Welded wire mesh
Also called: wire mesh, WWM, welded wire fabric, WWF, remesh
Steel reinforcing fabric — usually 6×6 inch squares of 10-gauge wire — laid in the middle of a concrete slab to hold cracks tight and keep the pieces level. Standard for patios and pads; garages and driveways use rebar instead.
Mesh is sold in 5×10 ft sheets (about $10–$15) and 5×150 ft rolls. The common residential grade is 6×6-W1.4×W1.4 — 6-inch squares of 10-gauge wire. It’s laid with sheets overlapped one full square, stopping 2 inches short of the forms, and set on chairs or dobies so it sits at mid-depth of the slab. Mesh lying on the gravel does nothing; “hooking it up” with a rake during the pour rarely gets it where it needs to be.
Steel in a slab doesn’t prevent cracking — control joints manage that. It keeps the two sides of a crack from separating or stepping, so the slab stays flat and the crack stays hairline. For a patio, walkway, shed pad or hot-tub pad on well-compacted ground, mesh is enough.
Rebar — #3 (3/8 in) or #4 (1/2 in) bars tied in a grid on 12–18 inch centers — is stiffer, easier to keep at the right height, and the right choice for a garage floor, driveway, workshop, or any slab on clay, fill or expansive soil. It adds $0.50–$1.50 per square foot. Fiber-reinforced concrete reduces surface crazing and is a cheap add-on, but it isn’t a replacement for either.