Looking at the building I would say its a 1940's with a fake art deco'like facade. The external plumbing puts it as pre mid 50's by which time they were using internal risers.
Try these guys, they did work on some spalling repairs at my former PPOR block and were pretty good.
http://www.remedial.com.au/structural-repairs/building-solutions
Unless there is a dire shortage of land available, it going to be cheaper for a developer to buy 2-3 old houses and bulldoze them to build rather than buy out 18 units each with a price premium, demolish and rebuild.