Throughout the country, many building permit offices require welded wire reinforcement to be placed in concrete slabs on grade. The wire is supposed to be placed horizontally at mid-depth of the slab. Unfortunately, in the field this requirement often translates to the wire being placed on the bottom of the slab where it provides no reinforcement benefit. To help avoid this possible code violation, insist that your concrete subcontractor uses "chairs"—devices made specifically to hold the wire mid-slab during the pour. An alternative to using wire in the slab is concrete mixed with carbon fibers that will help the slab resist cracking. Be certain to check with your building inspection department to see if they allow fiber cement mix as an alternative to wire reinforcement.