Originally Posted by pappcam
My 2012 Flagstaff 27BESS Super Lite (same as Rockwood 2702SS) has aluminum joists on 16" centers in my floor. I think the joists are actually above the bottom layer that you can see on the bottom of the trailer. It's the actual frame of the trailer that you're reinforcing which of course is probably a good thing considering how lightweight trailers are made nowadays.
I think the addition of the extra joists on 16 inch centers was only introduced lately, possibly as late as the 2010 model year, or whenever they did the last major styling change. The OP's is a 2008.