Building a frame to make a concrete floor. step 2 with the area cleared out we could now build a foundation frame for the concrete floor. with mother nature not on our side, we headed to home depot to gather supplies and shed material.. to build the frame we started with 2 x 4 pieces of wood.. To speed up the assembly process, build all the trusses on the shed floor before erecting the walls. start by cutting all the rafters to length with a 40