sizing standees in a concrete slab

[Steve1955]

I have a 2' thick conc slab w/ #7 rebar top & bot mats. Should I us a #3 standee or go up a size to a #4 standee?
When should you change size of a standee from a #3 to a #4
seperating mat in a ftg?

 

[4wilmar]

CRSI Manual of Std. Practice does not actually recommend #3 standees. For slabs 2 ft thick & less you should use #4 standees (see section 3.14.2) spaced at about 3-4 ft.