The subfloor serves as a platform for flooring materials. Wood sill plates sit on top of the foundation walls, upon which floor joists run. On top of this is a plywood deck. The finished subfloor can now hold the flooring material of your choice.
Flexible flooring materials for a foundation subfloor include laminate, carpet, vinyl and various hardwoods. Basement Questions also lists bamboo as an attractive choice because of its resistance to stains and moisture, ease of cleaning and renewability. These materials have a certain amount of “give” that allows them to flex without cracking.
Relatively dense, rigid flooring materials such as tile and stone require special reinforcement of the subfloor structure. Unlike building materials that can flex, tile may crack when the floor shrinks or expands. To guard against this kind of damage, Small House Building recommends installing decking material made of heavy, rigid plywood, followed by a cement backing board. This reinforcement adds considerably to the weight of the entire subfloor, so the joists should be able to support it. The flooring materials you wish to use will have a major impact on the subfloor’s structural needs, so discuss these matters with your builder during the planning stage.
If your foundation consists of a solid concrete slab, your options for flooring are wide open. Note that most hardwood and laminate flooring require a moisture barrier when installed over concrete.