The existence phase extends from the end of construction until the beginning of demolition, including periods of reconstruction or renovation. It also applies to partly destroyed structures which are allowed to remain standing in the present form.

This status begins when a structure is first ready for use, provided that its framework and external structure are basically finished. Interior fit-out often occurs well into this phase, and is not sufficient to keep a structure listed as under construction; it is only necessary that the capacity for usage exists, i.e. the structure can be handed over to its tenants. A vacant structure, or a structure which is no longer serving any useful purpose, does not change its status until actual dismantlement or demolition begins.

Physical readiness for use begins the ordinary existence phase. Actual occupation is not required, and subsequent vacancy does not by itself end the structure's existence or place it in ruins.