Clause 26.2.5 specifies requirements for lapping (splicing) reinforcement bars. Lap length depends on the development length, the percentage of bars lapped at a section, and the type of member. Lap splices must transfer the full design force from one bar to the next through bond with surrounding concrete.
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Key Requirements
•Lap length for tension bars: factor × Ld, but not less than 30φ or 200 mm
•Factor = 1.0 when ≤ 50% bars lapped at section; 1.3 when 51–75% lapped; 1.5 when 76–100% lapped (flexural tension)
•For direct tension: lap = 2 × Ld, minimum 30φ
•Lap length for compression bars: Ld in compression, minimum 24φ
•Laps should be staggered — not more than 50% of bars should be lapped at one section
•Lap splices should be avoided in regions of high stress (plastic hinge zones, mid-span of beams) and at bends
Reference Tables
Lap Length Multiplication Factors (Clause 26.2.5.1)
% Bars Lapped at Section
Factor (Tension)
Factor (Compression)
≤ 50%
1
1
51%–75%
1.3
1
76%–100%
1.5
1
Direct tension (any %)
2
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Formulas
Lap = k × Ld ≥ max(30φ, 200 mm)
Lap length for tension reinforcement
Lap = Required lap length in mmk = Factor from table: 1.0, 1.3, or 1.5 depending on % bars lappedLd = Development length from Clause 26.2.1φ = Nominal bar diameter in mm
Practical Notes
✓On most Indian sites, 100% bars are lapped at one section (factor 1.5 applies). Engineers should design for this reality even if they specify staggered laps.
✓For Fe500 in M25 with 100% lapped: Lap ≈ 1.5 × 47φ = 71φ. For 16 mm bar: 71 × 16 = 1,136 mm ≈ 1,150 mm.
✓IS 13920 (seismic) mandates: laps only in the middle third of member length, 100% splice factor, closed stirrups over the entire lap zone at spacing ≤ 150 mm.
Common Mistakes
⚠Lapping all bars at the same section (column-beam junction) — this creates a weak plane. Stagger by at least 1.3 × lap length.
⚠Using tension lap length for compression bars — compression laps are shorter (Ld in compression, min 24φ).
⚠Forgetting the 200 mm absolute minimum — even for small bars (6 mm, 8 mm), lap cannot be less than 200 mm.