Rated wall assembly

[BayPointArchitect]

Applicable code: 2009 IBC

I'm looking at a one-hour rated exterior bearing wall for Type VA construction in accordance with Table 601.

The architect refers to Table 721.6.2(2) which gives a value of 20 minutes for a 2x6 stud wall, 16 inches o.c.

The architect refers to Table 721.2.1.4(2) which give a value of 40 minutes for 5/8 inch Type "X" gyp.bd.

The wall section and written description does not make it clear what the exterior sheathing and siding will be.

The cumulative total for the combination of two materials is (20 + 40) = 60 minutes.

The architect also refers to GA File No. WP 8105 which calls for some type of gypsum product on the exterior side of the wall as well as the inside (i.e., DensGlass). I would say that what is illustrated is "similar" to the Gypsum Design Manual but architect is calling for "exterior sheathing" in lieu of the prescribed "gypsum board".

Question:

If this is a legitamate method for calculating a one hour rated wall, then why have I not seen this before?

 

[brudgers]

So long as the wall does not need to be rated for fire exposure on the exterior side, yes.

That's exactly how it works.

 

[BayPointArchitect]

Ben,

Consider yourself having earned 127 thanks.

Have a happy Easter!

 

[steveray]

FYI.....I also believe that ALL penetrations (window and door RO's) get wrapped with that same gypsum in VA construction....if you weren't aware or hadn't seen it yet...

 

[Big Mac]

WOW, Brudgers. Two times in two posts. What is this world comming to?