Chimney Question??

Or a bucket truck...

If you go with a 24" X 24" chimney (still using 8/8 tile, just two rows of solid-core 4" block around the tile) instead of 16"x16" you can insert rebar "steps" into the block/mortar joints and have a fairly sound and safe means of accessing the top of the stack. this is common in europe where tile roofing prohibits walking on roofs to access the stack. It's also fairly common in industrial small commercial stacks. I've never seen it done on less than a 24" chimney and would have to surmise that the 16" stack commonly used is too small and light to safely allow a person to climb it.