Amogh N P
✦ In loving memory of Amogh N P — Architect · Designer · Visionary ✦
An Indian construction site with reinforced concrete column cages rising from the plinth.
Unit IIBuilding Materials & Construction II

RCC Columns

The vertical load path — vertical bars held by ties.

≈ 40 min

The column gathers the building's load and carries it down to the footing. It looks simple — a box of concrete — but its reinforcement and its setting-out are exacting. This lesson covers the column families, the marking layout and the bars and ties inside.

Learning objectives

By the end of this lesson you will be able to — mapped to the course outcomes for Building Materials & Construction II:

1
CO3 · Understand

Distinguish tied and spiral columns and their shapes.

2
CO3 · Apply

Set out a column marking layout from the structural grid.

3
CO3 · Apply

Detail column reinforcement — vertical bars and lateral ties.

4
CO3 · Understand

Apply the IS 456 rules for minimum steel, bar size and tie spacing.

The families

Tied & spiral columns

Columns are reinforced in two ways — separate ties, or a continuous spiral. Select a topic.[1]

Tied & spiral

Columns come in two reinforcement families. A TIED column has its vertical bars held by separate closed loops (ties / links) at intervals — the usual square or rectangular column. A SPIRAL column wraps the vertical bars in a continuous helix — usual for circular columns, and a little tougher under overload.[1]

Two column families Tied bars held by separate ties Spiral bars wrapped in a continuous helix
DiagramA tied column and a spiral column compared
Column section cover • vertical (longitudinal) barscarry the compression load• lateral tie (the loop)stops the bars buckling, confines concrete IS 456: 0.8–6% steel, ≥4 bars (rectangular), ≥12 mm; ties at the least of side / 16·dia / 300 mm.
DiagramA square column section showing four corner bars, a tie and the cover
Setting out

Marking from the grid

Before any steel, the columns are set out on site from the structural grid — get this wrong and the whole frame is out.[2]

Mark the columns from the grid ABC12 Each column is set out at its grid intersection (A1, B1…) — a marking error misaligns the whole frame.
DiagramColumn positions marked out on a grid before steelwork
Steel, bars & ties

The IS 456 rules

IS 456 fixes the limits that keep a column safe and buildable.[3, 4]

RuleValueNote
Longitudinal steel0.8% – 6% of sectionMinimum for safety; maximum to avoid congestion.
Minimum bars4 (rectangular) · 6 (circular)One in each corner / round the spiral.
Minimum bar size12 mmSmaller bars buckle too easily.
Tie spacing (max)least of {side, 16·dia, 300 mm}Closer ties confine better.
A close-up of a column cage — vertical bars held by square ties.
PhotoA close-up of a column cage — vertical bars held by square ties.
Column positions marked out on a slab from the grid lines.
PhotoColumn positions marked out on a slab from the grid lines.
Timber and steel formwork boxing a column ready for pouring.
PhotoTimber and steel formwork boxing a column ready for pouring.
An Indian construction site with reinforced concrete column cages rising from the plinth.
PhotoAn Indian construction site with reinforced concrete column cages rising from the plinth.
Check your understanding

Self-assessment

1. In a tied column, the lateral ties mainly:

2. Per IS 456, the minimum longitudinal steel in a column is:

3. ‘Column marking’ on site means:

In a nutshell

Recap

Columns are tied (links at intervals) or spiral (continuous helix, usually circular).
Mark the columns from the grid before any steel — an error here misaligns the whole frame.
Vertical bars carry load; lateral ties stop them buckling and confine the concrete.
IS 456: 0.8–6% steel, ≥4 bars (rect) / 6 (circular), ≥12 mm; tie spacing = least of side / 16·dia / 300 mm.
The codes

References & further reading

  1. [1]RCC columns — tied vs spiral; longitudinal bars and lateral ties; detailing. Civil-engineering overview. https://theconstructor.org/structural-engg/reinforced-concrete-column/
  2. [2]Column marking / setting out from the structural grid on site. Construction practice. https://civiconcepts.com/blog/column-layout
  3. [3]IS 456:2000 column reinforcement — 0.8–6% steel, min 4/6 bars, tie pitch (Cl. 26.5.3). EduRev / BIS. https://law.resource.org/pub/in/bis/S03/is.456.2000.pdf
  4. [4]Concrete grades (M20/M25 = fck N/mm²) and steel grades (Fe415/Fe500 = yield N/mm²). Overview. https://testbook.com/question-answer/the-grade-of-concrete-m20-means-that-characteristi--671af1098de8c6fcb3276b9a

Further reading

  • BIS (2000). IS 456: Plain and Reinforced Concrete — Code of Practice. New Delhi: BIS — Clause 26.5 (column detailing).
  • BIS (1987). SP 34: Handbook on Concrete Reinforcement and Detailing. New Delhi: BIS.
  • Pillai, S.U. & Menon, D. (2017). Reinforced Concrete Design (3rd ed.). New Delhi: McGraw-Hill Education.

Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.