--- title: "Elements and types of stair" subject: "Building Technology" chapter: 5 key: "semester_6/building_technology:stair-elements-types" source: https://www.bctengineer.com/q/semester_6/building_technology/stair-elements-types site: BCT Engineering --- # Elements and types of stair Building Technology · Chapter 5: Stair, lifts and escalators - Asked in: 2071 Magh, 8 marks; 2070 Magh (asked 2 times) - Video: [Stair Components and Terminology](https://www.youtube.com/watch?v=wGQvUw_aApQ) — Buildsum - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/stair-elements-types - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-5 ## Question Describe the essential elements of stair. Illustrate the types of stair with sketches. ## Short answer Essential stair elements include tread, riser, nosing, flight, landing, going, rise, waist slab/stringer, soffit, handrail, baluster, newel post, headroom, winder, and pitch line. Types: straight, quarter-turn, dog-legged, open-well, half-turn, three-quarter turn, bifurcated, geometrical, and spiral. ## Answer A **stair** is a set of steps (a series of risers and treads) that connects floors at different levels, giving access from one storey to another, usually with landings and a balustrade. #### Essential elements of a stair A stair has the following essential elements: - **Step:** one riser plus one tread; steps are the basic unit. - **Tread and riser:** the tread is the horizontal surface (250-300 mm), the riser the vertical face (150-175 mm). - **Nosing:** the rounded projecting edge of the tread (about 25 mm). - **Flight:** an unbroken series of steps between landings (3 to 12 steps). - **Landing:** a level platform at the ends of a flight or between flights; quarter-space or half-space. - **Going and rise:** the horizontal and vertical measurements of a step or flight. - **Waist slab / stringer:** the inclined slab or beam which supports the steps. - **Soffit:** the underside of the flight. - **Handrail, baluster and newel post:** the balustrade that protects the open sides; the handrail is about 0.9 m high. - **Headroom:** the clear height above the steps (minimum about 2.0-2.2 m). - **Winder:** a tapered step used to turn the stair in a restricted space. - **Pitch line:** an imaginary line joining the nosings; its angle with the horizontal is the pitch. ```text handrail /| baluster newel /_|__ | | nosing riser |____|__ tread ______| going <---> ``` #### Types of stair (with sketches) | Type | Description | |---|---| | Straight (single flight) | One continuous flight between two floors, no turn | | Quarter-turn | Direction changes by 90 degrees at a quarter-space landing | | Dog-legged | Two flights in opposite directions with a half-space landing and no well between the flights | | Open-newel / open-well | Two or more flights with a clear well between them | | Half-turn (two-flight) | Turn of 180 degrees, either dog-legged or open-well | | Three-quarter turn | Three flights turning through 270 degrees around a well | | Bifurcated (branching) | One wide flight splits into two narrower flights at a landing | | Geometrical | Curved (circular or elliptical) flights round an open well, without newel posts; continuous handrail | | Spiral / circular (helical) | Winder steps radiating round a central post or on a circular plan; saves space | ```text Straight Quarter turn Dog-legged Open well | | | | |_____ |>>>>>| |>>>>>| | | | | | |<<<<<| | | | | | |__| |_____| |<<<<| (well) Spiral (central post) Bifurcated ___ _|_ / o \ | | \___/ \ / ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which pair is correct for typical dimensions? A. Tread 250-300 mm, riser 150-175 mm B. Tread 150-175 mm, riser 250-300 mm C. Tread 100 mm, riser 400 mm D. Both 300 mm Answer: A. Tread is horizontal; riser is the vertical face. (Key point: Tread and riser) 2. What is a flight of stairs? A. The platform at turns B. An unbroken series of steps between landings C. The projecting edge of a tread D. The underside of the stair Answer: B. A flight has 3 to 12 steps without a break. (Key point: Flight) 3. What characterises a dog-legged stair? A. A single straight flight B. Flights with a clear well between them C. Two flights in opposite directions with a half-space landing and no well D. Steps radiating around a newel Answer: C. The open-well type has a well; dog-legged does not. (Key point: Dog-legged) 4. What is a bifurcated stair? A. Two flights joined into one B. A 270 degree turn stair C. A single-flight stair D. One wide flight splitting into two narrower flights at a landing Answer: D. It branches at a landing into two flights. 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