On Oct 31, 10:30 pm, wrote:
I've searched around and checked where I could think of in the NEC. Are
there any particular requirements for the size/composition for
crawlspace running boards? I'm rewiring my entire house (built in
1940s, rewired by a previous owner - its a NIGHTMARE!)
I've seen recommendations to use 2x4s. Is this a requirement, or
preference? What about using something smaller?

There is no requirement that you even USE "running boards". I assume
you are running cable and not pipe? The only thing the NEC requires is
that the cable be "adequately supported", using staples or clips
"listed" for the application. As a rule, support romex every 4 feet,
and stretch it tight so that there are no sags or loops.

Hope this helps!

Glenn Grundberg
http://www.goalelectrical.com