Rebar Overlap Rule

Lapping of rebars has long been treated as an useful, inexpensive splicing system. While placing steel in Reinforced concrete structure, when the necessary length of single bar fall short, lapping of two bars side by side should be provided to retain the desired design length.

Rebar Lapping is inevitable if a run of the rebar is larger than one solid piece. Under this situation, it is required to overlap the bar in that line. It should be noted that the overlap should not be provided in bars with diameter in excess of 36 mm.

In such a situation, welding should be applied. But if welding is not possible in some situations, then lapping should be provided for the bars greater than 36 mm diameter. But together with lapping, supplementary spirals of 6 mm should be arranged around the lapped bars.

Reinforcing bars (rebars) are available in lengths of up to 60 feet. But practically, most building projects entail large-scale rebar splicing because of shipping constraints on length and proper application of materials. A lap splice is considered as the most recognized system for providing a single structural entity from two rebar segments.

Lapping is formed by overlapping two lengths of rebar, then wiring them jointly.

The overlap requirements differ with both rebar size as well as the particular structural application. Lap length for concrete of 1:2:4 Nominal mix:

The Lapping length in tension (MS bar – mild steel bar) along with anchorage value is 58d. Therefore, after deducting the anchorage value, the lap length should be = 58d – 2*9d = 40d. (Here 9d = hook allowance up to 25 mm and k=2)

Lap length for M20 concrete:

Also Read: Importance of perfect lapping of steel bars in RCC construction works

• Columns – 45d
• Beams – 60d
• Slabs – 60d

It signifies that if it is required to lap 20 mm diameter column bars, a least lap of 45 * 20 = 900 mm is provided.

In this regard an exclusive video tutorial is presented by the renowned engineer S.L. Khan. Go through this exclusive video tutorial to learn how to workout the rebar overlap/cut length of overlap.

To get more details, go through the following video tutorial.

Video Source: SL Khan