The thinness and softness of sheet vinyl requires that it be installed on a surface that is very flat and smooth. Installing underlayment in the vinyl areas supplies the elevation, smoothness and levelness necessary for the proper installation of vinyl floors.Particle Board. One common underlayment for vinyl floors is 1/2-inch particle board. It’s inexpensive, flat, smooth and bonds well to the vinyl adhesives.he thinness and softness of sheet vinyl requires that it be installed on a surface that is very flat and smooth. Installing underlayment in the vinyl areas supplies the elevation, smoothness and levelness necessary for the proper installation of vinyl floors.