Electric underfloor heating is suitable for use beneath mosaic tiles however a levelling compound must be used above the heating before laying the tiles to ensure the tiles lay flat.
Tiles are very efficient transmitters of the heat from underfloor heating and they radiate it effectively into the room, however the thicker the tile is the longer it will take for the heat to make its way through. You should always ensure you use a flexible tile adhesive and grout suitable for underfloor heating and the tile adhesive should be used to make a complete bed otherwise unheated patches will be felt above the air pockets.
Beneath tiles you have a choice of electrical underfloor heating systems. The most efficient systems are based around high output undertile heating mats or cables with outputs around 200W/sqm as these systems warm up very quickly. A suitable alternative, particularly in well insulated rooms, is a 160W/sqm heating mat system and like the 200W/sqm mats this system can be used on top of thermal insulation board to shorten their warm up time and increase their efficiency.
In addition to undertile heating mats you can use an in-screed heating cable beneath tiles however as the cables are normally at least 50mm beneath the tile surface these systems take far longer than heating mats to warm the tiles. In-screed systems do provide a more stable temperature however, and they are particularly suitable for rooms that are constantly heated or where the night storage rate is used as they can ‘charge up’ the screed bed over night.