S
SJPurdy
with a sand cement screed and I assume (until told otherwise) an anhydrite screed, as the screed sets/cures it shrinks a bit and this sets up stresses in the screed as it tries to pull itself into a less stressed position (it can slide a bit over the insulation layers etc underneath it. When the floor is heated up for the first time(the commissioning) then it will possibly 'slide' a bit more to find its less stressed position when heated; and often if it is a (non rectangular)shaped floor cracks in the screed may occur as points of high stress are released. Now if the floor is already tiled when this first distressing occurs then the tile layer will have to cope (if it can) with the movement.
