I am just starting to plan a basement bathroom. The plumbing for the drains (shower, sink, toilet) was already installed when the house was built. The basement floor has already had two coats of epoxy and a coat of polyurethane on it. I plan on building up the floor and shower area with a mortar bed (with screed) to level things out and to raise the floor for a good fit of the toilet to the flange. My question is: Should I remove the epoxy/urethane coating before applying the mortar bed and if so, how do I remove it?