Porcelain floor tiles loose on floor

Sorry to here that you're got problems. Could be many reasons for this happening. If it was sand and cement screed, was it dry? Was the floor primed correctly? Was it a anhydrite screed ? If so was it dry? Was correct primer used? Was correct adhesive used? With both substrates was the UFH commissioned before tiles were lay? What is the max temp your plumber has set the floor to reach, should no be able to go above 28 degrees. Is there any expansion joints? I would always use an uncoupling membrane, your tiler has not. If you have had some come up then you may find this will keep happening. If it is in one area that this is happening it may be that that area of floor has been contaminated. Most common I have found is the plasterers have knocked up and got plaster all on the floor. This has to be removed prior to priming and tiling. Best way to clean the tiles is with a 4" grinder and a good blade, you should not attempt this yourself, let the tiler do it as could be unsafe. The adhesive will not sock of, if you find it does then you have found the root of your problems. Hope this helps Julian

If you mean Super flow which could be a type of anhydrite screed,did the tiler know that a residue known as laitence forms and this must be removed and primed before tiling using a uncoupling mat.