its not explained in the class description..? but dude this can soooo easiliy be answered with testing... create a char, open up a module pick a heavy armor, use a spell... a good module i use for testing is the pretty good character creator
you can google it "nwn vault pretty good character creator" i think thats enough for finding it in the nwn vault(i use the 4.4 beta version)
=)