Slab on Grade - Control Joint Location

[m1ke99]

If I have a 20ft x 20ft room with a sump in the middle, is it best to run the control joints diagonally from the corners of the room to the corners of the sump pit?
Or saw cut down the centre with orthogonal pattern?

 

[Ron]

For 20 by 20 slab, sawcut the joints within 8 hours of concrete placement and sawcut two joints, to break the slab into 4 equal square sections. Do not saw diagonally. That will cause cracking near the apex of each triangular section.

Sawcuts should be to a depth of 25 percent of the slab thickness.