We note that your question relates to AS 1684.2-2010, but there is now a 2021 edition of AS 1684. However, the requirements for angle bracing in AS 1684.2-2021 remain the same.

You will find aerosols and brush-on products on the net described as H3 treatments, but they are 'supplementary products' intended for treating cut ends and notches in timber that has been through a preservative treatment plant. They are not marketed as an alternative to H3 pressure treatment. H3 treatment penetrates into the timber and provides protection against termites and wood rot. H2 treatment protects timber only against termite attack.

Metal or timber fascias can be used in BAL-FZ areas, over fire-resistant linings. This is shown in our Regulatory Information Report RIR 23626A which can be downloaded from our website free of charge via this link https://www.woodsolutions.com.au/resources/standards-codes/fire-test-reports. Refer section 9 of the report for details of the fire resistant fascia linings, and section 10 for installation of the fascia itself.

The metal sheet roof system for BAL-FZ (Flame Zone), assessed by Warringtonfire, was based on 15mm pine plywood or 15mm OSB roof lining. 

Our Technical Design Guide #08 includes span tables for stringers and stair treads. A copy can be downloaded free of charge from our website via this link https://www.woodsolutions.com.au/publications. Alternatively, a hard copy can be purchased here https://www.intertekinform.com/en-au/search/standard/?searchTerm=WS08&productFamily=STANDARD&q=WS08.

We assume the outriggers will be supported on the external wall. Note that they will need to be adequately tied down to the wall, and to the supporting rafter, given they will be within 1200 mm of the edge of the roof.

Warringtonfire’s Regulatory Information Report 45980.10 confirms that hoop pine and radiata pine 9mm thick or greater fall into Group 3. A copy can be downloaded from our website via this link https://www.woodsolutions.com.au/resources/standards-codes/fire-test-reports. Although originally to expire on 31 December 2023, RIR 45980.10 has been extended to 31 December 2025.

Sprinklers are not essential but without sprinklers, according to NCC 2022 clause S5C20 (2), the carpark in the lowest storey and the floor between it and the Class 2 part above would have to be of concrete or masonry. So the lowest storey is virtually a concrete/masonry box with the timber-framed Class 2 occupancies on top.