Suspended floor 2

[Essex]

Back with problem of the floor construction for the Victorian offshot to 14C Essex hall house.
We have consent for a downstairs shower room and I would like a wetroom construction. It will be for my 90year old mother.
So, has anyone any experience of putting a wet room construction on limecrete. Seems like a contradiction in terms and certainly would not breathe, would send damp up walls.
So am coming back to a suspended floor.
Middi, what is a "slit cut and mortared" technique? Tried googling but got nowhere. Embarassing not knowing as I am an architect.
Currently I am thinking limecrete oversite (building regs for rodent protection, and we collect rats on a regular basis), galvanised joist hangers, (the Victorian brickwork is good) and treated timber joists.
Have spent a lot of time specifying materials that do not contain chemicals, what timber treatment is the greenest?
Will put a plastic tray in for wet room, and t@g flooring in remainder.
All comments/help gratefully received.

 

[DJH]

I recall fitting lead trays under both baths and showers in the past especially when they were situated on the first floor over an ornate ceiling below! any spillage or overflow was catered for by an overflow pipe extended through the wall to outside, again in lead to match everything else that stuck out.