I am wanting to install ceramic tile in my bathroom. I have removed the old vinyl sheet flooring. There is a layer of backing from the vinyl still adhered to the subfloor. We are planning to install a cement backer board to the subfloor. Do we need to remove the layer of vinyl backing from the subfloor prior to installing the backer board? If so, what is the easiest way to remove the backing? It is very adhered to the subfloor.