After years of reading the IRC deferring to the IBC deferring to PTI and looping around endlessly, interrupted only here and there by exceptions allowing the building official to decide this and that, I still cannot make an air-tight argument that a slab-on-grade in expansive soil must be:

(1) designed by an engineer or "design professional"

(2) inspected by that engineer during the process

While I'm at it, how about soil testing to proceed the construction of the above foundation? PTI says that soil testing "shall" occur. IRC and IBC say that you must adhere to PTI requirements, but then say the building official can decide.

Jeez! Any ideas here?

Thanks,

Aaron