I talked to a guy the other day that moved 6,000 albums into a 100 year old house. He put them in the center of the bedroom floor above the living room without thinking. He said one night he was sitting in the living room, and noticed a large crack in the ceiling. Apparently, the weight from all those albums was causing the whole floor to sag. So he went up, and gently moved the albums from the edges of the stacks systematically going around the stacks, and putting them along the walls, being careful not to put any extra weight on the center of the floor.