[wvh]

This is what is called "tiivistettävä" in Finnish. I live in such an area, with traditional wooden housing, in the city core. If some houses get in bad state, the city orders to throw them down and some low-rise apartment blocks are built on top of them, thus increasing the number of people that can be housed per square meter.

It's a fine line between the noble intentions of the urban planning concept and creating a horrible mismatched pot-pourri of different building styles and ages, though. Ideally buildings in an area are somewhat congruent with each other.

Urban sprawl is an issue here in part because of the abundance of water, land-locking expanding city centres.