Placement matters more than quantity
Rebar only works in the tension zone. In a slab on grade that means the lower-middle third, held up on chairs — not laid on the gravel and 'pulled up' during the pour, which almost never actually lifts it.
- • Keep 3 in of cover from soil, 1.5 in from formed edges.
- • Use chairs or dobies every 3–4 ft along each bar.
- • Fiber mesh controls shrinkage cracking; it does not replace structural rebar.
FAQ
How much rebar do I need for a concrete slab?
A typical residential slab uses #4 rebar on an 18 in grid. For a 24×24 slab that's about 700 linear feet including laps.
What spacing should rebar be?
12 inches for heavy loads and driveways, 16–18 inches for standard residential slabs, and 24 inches for light-duty pads.
Do I need rebar in a 4 inch slab?
For sidewalks and small pads, fiber mesh is often enough. Anything carrying vehicles or supporting a structure should have rebar.
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