D
dagger
i agree if you can go for the ditra put it in!,UFH and ply...i would use one all the time....lateral stress can crack any tile...might be over kill to some but i would rather walk away from a job knowing it was going to last years..
but 10mm of fibreplan over 25mm ply strenthend by the heatmat mesh (as a binder) i think dietra is overkill, that said if i had it i would use it so,
revised
1. over board 25mm ply screwed at 30mm centres,
2. lay heatmat and level with fibreplan
3. install dietra with keraquick
4.level ditra with fibreplan/keraquick
5. tile away!
6. grout with ultracolour plus
job done 10yr guarentee from me and dave!