Well, if each building in Off Topic represents a thread, the number of floors the building has should be equal to the number of pages the thread has.
So this thread would be about 30 floors tall ( however this is implying the thread stays at this number ), a thread with 3 pages would have 3 floors, and some really long threads such as "Post real life pictures of yourself" and another certain thread would be so tall, they would go off the screen.