Underlayment for hard-surface flooring is a key component in many installations. Depending upon the type of finish flooring under which it is installed, it can quiet impact and ambient sound; improve thermal insulation; smooth out little floor imperfections; help inhibit noise from traveling into the room below; act as a vapor barrier and provide moisture protection that helps keep the finish flooring dry. But that wasn’t always so. Underlayment has come a long way since its introduction as a way of dealing with imperfections in subfloors.
Early resilient flooring (chiefly vinyl asbestos tile and linoleum) was so thick and rigid that imperfections in a plywood subfloor did not show through. As resilient flooring manufacturers reduced the thickness and stiffness of their products and began using patterns, imperfections in the plywood transferred through to the surface became more noticeable, evoking complaints from homeowners.