What is the collective noun for flats?

There isn't a widely accepted collective noun specifically for flats. However, depending on the context, you could use some of these options:

* A block of flats

* A complex of flats

* A development of flats

* A row of flats

* An apartment building

You could also use a more general term like a collection of flats or a group of flats.

Ultimately, the best collective noun will depend on the specific context and what you want to emphasize.