Also, the adjoining area is about 5 inches below the main section which already has live load engineered open web joists, so I needed to build up the area with perpendicular 2x4s to just about a half inch below the adjoining to make room for the subfloor, again with a lot of glue and nailing to reduce any chance of squeaking. The extra space also let's me make room for duct work that I will extend and run down the columns.