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Carzonia Apartments - Improvised housing made from old streetcars after the 1906 earthquake
(ani.social)
From an article on these: https://www.outsidelands.org/carzonia.php
Think about what things would have been like after the earthquake: Any building materials and labor would have been in extremely high demand.
The faster that one could put up anything to house people, the better, even using "waste materials" like old streetcars.
At least these had a solid roof and walls.
No doubt there was even more temporary housing that would resemble homeless huts that we see today.
Sadly, according to the article, these didn't stay for very long, and were replaced by more traditional construction after 4 years.
I mean, I'm more surprised they bothered with the foundation at all really. It's not like they couldn't have slapped it on the ground with some wheel chocks and called it a day. In fact, I know of people in the 21st century doing that with old W-class trams here in Victoria.