Or RMC - especially if the area is misted to moisturize the air. Also, with the dirt floor, AHJ might consider it a damp area. (edited to add, or course, RNC would work too - ask the AHJ)
What kind of structure are you dealing with? Steel posts in concrete footings supporting a open web steel truss roof structure?
[This message has been edited by DougW (edited 07-11-2004).]