It's been a week since the 5 day Tiny House build event has concluded and I finally have some time to start working on it myself. Thanks to everyone who came to the workshop and helped get it this far. For those of you who had to leave early, we were able to get all of the rafters up and most of the wall sheeting in place. I started on the roof sheeting. I started by deciding to use 1x6 tongue and groove pine for the edges of the roof that are exposed from underneath. The issue I noticed in doing this was that the roof sheeting (4x8-1/2 CDX) plywood, is 1/4" thinner than the 1x6 T&G pine boards. Even though the roof metal that I eventually put on will probably make it so you can't see the small drop in thickness, I'm planning on putting some extra roofing felt on the CDX just to bring it a little closer to the thickness of the 1X6 T&G.
I suppose you don't necessarily have to use a different material in the "exposed" area, but I had the product on hand and it looks better than just the CDX plywood showing underneath. By the way, in CDX grade plywood, the C & D means that one side is a better grade than the other and the X means it's got an exterior glue so it won't delaminate if it gets rained on a couple of times. I'm thinking that if you wanted to just let the plywood be your finish under the overhangs and under the front porch, you might consider installing the plywood with the better "C" grade facing down. It is normally installed with the better grade facing up.
The next thing I plan to do is get metal roof edge and #30 roofing paper to make it somewhat water tight 'till the metal roof is on. Although we plan on putting in skylights on the roof, for now I'm going to cover it with the roofing paper, but I will need to buy the skylights and frame the roof properly before I can put the metal on the roof.