Flight of Stairs | How Many Flight of Stairs per Floor | Design Criteria

A flight of stairs is an essential architectural element found in various buildings, from homes and offices to public spaces and skyscrapers. They provide vertical access between different levels, ensuring efficient movement and enhancing the overall functionality and aesthetics of a structure. This comprehensive guide will delve into the design criteria for stairs, explain how to determine the number of flights per floor, and shed light on crucial aspects of stairway design.

Design Criteria for Stairs:

1. Safety: Safety is paramount when designing stairs. Building codes and regulations set forth specific requirements regarding the dimensions, handrails, tread, riser height, and lighting. These standards ensure that stairs are safe and comfortable to use for people of all ages and abilities.
2. Width and Headroom: Stairs must have adequate width to accommodate the anticipated traffic flow. Additionally, sufficient headroom is crucial to prevent users from hitting their heads on the ceiling or other obstructions while ascending or descending the stairs.
3. Materials and Construction: Stairs can be constructed using various materials such as concrete, wood, metal, or a combination of these. The choice of material depends on factors like aesthetics, structural requirements, and budget considerations.
4. Visibility and Lighting: Proper lighting is essential to ensure users can see each step clearly, reducing the risk of tripping or falling. Good visibility is especially important for stairs located in dimly lit areas.
5. Handrails and Guardrails: Handrails provide support and balance to users, while guardrails prevent accidental falls from the open sides of the stairs. These elements must be designed and installed according to specific height and spacing requirements.
6. Stair Traffic and Building Use: The intended use of the building and the expected number of users influence the design of stairs. For high-traffic areas, wider and more robust stairs are necessary to handle the load.

Number of Flights per Floor:

The number of flights of stairs per floor depends on the total height between two consecutive floors and the height of each flight (riser height). To determine the number of flights, follow these steps:

1. Measure Total Height: Measure the vertical distance between the two floors for which the stairs are being designed. This height is typically measured from the top of one finished floor to the top of the next finished floor.
2. Calculate Riser Height: Divide the total height by the desired number of risers per flight. Building codes often specify a maximum riser height, usually between 6 to 8 inches, for residential and commercial buildings.
3. Round Up or Down: The result of the division will provide the number of risers needed. Round up to the nearest whole number. If the number of risers is not a whole number, adjust the riser height slightly to accommodate a whole number of risers.
4. Determine Number of Flights: The number of flights is equal to the number of risers minus one since there is no riser at the top landing.

Example:

Total height between two floors: 120 inches (10 feet) Desired riser height: 7 inches

Number of risers = Total height / Desired riser height = 120 inches / 7 inches ≈ 17.14 Round up to the nearest whole number: 18 risers

Number of flights = Number of risers – 1 = 18 – 1 = 17 flights

Conclusion:

Designing stairs involves adhering to essential criteria for safety, functionality, and aesthetics. Understanding the number of flights per floor and calculating the riser height accurately is vital to create a comfortable and user-friendly stairway. Always consult local building codes and work with experienced architects or engineers to ensure your stairs meet all necessary standards and provide a safe and visually appealing vertical circulation system in your building.