Question: what are the layers of flooring?
Answer: Joists. Joists are the first, lowest layer of flooring and support everything above. ... 
Subfloor. The subfloor is the next layer above the joists and acts as a foundation for both the underlayment and surface levels of flooring. ... 
Underlayment. ... 
Surface. ... 
Plywood. ... 
Oriented Strand Board. ... 
Particleboard. ... 
Concrete.