In industrial factory construction, the steel frame is considered the “backbone” of the entire structure. Choosing the right type not only affects load-bearing capacity and structural safety, but also directly impacts investment costs, construction progress, and future expansion capability.
Currently, the three most common types of steel frames used in factory buildings are Z frames, I frames, and built-up steel frames. Each type has distinct technical characteristics and is suitable for different scales and purposes. If the wrong option is selected, businesses may face overdesign, material waste, or difficulties in future renovation and expansion.
The article below provides an in-depth analysis of each frame type and compares them from multiple perspectives to help you select the most optimal steel frame solution for your factory project.
The steel frame is the primary structural system that bears all loads of the building, including:
Self-weight of the steel structure
Roof, wall cladding, and technical systems loads
Wind and seismic loads (if applicable)
Operational loads such as machinery, equipment, and overhead cranes
A properly designed steel frame system will:
Ensure long-term structural safety
Reduce unnecessary steel volume
Optimize foundation and substructure costs
Facilitate vertical expansion or future enlargement
Conversely, poor design or incorrect frame selection can significantly increase investment costs without delivering proportional performance benefits.
Z frames are typically used as roof purlins and wall girts within the steel frame system. Z purlins are cold-formed steel sections with a Z-shaped cross-section, thin thickness, and light weight.
Significantly reduce loads transferred to the main frame and foundation
Low cost and easy transportation and installation
Simple replacement and maintenance when needed
Not suitable as a primary load-bearing frame
Limited load-bearing and torsional resistance capacity
Highly dependent on bracing and connection systems
Z frames are suitable for:
Small to medium-sized factories
Buildings without overhead cranes
Projects prioritizing low initial investment costs
In practice, Z frames do not function independently; they are always combined with I frames or built-up frames to form a complete steel frame system.
I frames (or H frames) utilize hot-rolled steel sections with I-shaped or H-shaped cross-sections. They provide stable load-bearing performance in both vertical and horizontal directions.
Simple structural system, easy to design and construct
Good load-bearing capacity and high stability
Suitable for a wide range of factory types
Difficult to optimize cross-sections according to actual load demands
Steel weight increases rapidly for large spans
Potential material waste if overdesigned
I frames are commonly used for:
Medium-scale production factories
Warehouses and logistics buildings
Factories equipped with light to medium-duty overhead cranes
These frames are widely selected due to their balanced cost, durability, and fast construction capability.
Built-up steel frames are fabricated by welding steel plates (flanges and webs) into custom-designed cross-sections calculated specifically for each load-bearing position.
Cross-sections optimized precisely according to actual loads
Reduced steel volume compared to standard hot-rolled sections
Ideal for large spans and heavy load conditions
Higher fabrication costs
Requires certified manufacturing facilities
Strict quality control during production and welding
Built-up steel frames are optimal for:
Large-scale factory buildings
Facilities with heavy-duty overhead cranes
Projects requiring expansion or vertical extension
In the long term, built-up frames help optimize total investment costs, especially for large industrial developments.
| Criteria | Z Frame | I Frame | Built-up Frame |
|---|---|---|---|
| Structural Role | Secondary | Primary | Primary |
| Load-Bearing Capacity | Low | Medium – High | Very High |
| Material Optimization | Low | Medium | Very High |
| Suitable Span | Small | Medium | Large |
| Crane Compatibility | No | Yes (Light–Medium) | Yes (Heavy) |
| Long-Term Cost | Low | Medium | Optimized |
To choose the right steel frame system, businesses should consider the following questions:
Is the factory intended for manufacturing or warehousing?
Will it include overhead cranes? What is the required load capacity?
What is the current scale and future expansion plan?
Is the investment strategy short-term cost saving or long-term optimization?
Small factory with limited budget: I frame + Z frame
Standard factory: I frame
Large factory with heavy cranes: Built-up steel frame
There is no single steel frame solution suitable for every project. Selecting the right steel frame system requires careful technical analysis, understanding of functional requirements, and alignment with long-term investment strategy.
An optimally designed frame from the beginning not only ensures structural safety but also reduces costs, shortens construction time, and establishes a solid foundation for sustainable business growth in the future.
Learn more: Latest Cost Estimates for Pre-Engineered BuildingsAre you looking for a high-quality, durable, and cost-effective pre-engineered steel building solution?
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