there is still a long way to go with this floor every part has been pushed to its limits and beond looking for the answers can you lay tiles only 4mm above the pipes its breaking all the rules the heating has not been turned on and there are no exspasion joints to door ways wont be for a couple more weeks using thin tiles .and whats being tested on the bathroom floors with wet under floor heating will push it all the way .keeping the hights to the minnum only time will tell