To dream of a derelict building represents a neglected area of your life that is beyond fixing or returning to. Having left something alone for so long that restarting it or repairing are out of the question. Alternatively, a derelict building represents memories of failed friendships, old relationships, or feeling uncomfortable remembering a disappointing failure.
To dream that a building or space is derelict may also represent your feelings about how terrible it is to notice an area of your life never being paid attention to again. Feeling that some area of your life didn't get the chance it deserved or blew it's only opportunity to succeed.