Question: How do you protect the subfloor during construction to avoid damage from rain and snow?
Answer: When we build an addition we use ¾” tongue and groove plywood and we seal it with a water seal product. We have tried to cover it with felt paper and visqueen, but it would always leak and then capture the moisture. With the water seal it prevents much of the absorption and lets the subfloor dry out and breathe so it resists moisture damage and mold. This is not a perfect solution but the best we have found.