Plywood Structural Sheathing at Roof in High Snow Area

[NewbieStruct]

We are designing a residential building in a heavy snow area. The maximum load on the roof (snow+drift+dead) is about 150 psf. Per the IBC, tables 2304.7(3) and 2304.7(4) the maximum load I see is 100 psf (table 2304.7(3)) for 3/4" sheathing.
Is plywood not possible for the loads?

I am attaching an APA rated span and load table 1b (page 3) that shows that if we use structural I sheathing with a 48/24 rating (thickness of 23/32, 3/4" or 7/8" per the IBC tables) we have capacities of 469 psf and 285 psf in bending (3 span condition) for strength axis perpendicular and parallel to supports for trusses at 16" o.c. If I reduce them down per adjustment table 5 in the attachment to a 1 span condition, the loads are still below our required loads. Is it ok to use these tables?

Another question, I have is regarding the fasteners for 3/4" sheathing for diaphragm capacity. The IBC does not have any tables for 3/4" sheathing. Is there a particular fastener that is used in these conditions? What tables/design do I need to follow to account for the 3/4" sheathing.

 

[JAE]

Two layers gets you double the capacity. More labor and cost there but that is an option - perhaps (2) 5/8" layers?

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[jayrod12]

If you need the 3/4" ply for gravity loads but the numbers for 5/8" ply work for lateral then I would just provide the nailing spec for the 5/8" and be done with it.

 

[Ron]

When using JAE's alternative, don't forget to increase the fastener length on the second layer. Theoretically not necessary, but adds to capacity and doesn't cost a bunch.

 

[Triangled]

I'd suggest that you contact the APA-EWS American Plywood Association help desk. They routinely coordinate with the building code people. They will be able to give you an exact answer on both questions. They are quite helpful. Almost certainly you can use the tables referenced in your case and they can discuss the nailing question at length.

 

[XR250]

be careful assuming you will get a 3 span or even a 2 span condition in the field