By Relocation.com
First check the underlayment for damage. The underlayment is the material that provides a flat level surface for the finished flooring and toilet to rest on.
Replace any damaged sections by cutting away the underlayment. A circular saw works well for this job. Replace the damaged piece with a new piece of material with the same thickness. If you are installing a new floor over an existing one, plan to get an extension flange that raises up to align with the flooring height.