Tiling where old tile was installed with mastic
I've had the old tile removed in my entryway/hallways. It was 4" ceramic tile that was installed with something like mastic. After popping off the old tile, quite a bit of mastic is stuck to the plywood subfloor.
I had been planning to install the new porcelain tile over Ditra. Will that be okay with the remnant mastic there? If not, how best to handle it? Would it be better to install hardibacker, bedded in thinset over the mastic/subfloor?