If the deck is built correctly, you'll have no issue with the weight.I am building a deck all treated. Using. 2 x 10 x 16 as beams and joist with 12 ft span deck is 16.x 16 with 3 6 x 6 under each beam for supports. Would using 6 x 6 for the hand railing post be to much weight if I have them every four foot around the perimeter???