Why three cleaners produce an unclean room
Each tenant's contractor has a scope tied to a leased boundary, and each one is behaving correctly by staying inside it. The shared floor is outside every boundary, so three competent contractors attend the building weekly and the common area deteriorates steadily. Nobody is at fault and the situation is entirely predictable once the arrangement is described, which is why it is worth describing rather than assuming somebody will pick it up.
The fix is structural rather than a matter of goodwill. Someone has to commission the common area as its own scope, with a stated area, a frequency and a party paying for it. That is normally the owner or the managing agent, recovering the cost through outgoings in the usual way. Once it exists, the boundary questions become simple, because there is a document that says where each responsibility starts.
