Maximum permitted spacing of stirrups in beams and ties (transverse reinforcement) in columns, per IS 456 for ordinary detailing and IS 13920 for ductile (seismic) detailing. Spacing must satisfy ALL applicable rules — pick the smallest value.
Column Ties — IS 13920 (Ductile/Seismic)
Confining zone lo = max(D, hclear/6, 450 mm) at top & bottom of column
| Rule | Value | Applies | Note |
|---|
| Tie spacing in lo zone | min(B/4, 6 × dlong, 100 mm) | Confining zone | But ≥ 75 mm |
| Tie spacing outside lo zone | ≤ ½ × least lateral dimension | Mid-height of column | Cl 7.4.6(b) |
| Cross-tie hook | 135° one end + 90°+6d other end | Allowed | Or 135° both ends |
| Spacing of cross-ties along long bar | ≤ 300 mm | Cl 7.4.4 | — |
| Special confinement at footings | Continue lo into footing | Anchorage zone | — |
Notes
• When IS 13920 applies, IS 456 spacing limits are SUPERSEDED — use the smaller of the two
• ALWAYS apply 'least of all rules' — never just pick one criterion
• Provide a hook on every tie — open ties slip under cyclic load
• First stirrup/tie must be within 50 mm of the support face (good practice)
• Tie diameter ≥ ¼ of main bar diameter is the controlling rule for thick columns
• For columns with ≥ 4% steel, all bars must be tied (no skipping alternate bars)
• Stirrup bending must use the correct hook — d2 lap is unsafe under cyclic loading
• BBS (bar bending schedule) must explicitly call out 135° hook for all seismic stirrups