As a forensic engineer, I've been looking at this sort of stuff, pretty much every day, for 25+ years. I learned long ago to never, ever say "I've seen it all' :rolleyes: Case in point was an assignment just this morning for a chimney collapse. I'm guessing the builder was a decent Jenga player.

http://forums.pelicanparts.com/uploa...1271439163.jpg

http://forums.pelicanparts.com/uploa...1271439179.jpg

http://forums.pelicanparts.com/uploa...1271439560.jpg

Now the neighbors know why no smoke ever came out of the outer stacks.