hi i am going to build a 28'x16 workshop (shed) but i want to put a timber floor frame in for the floor.i dont want to build a slab.so i was looking at putting 4" pvc tubes in the ground say 2 foot deep then filling them up with concrete for support for the frame would this be ok or could any one tell me the best way to support the shed of the ground without doing a slab thanks alot for reading tom