You need to add a new "asset" for the new building. You will keep the old "asset" (your house) and if you stopped using it as a rental, you will tell the program you converted it to personal use. DON'T just add the new building information to the old "asset" for depreciation.
As Carl pointed out, you will need to keep track of the depreciation that you were eligible to take on your old building (your home) for whenever you sell it or start using it as a rental (or business) again.
