ok, i thought i posted, but it didnt seem to take.... so ill try again here. 2.5 years ago, we put in a porcelain deck on our rooftop using 18" x 36" tiles and the gratedex system. It cost a lot, but we love it, love it, love it! We tore out a fiberon deck to put this in (mold and installation issues). The tile looks as good as the day it was put in and there is NO maintance. If anyone is interested in this system, Ill be happy to tell you more about my experience (there are some tricks to it) I dont come on this forum often, but you can email me at: brbruzda at hotmail.com. I stressed about our deck for so long and tried to find some direction, i'd be happy to help anyone in the same situation I was in. By the way, we're in Cleveland, so we get the same weather as western Pa.
Best of luck!