# Staggered metal stud sound wall-2 hour rated??



## liarchitect (Jul 13, 2011)

I have a new job where i am coming in as the relief pitcher bottom of the 9th, no outs, bases loaded and the star player at bat.

The contractor who was fired as well as the non-licensed architect created a sound wall out of the following materials

-6" bottom and top track

-staggered 4" studs on either side at 16" o.c.

-(2) layers of 5/8" type "x" sheet rock"

they thought that the 2 layers is what gave them the 2 hour rating, i had to explain to them that it is the entire assembly that is rated

I can not find anywhere the ul rating for such a wall that is a min. of two hours

can someone point me in the right direction to find this information?

thank you in advance


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## Examiner (Jul 13, 2011)

You can do an equivalency rating for the wall's composition from Chapter 7 [iBC 2006 Section 721].  You do not have to quote UL numbers every time.  Yes two layers of Type X sheetrock will give the wall a 2-hour rating.  A 2-hour wall using metal studs can go down to 1 5/8” studs.  Staggering studs is okay as long as the spacing on each side complies with the spacing for any other rated stud wall.  Usually 24” max oc.  Look for chase wall types in the UL, USG or other sheetrock manufacturers listings of rated assemblies.


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## liarchitect (Jul 13, 2011)

thank you for the quick reply


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## brudgers (Jul 13, 2011)

liarchitect said:
			
		

> non-licensed architect


No such thing.


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## hlfireinspector (Jul 13, 2011)

The one hour version is UL U340 in 2000 directory

Sorry wood studs


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## mtlogcabin (Jul 13, 2011)

The GA manual has a 2 hour wood stud wall at 16" OC stud spacing (3910) but not metal studs

http://www.gypsum.org/pdf/GA-600-09_Print_7_Megs_part1.html


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## Mark K (Jul 13, 2011)

Many metal stud walls need to have bridging or straps at mid height in order to resist out oo plane loads.  How would you install the bridging if the metal studs are staggered?


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## alora (Jul 13, 2011)

Mark K said:
			
		

> Many metal stud walls need to have bridging or straps at mid height in order to resist out oo plane loads.  How would you install the bridging if the metal studs are staggered?


No different.

Especially if using clip angles & channel bridging.


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## Mark K (Jul 13, 2011)

With staggarged  metal studs with 2x4 studs on a 6 inch track it is not clear that the prepunched holes in the studs will allow you locate the channel bridging without conflicting with the other offset studs.


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## AegisFPE (Jul 13, 2011)

> You can do an equivalency rating for the wall's composition from Chapter 7 [iBC 2006 Section 721]. You do not have to quote UL numbers every time. Yes two layers of Type X sheetrock will give the wall a 2-hour rating.


The calculated method of fire-resistance in IBC 721 is limited to a maximum of 1 hour on wood studs (721.6.1.1)!

Looks like GA File No. 5060 or 5071 may be consistent with the subject assembly, though each is a proprietary system.


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## alora (Jul 13, 2011)

Mark K said:
			
		

> ... it is not clear that the prepunched holes in the studs will allow you locate the channel bridging without conflicting with the other offset studs.


They won't.

The bridging's not expected to go through every stud.


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## Papio Bldg Dept (Jul 14, 2011)

brudgers said:
			
		

> No such thing.


information architects and custodial engineers are typically the bain of the licensed A/E world, and usually only carry a driver license at best...but yes, there should be no such thing as a non-licensed architect.  without a license you are not a professional architect or engineer.  me thinks some laws might have been broken somewhere, somehow on this one.

did they stagger the drywall?  was there a screw and tape inspection for the first layers?  lots of unknowns if already built.


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