pre-engineered foundation details
 

pre-engineered foundation details
are pre-engineered columns bolted directly to the slab or is the baseplate actually 2" above the slab with nonshrink grout installed (so that a column leveling nut can be added, similar to conventional steel)
any good reference material showing typical details of the foundation connections.
generally they are bolted directly to the slab, since the elevation of a properly constructed slab is held to a tolerance which does not require the grout bed.
the office that i work in specifies the columns are below the slab with 2" minimum between the bottom of the plate and the top of the foundation. you can specify the building any way that you prefer.