What is Underlayment?

Definition of Underlayment in Construction

Any material used as a substrate to a finish floor, finish wall panel, or a finished surface product. Underlayment is used to strengthen the final finish surface, or provide the correct adhesion surface for adhesive used to install the final surface material. Underlayment can also be used as a slip sheet if the material is designed to not adhere to the base layer of the floor or siding. In addition, underlayment of certain types is used to reduce cracking of the final surface, or provide a waterproof membrane beneath a finish surface. Underlayment is a universal, general term for a material, usually sheet products , under a finish surface.