This is just so not good. Worse because there is not obvious reason for it. No detectable building movement. Although the exterior air con unit sits there, it has done so for eight years and never been a problem. The air from the side of it is not that hot anyway. The only thing that has changed is that the windows have been tinted. As I said to R, the crack will get worse, and it has. Our insurers say, not their problem, so I guess Owner's Corporation insurance will pay. Fingers crossed.