In a message dated 5/11/2014 12:02:53 P.M. Eastern Daylight Time, [log in to unmask] writes: Hmmm. Sort of. You have a specific vault in mind? Or, are you curious about the iconic herring-bone pattern of tiles? I have no vault in mind. I just wonder why I have never seen an example of that kind of failure on the typical Guastavino, thin-shell tile peeling away from the underside of the vault. It's not like the tiles are wedged in place, like voussoirs, I don't think. They are just glued in place, and they've been fighting gravity for a century. Christopher -- **Please remember to trim posts, as requested in the Terms of Service** To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: <http://listserv.icors.org/archives/bullamanka-pinheads.html>