buying qn apartment

To say fact I completely discourage you not to buy it, because, neither ceiling nor flooring will be yours. when it is not going to be yours . why should we take a trouble in it.

Seek advise of a local architect or civil engineer

It is not a legal dispute for consideration of experts on this platform.

Generally building's average life is considered to be 50 yrs and it may last much more depending upon quality of construction. Besides your own opinion after inspecting the apartment you may take help of the structural engineer in the matter to clear doubt. Please ensure proper OC is available for the apartment and the land is conveyed in the name of co-op society. If not don't burn your fingers and look for alternate opinions.