In may 2009 i did a bthroom conversion for a very good customer using travertine honed and filled tiles(customer choice),bal natural stone adhesive and bal superflex grout-all supplied by topps tiles.The basic plan was rip out old suite and shower and walls,make good and check floor(concrete),install floor drain and tank.re tiling commenced with a electric heating mat over 6mm insulated sheet and primer/pva on the subfloor,the wet area being in one corner of the room.on compleation all looked fine but i did report cutting problems to customer and topps at the time-tiles crumbled or cut rough.i allowed 6 weeks before turning on the heating system and all was ok-after about a month i had several tiles lift in one area-followed by 5 other areas over the last 14 months.lift the tiles and find the adhesive gone to powder behind,relay using new adhesive problem solved....latest batch off tiles lifted 2 month ago-heating system switched off since april this year-same probs with the adhesive,Bal rep inspects and report says no problem with adhesive.Also a fair few tiles are chipping at the edges and breaking away-2 coats of sealent was applied on compleation-also no probs with tiles in wet area lifting but 3 have large chips on edges-its sending me up the wall and customer is rightly getting fed up!.anyone had similar probs or got any ideas?-i still think adhesive was faulty and reacted to heat and perhaps bad batch of tiles-either way at the moment it blame the tradesman time...