I would recommend using a tongue-and-groove pine.
- You can get it "Penta-treated" to guard against insects.This is not the same as pressure-treated, so it is good for covered porches but not for an uncovered exterior porch.
- The wood can be left natural, coated with a clear finish, stained or painted.
Perfect for a rustic home in the woods. Very affordable and easy to install.
For more information:
Read GreenHomeGuide's flooring backgrounder "Navigating the Flooring Thicket: Find the Greenest Way to Meet Your Needs" for more details.