Libraries and archives require specially reinforced floors, capable of bearing (I think!) 300 lbs/sq.ft. This makes them more expensive to build than many other things.

The old story about _______________ University's library slowly sinking because the weight of the books wasn't put into the calculations is just an old story. No university library has done that. I am, however, trying to get the staff to believe that of my public library -- so far unsuccessfully.

The greatest weight of books here will be in the basement. If THAT floor crashes I've got bigger problems that I care to think about.