I have a 20'x25' detached garage I had thought about raising the roof & adding a second floor. The existing attic/roof is trusses spaced 16" and the garage walls are 16" spaced wood studs. My question is this... What kind of nightmare would it be to add living space? I would think the 1st floor walls would support a second floor but might there be foundation issues with the additional weight? I know I need to get a contractor out for definitive answers but if anybody has experience in this type of thing and can tell me some things to look out for I would appreciate it.

Wife backed into our wood 16'x7' door. Damaged lower right corner, knocked 3 rollers out of rail. Bottom frame board cracked at joint - 3' foot piece that connects to the stee cable is now loose. Lower panel also loose. I want to repair this door. I'm planning on removing the full bottom section by removing the 2 steel cables, removing the hinges that connect the lower panel to the rest of the garage door and then move the bottom panel to the floor, leaving the rest of the door hanging from the rails. I plan to use metal splices to re-join the bottom board that separated at one of the finger joints. (I'll use metal splices - like those used in russes - to repair any other braken frame boards. I'll re-insert the panels as best as possible without messing with the trim any more than needed. Is this feasible - especially removing the full 16' bottom section to repair is and then re-attaching it to the other sections? I plan on removing this lower section with the door fully down, so that the bottom edge of this lower section is rsting its weight on the garage floor. Sound reasonable? Thanks in advance.