Expansion gaps in ply?

[2020Tiling]

So why do they recommend using SPF to fill the gaps in Cement Board? surely it would be a safer option to use Silicon even though it should be rigid.

 

[2020Tiling]

Will Ditra or similar stop stress fractures?

 

[On one]

It's time to re write the instruction manual on floor preparation now IMHO .All wood will 'breathe' so it needs to be covered before the introduction of a moisture layer of adhesive so either a uncoupling membrane or cement boards should be used.

On a similar note....I can recollect from memory(a few years ago now) that 1 adhesive manufacturer required that overboarded wooden floors had to be ventilated.....so theoretically every 400mm(joist spacing) you would have to have have a vent hole........practically unlikely......but a get out clause for any failures.

 

[On one]

Will Ditra or similar stop stress fractures?

Not if you have any vertical movement in the floor joists