Rebar spacing and sub-base depth typicals
Typical industry planning values — NOT a structural/geotechnical design. A licensed engineer sizes load-bearing concrete, footings and reinforcement; confirm against your product’s spec sheet and local code.
Residential flatwork typically uses #3–#4 rebar (or welded wire mesh) at 12–18" on center over a compacted gravel sub-base. The values below are labeled planning typicals — NOT a structural or geotechnical design; a licensed engineer sizes load-bearing concrete, footings and reinforcement. Use them with the rebar calculator and the gravel / sub-base calculator.
| Item | Typical planning value |
|---|---|
| Rebar size (residential flatwork) | #3–#4 bar (or welded wire mesh) |
| Rebar spacing | 12"–18" on center |
| Lap / overlap | 10% (add to linear ft) |
| Gravel sub-base depth | 4"–6" |
| Gravel density | ≈ 1.4 tons / yd³ |
Labeled planning typicals — NOT a structural or geotechnical design. A licensed engineer sizes load-bearing concrete, footings and reinforcement; confirm against local code.