--- title: "Quarter turn stair, 2.1 m by 5 m" subject: "Building Technology" chapter: 5 key: "semester_6/building_technology:quarter-turn-stair-2p1m-wide-well" source: https://www.bctengineer.com/q/semester_6/building_technology/quarter-turn-stair-2p1m-wide-well site: BCT Engineering --- # Quarter turn stair, 2.1 m by 5 m Building Technology · Chapter 5: Stair, lifts and escalators - Asked in: 2080 Chaitra, 5 marks - Video: [Quarter Turn Stairs with Landing Example #1](https://www.youtube.com/watch?v=Y7LdbloRY5Y) — Luc Lapierre - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/quarter-turn-stair-2p1m-wide-well - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-5 ## Question Design a quarter turn staircase for a residential building having a stairwell of 2.1m x 5m and floor height 3m. Draw plan and section. ## Short answer 18 risers of 166.7 mm and treads of 240 mm; flights of 12 and 6 risers; flight width 0.9 m. ## Answer #### Given data and assumptions - Stairwell (internal): 5 m x 2.1 m; floor-to-floor height $H = 3$ m; stair for a residential building, RCC. - Assumed riser $R = 167$ mm and tread $T = 240$ mm; flight width $b = 0.9$ m. The narrow 2.1 m width limits the cross flight, so a riser of about 167 mm and a tread of 240 mm (slightly less than the usual 250 mm) are taken; the maximum riser for dwellings is 175 mm. #### Design 1. **Number of risers** $= H/R = 3/0.167 = 18$, adopt **18 risers**; exact riser $= 3/18 = 166.7$ mm. 2. **Flights:** a quarter-turn stair has a square quarter landing. Take flight 1 = 12 risers (11 treads) and flight 2 = 6 risers (5 treads); total 12 + 6 = 18 risers. 3. **Goings:** flight 1 $= 11 \times 0.24 = 2.64$ m; flight 2 $= 5 \times 0.24 = 1.2$ m. 4. **Quarter landing:** 0.9 m x 0.9 m at height $= 12 \times 0.1667 = 2$ m. 5. **Fit along the length:** $2.64 + 0.9 = 3.54$ m $\le 5$ m. 6. **Fit along the width:** $0.9 + 1.2 = 2.1$ m $\le 2.1$ m. 7. **Check:** $2R + T = 2 \times 166.7 + 240 = 573$ mm (within 550-650 mm); pitch $= \tan^{-1}(R/T) = 34.8^\circ$ (within 25-40 degrees). 8. **Waist slab:** effective span about 3.54 m, so depth $\approx$ span/20 $= 177$ 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 +----+--------------------+ | F2 | | | ^ | | | ^ | (hall) | +----+--------------------+ |LAND| <<<<<<<<<<<< F1 UP | +----+--------------------+ F1 = 12 risers (starts at the right end), quarter landing, F2 = 6 risers (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 | 166.7 mm (18 nos.) | | Tread | 240 mm | | Flights | flights of 12 and 6 risers | | Width of flight | 0.9 m | | Waist slab | 200 mm | **Answer: 18 risers of 166.7 mm and treads of 240 mm; flights of 12 and 6 risers; flight width 0.9 m.** ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. H = 3 m, R about 167 mm. How many risers? A. 12 B. 15 C. 18 D. 20 Answer: C. 3/0.167 is about 18 risers (exact 166.7 mm). (Key point: Risers) 2. How are the 18 risers divided in the quarter-turn stair? A. 9 and 9 B. 12 and 6 C. 10 and 8 D. 15 and 3 Answer: B. Flight 1 has 12 risers and flight 2 has 6, with a quarter landing between. (Key point: Flight split) 3. Quarter landing is at what height? A. 12 x 0.167 = 2 m B. 6 x 0.167 = 1 m C. 1.5 m D. 3 m Answer: A. It is reached after 12 risers: about 2 m. (Key point: Landing height) 4. Why is the width check 0.9 + 1.2 = 2.1 m important? A. Landing plus flight 2 going must fit within the 2.1 m well width B. It gives riser height C. It gives waist slab D. It is the handrail height Answer: A. Landing width plus the going of flight 2 exactly fills the narrow well. (Key point: Width fit) ## Related in Building Technology - [Quarter turn stair, 5.5 m by 4.0 m](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aquarter-turn-stair-residential-lobby) — Building Technology, chapter 5 - [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× - [Vertical circulation elements; RCC dog-legged stair](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Astair-circulation-068ba) — 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 - [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 - [Dog-legged stair design with elevators and ramp](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Astair-078c) — Building Technology, chapter 5 ## Related in other subjects - [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 - [Preliminary estimate: residential, 500 m² carpet](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-residential-500) — Estimating and Costing, chapter 3 - [Quantity sheet and abstract for residential building](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aquantity-sheet-abstract-residential) — Estimating and Costing, chapter 2 - [Principal MI and axes of quarter-circle/triangle section (2078 Bhadra)](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aprincipal-mi-2078b) — Strength of Materials, chapter 2