Building approvals data is not just the number of residential dwellings. Total value of all building approval work for Cairns SA4 and Cairns City SA2:
I can think of a couple of data series to correlate with this but may need to lag the 12 month moving average here a bit. The most recent big spike was I think (?) Nova City approval where we are still awaiting long anticipated developments. Crane count in the city maybe something to watch as the GA bump works through and with CPAC also now completed.
Noted also that the most recent monthly spike in March 2019 is not correlated with approvals in Cairns City. This appears to be significant non-residential approvals in Gordonvale and Innisfail.