| Primary value | 200 mm c / c (typical) (code limit: min(B, 16 ϕ, 300 mm) — IS 13920 hinge: min(B/4, 100 mm)) |
| Applies to | Tied RCC columns (rectangular or square section) · Columns designed to IS 456 in non-plastic-hinge zones |
| Exceptions | IS 13920 — confining hoops at plastic hinge zone (lo) → min(B/4, 100 mm), but ≥ 75 mm |
| Plastic hinge zone length lo → max(D, height/6, 450 mm) from each end | |
| Spirally reinforced column pitch → min(B/6, 75 mm) | |
| Minimum tie diameter → 6 mm or ϕ/4, whichever larger | |
| Measured as | Centre-to-centre vertical spacing of lateral ties (also called rings or hoops). B = least lateral dimension of the column, ϕ = diameter of smallest longitudinal bar. |
| Source | IS 456 — Clause 26.5.3.2 (c) ✓ Verified |
68 related items across IS codes, knowledge articles, design rules, maps and tools
Lateral ties prevent the longitudinal bars from buckling outward under axial load. The 16ϕ limit is set so that the tied bar can't bow between ties more than its yield curvature; the 300 mm cap covers wide columns where 16ϕ is too generous. IS 13920's plastic hinge confinement is what lets columns survive earthquake reversals without spalling.
Most residential columns get 8 mm ties at 200 mm c/c outside the plastic hinge zone and 100 mm c/c inside it — acceptable for Fe500 main bars up to 25 mm diameter. Skipping the tighter spacing at column ends is a common detailing error in non-seismic-aware drawings.