Wood Flooring: What is “underlayment?”
Underlayment refers to the material placed between the subfloor and new floor.
It serves many purposes depending on the quality of the material. The primary purpose is to provide a moisture barrier. Some underlayments can also provide an acoustical barrier to make the new floor quieter when walked on especially in multi-level homes. Underlayment should be used with every floor, and always according to the manufacturer’s installation instructions.