We have CRF and Smoke Development values for a number of timber species, but unfortunately not for Baltic pine. Nor do we know of a source of this data. Perhaps the importer could provide details, or arrange for the required tests.

Your best source of information is a Technical Data Sheet titled Timber Decks - Commercial, Industrial & Marine. It's number 7 in a series published by Timber Queensland, and can be downloaded via this link http://www.dtmtimber.com.au/downloads/TQ_TDS/tds_07_Timber-Deck_final.pdf. Table 4 gives decking board spans under different load conditions. Spans vary according to the stress grade of the timber.

The main aim of AS 3959, Construction of buildings in bushfire-prone areas, is to prevent fire from entering the building from an external source. We consider it is the fire resistance of the wall in total, rather than the outer skin, that must resist fire in BAL-FZ areas. In the case you describe it seems the required fire resistance level (FRL) of -/30/30 would be provided by the core-filled blockwork, with hardwood cladding as a decorative overlay.