An important thing to consider is the required clearance of 250mm under the deck to allow sufficient airflow to avoid rotting of timber frame. This may play into your decision given how much extra you may need to clear.
Concrete slab + screed is the most efficient way to do it. I just don't know the difference in cost.
Hi @ProjectPete thank you for your help.
Looks like concrete it is for this section.
You mentioned 250mm clearance regarding my previous post which is another section of tiling on steel frame and secure boards, unlikely we'll have a 250mm clearance is that an issue?
250mm clearance is required for timber (frame/deck).