There is no empty hour, only quieter ones
Continuously occupied premises still have rhythms. Lobby traffic falls between certain hours, arrivals cluster around particular times, and the restaurant, meeting space and gym each have their own quiet periods. Mapping those is the foundation of the schedule. The aim is not to find an empty building, which does not exist, but to place each task in the window where it causes the least intrusion and can be done properly.
Write the windows into the scope with the tasks assigned to each, rather than describing an overall shift. That level of detail lets a bidder plan the labour properly and lets you check whether their proposal actually fits the building. A quote that assumes one continuous overnight block in a premises with steady overnight arrivals has not understood the requirement. It is also the detail that tells you whether a bidder has visited the premises at the hours it matters.
