Depends on the condition of the slab and if it has any issues.
Ditra mat over concrete.
While ditra is my preferred membrane for floor tile installation as well as countertops and tub decks it absolutely needs to be installed correctly.
Ditra is 1 8 3 mm thick which minimizes tile assembly thickness and reduces transitions to lower surface coverings e g carpet engineered wood and vinyl.
Ditra over concrete floors.
Schluter says this is ok.
The combination of these four essential functions allows for the successful installation of tile over a wide range of substrates including plywood osb concrete gypsum heated floors etc.
The two main techniques for this are fairly simple.
If it s newer and has cracks i wouldn t use ditra.
Install it over an approved substrate and with the correct type of thinset mortar.
Select ditra or ditra xl underlayment depending on the.
Don t install tile the same day over the ditra heat mat.
Please consult the schluter ditra installation handbook before beginning your tile project to confirm the proper materials selection.
Ditra heat tb has additional insulation for going over concrete floors.
Purchase a suitable trowel for the thin set mortar between the substrate and the ditra membrane.
Make sure the cavities waffles are filled correctly.
Again i think this is a bad idea.
If it damp ditra would be my choice.
To set ditra over concrete or gypsum schluter systems recommends an unmodified thin set mortar meeting the requirements of ansi a118 1.
The type of thin set mortar used to install ditra depends on the substrate material.