Rebar cover and lap splice — keep bar off the dirt and lap 40× the bar diameter
Two placement details: keep bar up on chairs (3″ cover cast against earth, ¾″ formed — ACI §20.6); and where a run needs splicing, lap 40 × the bar diameter (min 12″), stagger the laps, and tie every one (ACI §25.5).
What this diagram shows
Two rebar placement details. Left, concrete cover: bars sit up on chairs inside the concrete, not on the dirt, with 3 inches of cover where concrete is cast directly against earth and 3/4 inch where it is formed and not exposed to weather, per ACI 318-19 section 20.6. Right, a lap splice: where a run is longer than one stick, two bars overlap by 40 times the bar diameter (minimum 12 inches), the laps are staggered rather than lined up, and every lap is tied. Bars are never just butted end to end, and bars larger than #11 are not lap spliced (ACI 318-19 section 25.5).
Rebar Calculator
Free rebar calculator: exact bar count, linear feet, weight, and stock sticks to buy for slabs, driveways, footings and round pads. ASTM A615 & ACI 318.
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