Deteriorated or “spalled” joints are the number one problem in a concrete floor. Saw cut contraction/control joints and ...

As joint spacings and concrete shrinkage increases ... With Option 2, we allow slabs to crack randomly but control crack widths with steel reinforcing bars or welded wire reinforcement.

Wet concrete ... or other slab without thickened edges, use 2x6s. If you can’t get long enough boards, splice them together by nailing a four-foot 2×12 cleat over the joint.