prep for tiling over quarries

[bramleyman]

hi,still finding my way round here so forgive if the answer is elsewhere.
i have to prepare floor for new tiling. floor is old quarry tiles, solid with no signs of damp. should they be sealed with epoxy or liquid dpm or something else? dont want to cut any corners. thanks for your replies

 

[Gazzer]

Are you tiling over them? Not the best idea.

 

[bramleyman]

yes ,tiling over . floor is original edwardian quarry tiles one inch thick and hard as hell. floor is very flat didnt seem any good reason to remove. thoughts?