Earlier quoted context omitted.
For a lot of the office buildings I've been in, there aren't that many toilets per floor. Its also different when you've got some toilets that are often unused compared to people running laundry, cooking, bathing, etc. Very different demands on the plumbing system. You also then had everything pretty much isolated to two rooms for an entire floor meanwhile now every unit is going to have a separate kitchen, a bathroo…
But do you really have to cram in as many residents as you could with a purpose-built tenement? There must be ways to keep headcount in the range the infrastructure can support and still provide a lot more housing than just leaving them as empty decaying offices owned by the last one holding the bag. Intersperse flats with windowless storage units (you have a depth problem anyways), low density commercial use like wo…
Demolishing the office building and building a residential building is more profitable often.