Designing Outdoor Steel Structure Stairs: A Practical Guide for Contractors and Distributors
When a project calls for an outdoor steel staircase, detailed engineering drawings are not always available upfront. In many cases, clients have site-specific requirements—length, width, load capacity, and installation conditions—but rely on experienced suppliers to recommend the right components.
At NJMM, we frequently work with contractors who need practical guidance to select Stair Treads, confirm overall dimensions, and plan for handrails and landings. This post outlines a straightforward approach to designing outdoor steel stairs when detailed drawings are not provided, based on the key data clients can supply.
Key Parameters Clients Can Provide
Even without full structural drawings, most clients can provide essential information to initiate the design process. The following parameters are sufficient to recommend suitable stair tread models and confirm the main structural dimensions.
1. Overall Length and Height
The total vertical rise (height from ground to the top landing) and the horizontal run available determine the staircase inclination. For outdoor steel stairs, a comfortable and code-compliant inclination is typically around 30° to 35°, with a maximum of 45° for occasional access . The riser height (step height) should generally be less than 200mm, with a popular size around 180mm, and all steps must be consistent .
2. Stair Width and Load Requirements
The required stair width depends on traffic flow and application. Common tread widths are 700mm, 800mm, and 900mm, with the maximum recommended being 1200mm . For single-person passage, the clear width between stringers should not be less than 600mm . For two-way traffic, 1200mm is recommended . Load capacity is also critical, with general duty applications requiring a uniformly distributed load (UDL) of 5.0 kN/m² and a concentrated load of 1.0 kN .
3. Presence of Landings or Corners
Any change in direction or intermediate landing requires additional planning. Landings need their own Steel Grating Platforms and handrails, and the dimensions must be carefully coordinated to maintain a safe and functional layout.
Recommended Stair Tread Selection
Based on the client’s load and width data, NJMM can recommend a suitable tread model. The most common Steel Grating Treads are Type 1 (welded installation, without nosing) and Type 3 (welded installation, with nosing) . For outdoor applications, serrated bearing bars are strongly recommended to enhance slip resistance, especially given the potential for rain and moisture .
Critical Design Data: Handrails and Side Stringers
The overall length, height, and inclination directly affect the design of handrails and side stringers. Accurate calculations are essential to ensure safety and code compliance.
Handrails
Outdoor steel stairs require handrails on at least one side, with a height of no less than 1050mm . As a best practice, the design height is often set at 1100mm above the pitch line or tread surface . Handrails must be able to withstand a lateral load of at least 0.36 kN/m for general duty applications .
Side Stringers
The stringer size must be appropriate for the span and load. For the treads themselves, the bearing bar thickness should not be less than 3mm, with 5mm being the recommended standard . For heavy-duty or high-traffic stairs, heavier bearing bar sections like G255/30/100FG are often specified .
Landings and Platforms
If the staircase has an intermediate landing or a corner, additional steel grating platform sections are required. These platforms must be designed for the same live loads as the stairs and should be equipped with handrails and toe plates as per safety standards . Toe plates should be at least 100mm high to prevent objects from falling off the edge .
Summary of Key Design Considerations| Parameter | Key Consideration |
| Stair Inclination | 30°–35° is standard; maximum 45° for occasional access |
| Stair Inclination | <200mm (≈180mm typical) |
| Tread Width | 600mm (minimum); 700–900mm (common); 1200mm (maximum) |
| Handrail Height | ≥1050mm (outdoor) |
| Toe Plate Height | ≥100mm |
| Load (General Duty) | UDL 5.0 kN/m²; Concentrated 1.0 kN (per 300×300mm) |
| Tread Type | Galvanized steel grating recommended for outdoor use |
| Connection | Welded or bolted, depending on installation requirements |
Conclusion
Designing an outdoor steel staircase does not always require a complete engineering drawing set from the client. By confirming a few key parameters—total height, length, width, load, and the presence of landings—experienced manufacturers like NJMM can recommend the right tread types, confirm inclination, and ensure proper handrail and stringer design.
For distributors and contractors, this practical approach simplifies the procurement process and ensures that the final product is safe, durable, and compliant with relevant standards. Contact NJMM to discuss your next outdoor stair project and let our engineering team guide you through the selection and design process.