Looks like my Co. in Ky is going for a deeper bottom req. for footings. It was 12″ from grade to bottom of pour, 2, #5 rebars on chairs of 4” from the dig floor. Now it is 18”.
If I am planning a thickened edge slab ( derrrr I am) @ 5” and the aggregate packed is 4″ under it with 2″ of foam insul..just where do I calc the perimiter thickness..from grade or Top Of Slab.?
The Co. can’t answer w/o my pour in place (?????) for a certain refusal…Duane ( same as me) is clueless..same as me.
I THINK I can get undisturbed soil ( lotsa roots) for the perimeter at about a 6” dig and that would work for my FF to FF height, but won’t muster for the frost line req’s.
I have been here going on three yrs, winters are not like they were in the NE..is this a reasonable depth?
Case in point: Crawdads in April down the slope, solid Limestone just beneath the roots of a very LARGE Soft Maple tree..
Killing the tree is NOT an option yet, and root pruning is less desirable.
In Ky, the jelly state.
Spheramid Enterprises Architectural Woodworks
” Iam not a poet, but your hat is singularily inadequate”
Replies
When I was doing my footings I asked for clarification on what "grade" was. Generally, it's the top of the dirt. So I got passed up the chain to the top guy who wanted to know why I wanted to know.
Part of annual heat storage is insulating the footing (and surrounding dirt) on the outside of the house. Gotta keep that dirt insulated. Shocked the guy that anybody would insulate there. Had no interest in why, but asked if I'd consider the bottom of my patio slab "grade". Worked for me to avoid either: a stepped footing or abnormal depth. Now, they probably know what frost-protected shallow foundations are.
http://www.cs.arizona.edu/people/jcropper/desguide.html describes how to frost-protect a shallow footing. It'd be a better idea for you. Warmer floors are better. Your maple might not appreciate it as much.
18" here too, but even in winter shadow I've yet to see 8" of frozen dirt.
PAHS Designer/Builder- Bury it!