2' x 13 foot area to retile. I have removed most of the old tiles - all that were too high. This part is down to the concrete bed. The remaining tiles are low enough and sound enough that I hope I can tile over them after leveling up the floor and using DITRA (membrane). To bring the height level should I use self-levelling mortar or regular mortar? 1" maximum depth. Will the membrane take care of any movement/cracks due to the difference in material under the leveling mortar?