Installing Type NM Cables in Unfinished Spaces

Where Type NM cable is run at angles with joists in unfinished basements and crawl spaces, it is permissible to secure cables not smaller than _____ conductors directly to the lower edges of the joist.

a) two 6 AWG
b) three 8 AWG
c) three 10 AWG
d) a or b

See answer and applicable Code reference

The correct answer is: d) a or b

The installation requirements for nonmetallic-sheathed cable (Types NM, NMC and NMS) can be found in Article 334 of the 2011 NEC. As outlined in a portion of 334.15(C), "Where cable is run at angles with joists in unfinished basements or crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists."