(Image: AAP/Darren England)

Pretty much everything about the current economic contraction is unprecedented -- but one very familiar phenomenon could be emerging that will extend and deepen the crisis.

The health of the commercial property sector is always a key indicator for financial and corporate regulators. When big problems emerge there, they have a real risk of endangering the rest of the property sector, the financial system, and the wider economy.

Commercial property isn't just office towers and shopping centres -- since 2015, apartments and home units have taken a larger share as construction has boomed across Sydney, Melbourne, Brisbane and their hinterlands. There have also been plenty of hotels built, often as part of apartment projects.