---
title: "Stair terms (baluster, nosing, soffit) and types"
subject: "Building Technology"
chapter: 5
key: "semester_6/building_technology:stair-terms-types-079a"
source: https://www.bctengineer.com/q/semester_6/building_technology/stair-terms-types-079a
site: BCT Engineering
---

# Stair terms (baluster, nosing, soffit) and types

Building Technology · Chapter 5: Stair, lifts and escalators

- Asked in: 2079 Asoj, 7 marks
- Video: [Technical Terms in Stairs | Stairs | Building Construction](https://www.youtube.com/watch?v=V25plrWEH1k) — SGK Online Education
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/stair-terms-types-079a
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-5

## Question

Define the term baluster, nosing, soffit and pitch with sketch. What are the types of stair? Explain any two with sketch.

## Short answer

Baluster: vertical post supporting handrail. Nosing: rounded tread edge projecting 25 mm. Soffit: underside of flight. Pitch: angle of inclination (25-40 deg). Types: straight, quarter-turn, dog-legged, open-well, half-turn, three-quarter turn, bifurcated, geometrical, spiral. Dog-legged: two opposite flights with half-space landing, no well. Quarter-turn: 90 deg turn at landing.

## Answer

#### Terms
- **Baluster:** a vertical post (small column) that supports the handrail and fills the gap between the handrail and the steps.
- **Nosing:** the rounded edge of the tread that projects (about 25 mm) beyond the riser; it increases the foot space and gives a neat edge.
- **Soffit:** the underside (lower surface) of a flight or landing, usually plastered.
- **Pitch:** the angle of inclination of the stair, measured between the line joining the nosings (pitch line) and the horizontal; $\tan\theta = R/T$, usually 25-40 degrees.

```text
        handrail
        |  baluster
        |  |
        |  |__ nosing
     ___|__|
  riser |  tread
  ___ __|
 pitch angle  soffit below
```
#### Types of stair
| 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 |

#### Two types explained
**1. Dog-legged stair:** two straight flights run in opposite directions, connected by a half-space landing. There is no well between the flights, so in section they look like a dog's leg. It takes little floor area and is very common in houses and public buildings.
```text
 +----------+-------+
 | <<< UP   |       |
 +----------+  L    |
 | >>> UP   |       |
 +----------+-------+
```
**2. Quarter-turn stair:** the direction of the stair changes by 90 degrees at a quarter-space (square) landing; it is used where the stair turns at a corner of a hall.
```text
 +-----+
 | F2  |
 | ^   |
 +-----+------------+
 | L   | F1 <<<<<   |
 +-----+------------+
```

## Check yourself

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

1. What is the stair pitch?
   A. Angle between the pitch line (through nosings) and the horizontal
   B. Angle between riser and tread
   C. Height of handrail
   D. Slope of the landing
   Answer: A. tan(theta) = R/T, usually 25-40 degrees. (Key point: Pitch)

2. What is the soffit?
   A. Top of the tread
   B. Underside of a flight or landing
   C. Rounded tread edge
   D. Post at the turn
   Answer: B. Soffit is usually plastered. (Key point: Soffit)

3. What does a baluster do?
   A. Carries the stair load to the wall
   B. Forms the turning step
   C. Supports the handrail from the steps
   D. Provides headroom
   Answer: C. It is a vertical post between steps and handrail. (Key point: Baluster)

4. When is a quarter-turn stair used?
   A. Direction reverses 180 degrees
   B. Stair is a single flight
   C. Steps radiate around a newel
   D. Direction changes by 90 degrees at a quarter-space landing
   Answer: D. It is used where the stair turns at a corner. (Key point: Quarter turn)

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