Just a couple of links to get you started.
Why were these magnificent buildings demolished 1926/1927?
When were they built that they were in need of demolishing?
What was the real reason they were demolished?
This was just Sydney.
Album – Demolition Books – Volume 14
This is an entire book cover to cover. Select each page from the thumbnails across the bottom of the page.
https://archives.cityofsydney.nsw.gov.au/nodes/view/1952324
https://archives.cityofsydney.nsw.gov.au/nodes/view/1952414