We are not aware of any limitation on the use of mass timber for health projects. In fact a number of health-related buildings have been completed in various countries including Australia, for example here https://www.buildaustralia.com.au/projects/new-landmark-timber-health-and-medical-precinct-opens-in-norwest/. In saying this we are talking about the structure.

In BAL-40 areas 9 mm fibre-cement is a deemed to comply wall cladding on its own, as long as it is backed by sarking on the outside of the house frame - refer Australian Standard 3959:2018, clause 8.4.1 (b) (i). So an additional layer of fire resistant plasterboard is not needed. 

We understand native forest logging will cease in Western Australia from the end of 2023, so not only jarrah but also karri, marri and other native species will no longer be commercially available. In our view this is unfortunate given that all jarrah harvested in recent years was from regrowth forest areas, ie.

Australian Standard 1684, Residential timber-framed construction, deals with the design of the roof itself (member sizes, tie-down to resist wind uplift, etc.) but not the connection of a new roof to existing brickwork. This would usually be done by fixing a ledger board to the brickwork, which in your case appears to be a solid wall, the thickness of two standard bricks. We are not aware of an Australian Standard that covers this, but there is some advice on the net.

The way to deal with potential splitting between bolts is to make one of the bolt holes a 'slotted' hole, ie. oversized.

There are two types of moisture meters, electrical resistance meters and capacitance meters. The type of meter that's best for you will depend on what you want to use it for. Resistance meters are more accurate but are slower to use since they involve driving pins into each sample to obtain a reading. A hammer electrode would be needed to test hardwoods and will be equipped with two insulated pins. Each test leaves two pinholes in the wood. Since the electrical resistance of different species varies, corrections need to be applied to the meter readings.