Structural 22mm HardieFloor for wetroom?

[D-Eye-Wire]

Hi all,

(I have tried looking but could not find this subject covered in another thread, if I am mistaken please point me to the correct thread and I will try to cancel this posting)

Replacing a small 3sqm washroom with a wetroom, and contemplating the use of Hardie's 22mm structural board hardiefloor (Structural Fibre Cement Interior Flooring - hardiefloor in a bid to achieve levelling with existing floorboards in the neighbouring room and the 22mm Impey wetdec former. Would most appreciate some advice with the following:

Does anyone have any experiences to share or recommendation on regarding the product and proposed application?.

The plan is to:

1. Strengthen joist work (trimmers/noggins screwed with 10*4 or 12*4 spax quality screws).
2. Lay insulation between joists any recommendation on which insulation.
3. Replace an existing aav heading into the attic with an A1 AAV raised to 200mm above the highest wet entry's centre line - this aav will fit within the joist space.
4. Fix hardiefloor - (spax quality 50mm screws at 100-200mm intervals, 25mm from t&g edges, 12mm from butt edges + gripfill type adhesive on joists and silicone sealant on t&g ends and screw heads).
5. Apply tanking membrane (preparing hardiefloor according to chosen tanking system e.g. Priming)- was planning on using impey's tilesafe but given its vertical tile load and heating limits i am looking for alternatives - perhaps impey's waterguard, i will be going through other threads on this forum to understand different tanking membranes.
6. Securely fix rcd protected uht (compatible with the chosen tanking membrane) any recommendations for uht systems?
7. Consider applying (depending on the robustness of the uht mats) slc for general floor area and slurry of rapid setting flexible tile adhesive on former tray.

Lay tiles with flexible adhesive and grout that are compatible with the chosen membrane system.
Any other advice or highlighting of missed steps would be appreciated.

Given the small area I intend to waterproof full length of all walls. But as yet have not decided on which route to take. E.g. Hardie or aquapanel with membrane or wedi/marmox setup.

Thanks in advance