Free To Canoe
Thinks s/he gets paid by the post
Other comments: It's very cheap to lay a set of 4" dia perforated pipes in the chips and dust before you pour the concrete for the slab. This can be used later to very inexpensively remediate any radon problems (via sub-slab depressurization) that show themselves after you've got the building finished.
So that is what the 4" steel riser pipe outside of my garage does!
Always educational here on the forum.
Free to canoe