Ring Shank Nail Withdrawl Loads Roof Sheathing & Diaphragm - NDS verse FBC

[eng003]

The florida residential building code (and maybe the IRC?) presriptively requires 8d ring shank nails for roof sheathing attachment I have the following questions regarding their use:
1. What are their withdrawl loads? NDS doesn't seem to address unless it is appropriate to use the threaded nail values?
2. How does the diameter of a ring shank nail compare to common?
3. How does one reconcile the fact that NDS diaphragm capacities are for common nails? If necessary can you adjust the values for ring shank nails?
4. In evaluating required nail spacing for withdrawl does one need to consider simulatneous shear forces as part of of a roof diaphragm action?

 

[LonnieP]

Eng003 - - We used to specify Annular Ring (ring shank) Nails for withdrawal applications (ceiling stripping) but changed over to Spiral Shank Nails. We changed because the Annular Rings shread the wood grain in the immediate area around the nail and the Spiral Nails don't. It's not such a great problem in areas with high moisture, like Florida. In the desert areas of Southern California the wood drys out and the ring shanks loose their increased withdrawal resistance. The wetter the wood at time of driving the nail, the worse the capacity loss for the Annular Ring nails.

That said, I'd go with what the local building department wants unless they say you can use Spiral Shanks instead. I think Spiral Shank nails are commonly used for roof nailing in the mid-west USA (tornado country). They are not all that expensive and come in clips and rolls for most nail guns. Check with the manufacturers for withdrawal values because spiral pitch and shank shape may vary slightly between manufacturers.

LonnieP