[I did this work the weekend before Thanksgiving]
I did the lofts over a weekend. This was scary because I had to work around any bad weather. Until I get the rafters up, a tarp will not protect the lofts. The reason is the same as to why the bottom floor got ruined. The middle will fill up with water. With nowhere to go, it will get heavier and heavier until it shreds the tarp and soaks everything.
Things went VERY quickly. I was amazed at how much progress I made in just a few days. No rain yet.