went to look at a floor today.....43m2 sand cement screed, no under floor heating, but running round the edge if the room, and running through the middle of the floor are some heating ducts approx. 200mm wide, made from 3 quarter inch wood, its well constructed with no movement .....tiles are going to be 450mm porcelain, going to be using flexible adhesive and grout.....anyone come across this before, did you do any extra prep to the floor.?