With space being such a limited commodity for me I have learned to plan carefully. I do not store any sheet goods other than decent sized drops frpm completed jobs. When I am ready for sheet goods, I go get them. Solid stock is another matter. I buy my Oak in 600 bdft lots because that is what my F150 will carry comfortably, and I can get that amount planed to thickness over a weekend. This I stack outside under a black tarp, elevated about 14" off the ground. Been doing it like this for years with no problem. My shop space I reserve for tools and assembly.