[erikprotagonist]

During the 1800s there were four sets of building regulations (or rather, laws) for Christiania (the name of Oslo back then), which regulated everything from the width of the streets to how many floors buildings could be. In 1827 the minimum street width became 11.35m, then 12.60 in 1842, 15.75 in 1875 and 20m in 1899. (https://no.wikipedia.org/wiki/Murbyen_(Oslo) has a good overview).

The background for the regulation was the switch from unregulated wood buildings to requiring mainly brick as building material - there were some major fires before using bricks became the law.

I live just around the corner from one of the photos - the building in that photo hasn't changed much since back then.