A structure is in ruins when it is left standing indefinitely while partly demolished or with significant structural damage.

When a building is returned to recognizably usable form after a partial demolition, then it reverts to being completed and is not classified as in ruins.

In special cases, a structure which is partly destroyed during construction and allowed to stand indefinitely in that form can be in ruins without ever having been completed.

Structures are never classified as in ruins solely on the basis of being vacant. Significant damage to the facade and/or framework must have occurred and been left unrepaired. A structure can be listed as in ruins on the basis of internal damage only if major structural elements like floorplates and columns are destroyed.