We used the same subfloor sheathing on the roof that we did on the floor. (We use it as a walking deck.) On the walls we put 1/2 in. OSB sheathing. We then wrapped the house in tar paper because we got a great deal on a load of wet 1x6 fir that we're using on the interior. Later we'll use the rest as vertical board & batt siding on the outside. You could also use shingles or a combination of lap siding and shingles.
5010 S. Inglewood Dr.
Langley, WA 98260