Hi, i'm fitting electric underfloor heating in bathroom, i've removed all the old floorboards and laid 18mm wpb, then 18mm ply, followed by 2 coats of thermacoat acrylic primer. Instructions on the underfloor heating(screwfix one) say to bed the mat in screed, allow to dry then lay the tiles. As i've already raised the floor by 18mm + the depth of the tiles, i would prefer to just bury the heating mat in the tile adhesive(10mm) is this ok, i'm not too fussed about losing a bit of heat, or is there a specific reason for laying the mat 1st?
