prepare for the tile basement bathroom
We are finishing our 1950's poured concrete basement now. The walls and floors are good without cracks. Our basement has no water issue and a French drain/sum pump was added for double protection. Outside ground surface water is also guided away from the house perimeter.
We are thinking install engineered wood floor on the finished basement rooms. But for the bathroom, we are thinking use ceramic tiles or travertine tiles. We are preparing the basement floor with the following composition: plastic sheet + 1" rigid foam + AdvanTech subfloor. Then the engineered wood floor will be put on top of it. Plastic sheet here is to stop moisture from the ground.
I was thinking put the same composition on the bathroom as well. The ceramic tiles or travertine tiles will lay on top of that composition. But my friend thinks it is not necessary to have rigid foam and AdvanTech subfloor on the tile bathroom. He think just put the ceramic tiles or travertine tiles with thinset on the top of the plastic sheet is good enough and tiles will be cold anyway. Is that true? He also suggests use Schluter Ditra or backer board on top of the plastic sheet if I want to.
What's your opinions? no rigid foam and AdvanTech subfloor are necessary? tiles set on top of the plastic sheet will be stable enough?