoretically able to perfect decouple those drywall leaves. They become good as they are BY the metal studs.
Those metalstuds damp the Mass-Spring-Mass effect of the wall and damp the long bending waves in the drywall itself.

Best regards
Eric.

mpr3 · Post by **mpr3** » Mon Jun 30, 2003 8:45 pm

Speaking of multi-layer drywall: how would you fasten the second layer of drywall on a ceiling?

I know for the walls you can use builders glue to fasten the 2nd layer to the first drywall layer that rests on the RC, but the ceiling seems like it would need screws through the first layer and into the RC. Is this right?

I guess if you had patience you could set the drywall machine to hold each drywall panel in place, go have a beer... then repeat on a new section. I know the drywall guy will know what is best, but I wanna know now!