A rebar grid works better than steel mesh to prevent cracks. Held together with tie wire, a rebar grid set on 2-in.-tall concrete spacers stays put during the pour and the screeding. Wire mesh often ends up at the bottom of the slab, where it can’t provide structural support. Concrete Tools, Concrete Footings, Concrete Projects, Concrete Patio, Concrete Formwork, Pouring Concrete Slab, New Home Construction