rule of thumb when to use monolithic turn-down slab vs slab same thickness

[delagina]

If I have an equipment on skid say 40' long and 15' wide, should I just use 1'-2" thick slab (it's 1'-2" because the grade varies).
Or 6" inside slab thickened at the edge (monolithic turn-down slab).
What is the rule of thumb on this. This is concrete savings vs difficulty of forming.
Weight of equipment is minimal.

 

[jayrod12]

You could detail it as a thickened edge slab but note to the contractor that a constant thickness option is acceptable. Then the ball is in their court to construct the most economical detail.