Underlay is a thin barrier that goes in-between your subfloor and your chosen type of flooring, underlay is a pretty practical home solution. While it sounds like it may not be essential and just an extra step in the tedious installation process, most flooring needs underlay. This layer adds an abundance of thermal insulation to your home as well as blocking out excessive noise. It can also make your installation process easier than working directly from a subfloor. Flooring underlay is a sturdy base which stops your future floor from shifting around.