Design Drawing of Stairs for Prefabricated Slab Houses

Currently, there is no direct and complete design drawing of stairs for prefabricated slab houses, but design key points can be provided based on relevant design information.

Key Points for Designing Stair Components

• Flight: Usually, a plate-type flight is adopted, which is an inclined member connecting two platforms at different elevations. When designing, its inclination angle should be considered. A common slope ratio is 1:2 to ensure walking comfort and safety.
• Landings: There are intermediate landings and floor landings. Intermediate landings are located between two floors, while floor landings are level with the floor surface. The width of landings should meet usage requirements. The width of intermediate landings should not be less than that of the flight, and the width of floor landings should not be less than the clear width of the flight and should be at least 1.2m to facilitate personnel stopping and turning.
• Balustrades and Handrails: They are installed at the edges of flights and landings for safety protection. When the width of the flight is not large, handrails can be installed only on the open side of the flight. When the width of the flight is relatively large (more than three streams of people, 1650mm wide), wall-mounted handrails should be installed on the non-open side. When the width of the flight is very large (more than four streams of people, 2200mm wide), an intermediate handrail should be installed in the middle of the flight. The height of handrails should generally not be less than 0.9m. When the open height of the flight is greater than 24m, the height of handrails should not be less than 1.05m.

Key Points for Selecting Stair Forms

• By Combination Form: There are various options, such as straight single-run stairs, straight multi-run stairs, and parallel double-run stairs. Among them, spiral stairs are not suitable as evacuation stairs, and curved stairs can be used but have dimensional requirements. Prefabricated slab houses can select appropriate combination forms according to spatial layout and usage requirements. Parallel double-run stairs are relatively common, which can save space and are convenient to use.
• By Structural Form: There are beam-type, plate-type, cantilever, suspended, and wall-bearing forms. Prefabricated slab houses generally adopt plate-type stairs, which have a simple structure, are convenient for construction, and are suitable for the installation and use of prefabricated slabs.

Key Points for Designing Stair Dimensions

• Tread Dimensions: A tread height of 150mm is appropriate and should not be higher than 175mm. A tread width of 300mm is appropriate and should not be narrower than 260mm. To increase walking comfort, the treads are often overhanging by 20 - 30mm. At the same time, the relationships of 2h + b = 600 - 620mm or h + b = 450mm should be met, and the number of treads is generally between 3 and 18.
• Flight Dimensions: The width of the flight is determined according to the number of streams of people required for emergency evacuation. Each stream of people is 550mm wide, 1100mm for two people, and 1650mm for three people. The clear width of evacuation stair flights should not be less than 1100mm. The length of the flight is calculated according to the number of treads and the tread width.