[carpdad]

Flooring needs expansion space, all sides. Depends on the flooring but I just try to remember 3/8. Also the edges are covered by molding. If using quarter rounds as well, a lot can be covered. Door jamb and trims are cut and it's easier if you cut some of the drywall so the flooring can easily fit under the jamb/trim - under the drywall. So if you have 1/2", you can use full widths.