O
On one
Hardie say that only a non flexible adh is required and that is only required where the floorboards require gap filling,so even the adh may not be required in this case if the floorboards are new(and flat)Hey @Lakey,
I've changed the thread title so that your question is more relevant.
It was a little confusing.
Using Hardie will suit your purpose just fine.
And using a flexible adhesive for both the Hardie and tiles would be the right way to go imo.