There are many obvious considerations here, I'll let others address those. I just want to mention one thing that's often overlooked: the legal aspect. you have to comply with bldg codes, local ordinances, mfg instructions, AND inform your insurance company. failure to do any of these can possibly void your fire insurance, which in turn may even create a breach of contract with a lender. I had it happen. Ain't as simple as it used to be, that's for sure.