Two questions decide what a building is for. The first one locks.
A building is the block itself, above the flats. You create one when you manage or own a whole block, not single flats on their own.
On Properties, select Add building. Name it, then choose your role — the choice that shapes everything after.

There are two roles: you own it and let the flats yourself, or you run it for its leaseholders. A leaseholder building unlocks service charges and ground rent; an owned one treats the flats as your own.
If you run it for leaseholders, we also ask whether you hold the freehold.
A short set of questions follows — a lift, a water tank, common parts, when it was built. Each is Yes, No or Not sure, and as you answer, the duties the building must hold appear alongside.
Not sure is a fine answer, and you can change it later.
Select Create building to finish.