This Rafter Design Calculator is for use with a conventional
Rafter/Ridge Board/Ceiling Joist type roof system with thrust being restrained by the ceiling joists.
Adjustments for snow load duration and repetitive member use have been made where applicable.
Table R802.5 of the IRC should be consulted. The code table R802.5.1(9) lists only 16d common nails, this calculator lists several other nail types
Allowable Nail loads are published in the NDS, some examples are below.
Notice that nail strength is based on diameter and specific gravity
Single Shear, 1-1/2" thick sideboard nailed to main member with nails of given diameter.
Nail penetration at least 10 diameters into main member.