---
title: "Detailing of reinforcement in staircases"
subject: "Design of RCC Structure"
chapter: 9
key: "semester_7/design_of_rcc_structure:detailing-of-reinforcement-in-staircases"
source: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/detailing-of-reinforcement-in-staircases
site: BCT Engineering
---

# Detailing of reinforcement in staircases

Design of RCC Structure · Chapter 9: Design of slabs and staircase

- Asked in: 2068 Baisakh (old course), 5 marks
- Video: [Reinforcement of Staircase Explained in Detail](https://www.youtube.com/watch?v=vX9UXbqUGek) — Engineering Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/detailing-of-reinforcement-in-staircases
- Whole chapter: https://www.bctengineer.com/md/semester_7/design_of_rcc_structure/chapter-9

## Question

Explain about detailing of reinforcement in staircases.

## Short answer

Main bars at bottom parallel to slope, anchored Ld; distribution bars 8 mm @ 150-200 c/c; top negative steel about 50% of mid-span steel at supports. At re-entrant corner, flight and landing bars are crossed and anchored separately, not bent round the corner. Cover 15-20 mm, spacing limits 3d/300 mm.

## Answer

Detailing of a staircase means the arrangement of bars in the flight and landing so that the tensile stresses are resisted, the bars are properly anchored, and the cover and spacing are as per IS 456.

#### Flight (waist slab)
- **Main bars** are placed at the bottom of the waist slab, parallel to the slope, usually 10 or 12 mm diameter at 100-150 mm c/c. They run to the supports and are anchored for the full development length $L_d$, with a bend if there is little space.
- **Distribution bars** (8 mm @ 150-200 c/c) are placed perpendicular to the main bars to hold them in place and resist shrinkage and temperature stresses; minimum steel is 0.12% of the gross area for HYSD bars (Fe415/Fe500).
- **Top (negative) steel**: where the flight is built into a wall or beam, or is continuous over a landing, top bars of about 50% of the mid-span steel are placed over the support and extended $0.1 l$ to $0.3 l$ into the span.
- The thickness of the waist slab is measured perpendicular to the slope; the steps themselves are not counted as structural.

#### Landing
- The landing is an ordinary slab; its main bars span in the direction in which the landing spans, and bars from the flight are carried into it for anchorage.
- When the flight and landing are in different planes, the bars at the **re-entrant corner** are not bent continuously round it. Both sets of bars are crossed, and each is extended $L_d$ beyond the intersection, because a bent tension bar would try to straighten and break out the concrete cover.

```text
          landing           flight
   ____________________
  |   ____________    \
  |  |  main bars  \   \  distribution
  |__|______________\___\ bars across
     <-- Ld --> crossing bars at the
                 internal corner
```

#### General rules
- Minimum cover 15-20 mm (mild exposure); spacing of main bars not more than $3d$ or 300 mm, and of distribution bars not more than $5d$ or 300 mm.
- In a dog-legged stair, the bars of the two flights are lapped or anchored where they meet the common landing.
- Stirrups are not required in the slab when $\tau_v \le k\tau_c$.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Where are the main bars and how are they anchored?
   A. At the bottom along the slope, anchored for Ld, with a bend if space is short
   B. At the top, perpendicular to the slope
   C. At mid-depth, with no anchorage
   D. Only in the landing
   Answer: A. Main bars are at the bottom parallel to the slope and continue to the supports for the full development length. (Key point: Main bars)

2. What top steel is given where a flight is built into a wall or continuous over a landing?
   A. None
   B. About 50% of mid-span steel, extended 0.1 l to 0.3 l into the span
   C. 200% of mid-span steel
   D. Same as distribution steel only
   Answer: B. Partial fixity gives negative moment, resisted by top bars of about half the mid-span steel. (Key point: Top steel)

3. How are bars treated at the re-entrant corner between flight and landing?
   A. Bent continuously round the corner
   B. Crossed and anchored by lapping Ld beyond the intersection
   C. Left out
   D. Welded together
   Answer: B. A continuous bent bar would straighten under tension and burst the concrete, so two sets are crossed and anchored. (Key point: Re-entrant corner detail)

4. How is the depth of the waist slab measured?
   A. Vertically through the step
   B. Perpendicular to the slope, ignoring the steps as structure
   C. Along the horizontal
   D. Including the step height
   Answer: B. Depth is perpendicular to the incline; steps are not counted as structural. (Key point: Waist slab depth)

## Related in Design of RCC Structure

- [Ductile detailing of columns, confining steel](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aductile-detailing-of-columns-confining-steel) — Design of RCC Structure, chapter 12, asked 4×
- [Column 350x350, 1440 kN, ductile detailing](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Acolumn-350x350-1440-kn-ductile-detailing) — Design of RCC Structure, chapter 10, asked 2×
- [Staircase design concept and detailing](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Astaircase-design-concept-and-detailing) — Design of RCC Structure, chapter 9