Underlay

Also known as Carpet Cushion or Padding.

A layer of material that lies between the carpet and floor, which makes a hard backed or felt backed carpet softer underfoot and helps preserve the look whilst providing it with tougher protection against wear and tear.

Underlay under most residential carpet should be a thickness of no greater than 7/16" and no less than 1/4" with 6 pound per cubic feet density. If the carpet is a Berber or a low profile carpet, choose a cushion of no more than 3/8" thickness with 8 pounds of density.