I’m renovating a kitchen and pwder room, The subfloor is old tounge and groove planking, with a couple of layers sheatflooring on top. The mud room powdr room area is an old porch closed in. The floor there is that old tounge groove you see on a lot of old porches, and still has pitch top it. I need to level the porch area and tile both rooms which are connected by a 4″ wide doorway. Should I cut the flooring up add 3/4″ ply, add backer board and use leveler in porch area.  Looking for some ideas!