Rebar or Wire Mesh: Which Does My Slab Need?
Here's the first thing to understand: reinforcement doesn't stop concrete from cracking. Concrete shrinks as it cures and moves with temperature, and it will crack. What steel does is hold the pieces tightly together so cracks stay hairline instead of spreading, and carry tension loads the concrete itself can't. The choice between rebar and mesh comes down to how much load the slab has to handle.
Welded-wire mesh — for light-duty slabs
Welded-wire mesh is a flat grid of light wires (commonly a 6 × 6 inch pattern) that sits in the middle of the slab and controls shrinkage cracking. It's the right, economical choice for patios, walkways, shed floors and other slabs that won't carry vehicles or structural loads. It's cheaper and faster to place than rebar. Two rules make it work: overlap adjacent sheets by one full square, and keep the mesh in the middle of the slab thickness on chairs — mesh lying on the subgrade does nothing.
Rebar — for structural and vehicle loads
Rebar is deformed steel bar laid in a grid, and it's what you want anywhere real load is involved: driveways, garage floors, footings, and slabs supporting walls or heavy equipment. For residential slabs-on-grade, #4 (½-inch) bar at 12–18 inches on center is typical, tied into a grid and held up on chairs. The exact size and spacing should follow your design or local building code — structural reinforcement isn't a guess.
| Slab type | Reinforcement |
|---|---|
| Patio, walkway, shed floor | Wire mesh (or fiber) |
| Driveway, garage floor | Rebar grid |
| Footings, structural slabs | Rebar, per code |
Can you skip reinforcement?
Very small, lightly loaded pours over a well-compacted base sometimes go without, and fiber-reinforced mix is an option for crack control in light slabs. But mesh is cheap insurance, and on anything that matters the cost of steel is trivial next to the cost of replacing a cracked slab. Whatever you choose, keep the steel positioned correctly and pair it with control joints, which decide where cracks form.
Estimate quantities with the rebar calculator (bar count, linear feet and weight from your grid) or the wire mesh calculator (sheet count with overlap). For the slab itself, start at the slab calculator.