Lap Length of 32mm Bar: IS 456 Table & Calculator

Results

Check the working before you order.

Lap length in tension

1,813mm

In bar diameters	56.6 × db
Lap length in compression	1,450 mm
Compression in bar diameters	45.3 × db
Development length (tension)	1,813 mm

Uses the simplified code equations. Your structural drawings and the engineer of record govern: they may specify longer laps, different splice classes, or seismic detailing.

Stagger laps where possible, and do not lap bars larger than #11 / 36 mm in tension (ACI) or 36 mm (IS): use couplers.

Price This optional: add your own prices

Result to priceMaterial price per unitLabour rate per unitCurrency

Your prices are remembered on this device only.

Send Order WhatsApp, SMS or email to your supplier

Include

Delivery date Time Site / address Contact Notes

WhatsApp SMS Email

Working

τbd (M20) = 1.20 N/mm² × 1.6 (deformed bars) = 1.92 N/mm²
Ld = φ × 0.87 fy ÷ (4 τbd) = 32.0 × 0.87 × 500 ÷ (4 × 1.92) = 1813 mm (56.6 φ)
Compression: τbd × 1.25 → Ld = 1450 mm (45.3 φ)
Tension lap = max(Ld, 30φ) = 1,813 mm
Compression lap = max(Ld compression, 24φ) = 1,450 mm

Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.

Formula

σs            = 0.87 × fy                      (435 MPa for Fe500)
τbd           = table value × 1.6 for deformed bars   (M20: 1.2 × 1.6 = 1.92 MPa)
Ld (tension)  = φ × σs ÷ (4 × τbd)
Lap, tension  = Ld, at least 30φ   (2 Ld in direct tension)
Lap, compr.   = Ld ÷ 1.25, at least 24φ

Worked Example

A 32 mm bar in M20 concrete with Fe500 steel:

σs = 0.87 × 500 = 435 MPa; τbd = 1.2 × 1.6 = 1.92 MPa
Ld = 32 × 435 ÷ (4 × 1.92) = 1,812 mm (56.6φ); 30φ = 960 mm, so Ld governs
Tension lap = 1,813 mm
Compression: 32 × 435 ÷ (4 × 2.40) = 1,450 mm (45.3φ); 24φ = 768 mm → lap = 1,450 mm

Lap Length of 32mm Bar by Concrete Grade

Deformed (TMT) bars, flexural tension.

Concrete	Fe415 tension	Fe415 compression	Fe500 tension	Fe500 compression
M15	1,805 mm	1,444 mm	2,175 mm	1,740 mm
M20	1,504 mm	1,204 mm	1,813 mm	1,450 mm
M25	1,289 mm	1,032 mm	1,554 mm	1,243 mm
M30	1,203 mm	963 mm	1,450 mm	1,160 mm
M35	1,062 mm	850 mm	1,279 mm	1,024 mm
M40	960 mm	768 mm	1,145 mm	916 mm

More Lap Lengths by Bar Size

Frequently Asked Questions

What is the lap length of a 32 mm bar in M20 concrete?

1,813 mm in tension and 1,450 mm in compression with Fe500 steel, or 1,504 mm and 1,204 mm with Fe415. These are for deformed (TMT) bars in flexural members; laps in direct tension are twice as long.

Is the 50d lap rule correct?

It is close, not exact. By IS 456 the tension lap for Fe500 bars is 56.6d in M20 and 48.5d in M25, so 50d is slightly short in M20. With Fe415 it is 47.0d in M20. The lap shown on the structural drawings always governs.

Where should laps be placed?

Away from the points of highest stress, and staggered so that not all bars are lapped at the same section (IS 456 §26.2.5.1). In beams, bottom bars are usually lapped near the supports and top bars near mid-span.

Why is the compression lap shorter?

IS 456 allows 25% more bond stress in compression, so the compression development length is Ld ÷ 1.25. The lap must still be at least 24 bar diameters.

References

IS 456:2000 §26.2.1: development length Ld = φσs ÷ 4τbd, with σs = 0.87fy

IS 456:2000 §26.2.1.1: design bond stress τbd, increased by 60% for deformed bars and by 25% in compression

IS 456:2000 §26.2.5.1: flexural tension lap = Ld, at least 30φ; compression lap = Ld in compression, at least 24φ