CFS roof sheathing?

[SteelPE]

I am in the middle of designing a project that is a single-story bank (think satellite branch to serve customers). When we put the proposal together, we were thinking the project would be 50% wood and 50% steel. No the project is going forward and the architect has informed us that it’s not 50% wood but rather 50% cold formed steel (metal studs). I don’t have much experience with the design of CFS, but the architect said that portion of the project will be designed by the sub with input from me.

The project is IBC 2015 with ASCE7-10. The large spans and fancy bits of the bank will be handled by steel (which we are almost done designing). Smaller spans and less fancy bits including flat roofs and walls will be framed using metal studs. With regards to sheathing of the studs. The architect wants noncombustible construction, so plywood sheathing is out. Currently the architect is showing 1 ½” B roof deck. I think this is overkill, however, we need the diaphragm of the roof to transfer lateral loads.

What is the typical roof sheathing used in this instance?

 

[phamENG]

Yes. I typically spec type B (but in a very light gauge) when working with cold formed steel joists at 16 to 24 centers. Densglass wall sheathing is a good way to go for non-combustable exterior wall sheathing.

 

[SteelPE]

Thinnest we typically spec is 22ga B deck. That is the thinnest we have tables for (at least the ones we have readily available). Seems like an enormous waste to use 22ga deck on roof memebers spaced 16" o.c.

I did find a product called Sure-Board that offers a noncombustible sheathing with shear resistance. I have forwarded the information to the architect to see what he things. I am guessing we are going to be sticking with B deck.

 

[phamENG]

I've never seen this before - looks like the Steel Deck Institute just published it at the end of 2017 - but seems well suited to your situation. "Steel Deck on Cold-Formed Steel Framing Design Manual." It's free to download from SDI if you want to give them your info. Seems like a good addition to my library, so I gave them my info. Hope it helps.

 

[phamENG]

And if you want load tables, you can either buy the SDI Roof Deck design manual for generic profiles and minimum capacities required to be achieved by member manufacturers, or you can just use a manufacturer's load table:

Vulcraft Deck (Vulcraft goes down to 24ga)
Lots of others out there if you do some looking around.