I have just moved a wall on a storage shed out 6 feet to frame in an exterior attached patio. The size of the storage shed is now 16 x 16. The roof is supported by the outside walls and use 2x4 trusses which span 16' on 24" centers. What size beam will I need, if any, to replace the old wall (the one that was moved out 6 feet) in order to support some small storage in the attic?