As I have read through several articles here most everything is about homes. I would like some advice on building a butcher shop. It measures 20ft wide x 24ft long with 10ft side walls. I plan to hang animal carcass's from the ceiling rafters on a sliding rail. I want to use a shed type roof expanded over the 20ft width with no center support. I live in an area that gets lots of snow. So my question is- can I do this? Do I need to do something special to the rafter to span 20+ feet? I will be doing all the work myself. I have available to me fresh cut timbers of mostly hardwoods, can I use these timbers in construction like they did in my 1890 built house?