Most finished floors are applied over a well-prepared subsurface. This is especially important for vinyl flooring, as well as for ceramic tile and carpeting. A subfloor must be smooth, level, and strong, or the finished floor will be spongy, sagging, and prone to uneven wear and damage.
The subfloor must also be constructed with the correct materials, fasteners, and sealant for the type of room and the existing construction in the building. The best choice of subflooring is different for bathrooms and kitchens, carpeted rooms and bare wood floors, wood framing and concrete slabs. Using the correct type of subfloor for the desired finished floor is vital for a quality finished job.