A stair turning one right angle is known as
🔬 Understanding Staircase Geometry
Staircases are classified based on their shape and the way they change direction. The "turn" of a stair refers to the total angle of direction change from the bottom of the stair to the top. A right angle is a 90-degree turn.
Quarter-Turn Stairs: As the name implies, this type of staircase makes a single turn of 90 degrees (a quarter of a full 360-degree circle). This turn can be achieved with a small landing or with angled steps called winders. They are commonly used when the available length for the staircase is limited, but there is sufficient width.
⚖️ Detailed Analysis of the Options
Let's examine the degree of turn for each type of staircase mentioned.
(c) Quarter-Turn Stairs
Why it's correct: This stair changes the direction of the flight by one right angle (90°). This is the precise definition given in the question.
(a) Dog-Legged Stairs
Why it's incorrect: This is a type of Half-Turn (180°) stair. It consists of two parallel flights running in opposite directions, connected by a landing. There is no space between the two flights.
(b) Half Turn Stairs
Why it's incorrect: This is a general category for any stair that turns 180°. While a dog-legged stair is a half-turn stair, the question specifically asks for a single right-angle (90°) turn.
(d) Open Newel Stairs
Why it's incorrect: This is another type of Half-Turn (180°) stair. Unlike a dog-legged stair, it features a well or opening between the two flights, making it feel more spacious. It still completes a 180° turn.
📋 Glossary of Stair Turn Types
Understanding the different classifications of stair turns is key to selecting the right design for a space.
- Quarter-Turn (90°): The flight turns at a right angle, to the left or right. Ideal for corners.
- Half-Turn (180°): The direction of travel reverses. Dog-legged and Open Newel are the most common types. Very efficient for multi-story buildings.
- Three-Quarter Turn (270°): The stair turns through three right angles. Often used to access a higher level in a compact space.
- Continuous Stairs: These stairs have no intermediate landings or newel posts and can be circular or spiral in shape.