---
title: "Staircase for municipal office (4900 × 2700 mm)"
subject: "Building Technology"
chapter: 5
key: "semester_6/building_technology:stair-municipal-079c"
source: https://www.bctengineer.com/q/semester_6/building_technology/stair-municipal-079c
site: BCT Engineering
---

# Staircase for municipal office (4900 × 2700 mm)

Building Technology · Chapter 5: Stair, lifts and escalators

- Asked in: 2079 Chaitra, 7 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/stair-municipal-079c
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-5

## Question

Define escalator. Design a staircase for municipal office with a stairwell space of 4900 mm × 2700 mm and 3000 mm floor to floor height. Also draw the plan and section of the designed staircase.

## Short answer

20 risers of 150 mm and treads of 300 mm; 2 flights x 10 risers; flight width 1.3 m.

## Answer

#### Escalator
An **escalator** is a moving stair: a continuous chain of steps driven by an electric motor, which carries a large number of people between floors at 0.5-0.65 m/s.
- Inclination 30 degrees (35 degrees max), step width 600, 800 or 1000 mm, capacity about 4500-9000 persons/hour.
- Parts: truss, steps, step chain, handrail, comb plate, drive motor, balustrade and safety switches.
- Used in shopping malls, airports, railway stations and metro stations, where heavy traffic moves continuously. It occupies more floor area than a lift, and an emergency stair is still needed in addition.

#### Design of staircase for municipal office
#### Given data and assumptions
- Stairwell (internal): 4.9 m x 2.7 m; floor-to-floor height $H = 3$ m; stair for a municipal office (public) building, RCC.
- Assumed riser $R = 150$ mm and tread $T = 300$ mm; flight width $b = 1.3$ m. A tread of 300 mm and a riser of 150 mm are taken because this is a public building.

#### Design
1. **Number of risers** $= H/R = 3/0.15 = 20$, adopt **20 risers**; exact riser $= 3/20 = 150$ mm.
2. **Flights:** a dog-legged stair has two equal flights, so each flight has 20/2 = 10 risers and 10-1 = 9 treads (the landing or upper floor acts as the last tread).
3. **Going of one flight** $= 9 \times 0.3 = 2.7$ m.
4. **Width:** two flights of 1.3 m side by side need $2b = 2.6$ m; the remaining $W - 2b = 2.7 - 2.6 = 0.1$ m is the gap between the flights.
5. **Landing:** a half-space landing 1.3 m x 2.7 m (full stairwell width) at height $= 10 \times 0.15 = 1.5$ m.
6. **Length check:** going + landing $= 2.7 + 1.3 = 4$ m $\le 4.9$ m, so it fits; the spare 0.9 m is kept as entry/exit space.
7. **Check:** $2R + T = 2 \times 150 + 300 = 600$ mm (within 550-650 mm); pitch $= \tan^{-1}(R/T) = 26.6^\circ$ (within 25-40 degrees).
8. **Waist slab:** effective span about 4 m, so depth $\approx$ span/20 $= 200$ mm; adopt a 200 mm thick waist slab (reinforcement to be designed separately). Provide a handrail 0.9 m high, 20-25 mm nosing and a non-slip finish.

#### Plan and section
```text
 +------------------------+---------+
 | FLIGHT 2  <<<<<<  UP   |         |
 | 9 treads               | LANDING |
 +------------------------+ (b x W) |
 | FLIGHT 1  >>>>>>  UP   |         |
 | 9 treads               |         |
 +------------------------+---------+
 <-------- going -------> <-- b -->
 (entry at left end of flight 1; arrows point up the stair)
```
```text
 SECTION (not to scale)
                          +---- upper floor 3 m
                    _____|
               ____|   flight 2
        ______|  landing
   ____|  flight 1
 _|
 ground floor +0.00
```

#### Summary
| Item | Adopted |
|---|---|
| Riser | 150 mm (20 nos.) |
| Tread | 300 mm |
| Flights | 2 flights x 10 risers |
| Width of flight | 1.3 m |
| Waist slab | 200 mm |

**Answer: 20 risers of 150 mm and treads of 300 mm; 2 flights x 10 risers; flight width 1.3 m.**

## Check yourself

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

1. What is an escalator?
   A. A lift in a shaft
   B. A moving stair of continuous steps driven by a motor, 0.5-0.65 m/s
   C. A ramp
   D. A fixed stair
   Answer: B. It is a continuous chain of motor-driven steps. (Key point: Escalator)

2. Why tread 300 mm and flight width 1.3 m here?
   A. Residential rules
   B. Public building needs bigger tread/width than residential
   C. To reduce risers
   D. To fit a lift
   Answer: B. A public building has heavier traffic, so larger tread and width are taken. (Key point: Public building proportions)

3. Going of a flight with 9 treads of 300 mm is
   A. 2.25 m
   B. 2.7 m
   C. 3.0 m
   D. 3.3 m
   Answer: B. 9 x 0.3 = 2.7 m. (Key point: Going)

4. Effective span 4 m, depth about span/20 gives
   A. 100 mm
   B. 150 mm
   C. 200 mm
   D. 400 mm
   Answer: C. 4000/20 = 200 mm. (Key point: Waist slab)

## Related in Building Technology

- [Dog-legged RCC stair design for 3 m floor height](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Astair-dog-3m-assume) — Building Technology, chapter 5, asked 3×
- [Open-well staircase (6.0 m × 3.5 m hall)](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Astair-064j) — Building Technology, chapter 5
- [Plan and vertical section of panelled door](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apanelled-door-plan-section) — Building Technology, chapter 6
- [RCC dog-legged stair for office building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Arcc-stair-office-building) — Building Technology, chapter 5
- [Staircase for public building (5.5 m × 6.5 m)](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Astair-public-5p5x6p5) — Building Technology, chapter 5
- [Quarter turn stair, 2.1 m by 5 m](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aquarter-turn-stair-2p1m-wide-well) — Building Technology, chapter 5

## Related in other subjects

- [Preliminary estimate: six-storey office, 3000 m²](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-six-storey-3000) — Estimating and Costing, chapter 3
- [Guide bund with plan, section, nose; 2500 m3/s](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Aguide-bund-q2500-bed755) — Irrigation and Drainage Engineering, chapter 6
- [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
- [Slab panel 2 for BM and SF (floor plan)](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aslab-panel-2-for-bm-and) — Design of RCC Structure, chapter 9