Cold-Formed Steel: A Guide for Residential and Light Commercial Projects

Introduction

In the ever-evolving construction industry, new materials and techniques are constantly being introduced to meet the demand for sustainable and efficient building solutions. One such material that has gained significant popularity in recent years is cold-formed steel.

This article serves as a comprehensive guide for structural engineers who are interested in using cold-formed steel as a structural material in residential and light commercial projects. We will explore what cold-formed steel is, its benefits, its applications in building construction, and key considerations for engineers

What is Cold-Rolled Steel?

Cold-formed steel refers to steel products that are formed by cold-working processes, such as rolling or pressing, at room temperature.

Unlike hot-rolled steel, which is shaped while it is heated, cold-formed steel is manufactured at lower temperatures, resulting in distinct mechanical properties.

Cold-formed steel exhibits excellent strength-to-weight ratio, dimensional stability, and uniformity in shape and size. These properties make it an attractive choice for a wide range of applications in the construction industry, and it has become particularly popular as a framing choice in residential builds.

Figure 1: Example of cold-formed steel in residential & light commercial projects (Reference)

Cold-Formed Steel as a Building Material

Cold-formed steel offers numerous benefits as a construction material.

Firstly, it is highly durable and resistant to corrosion, ensuring long-term structural integrity.

Secondly, cold-formed steel possesses higher strength, fire resistance, dimensional stability and is lighter than hot rolled steel and timber, allowing for the creation of lightweight structures permitting longer spans without compromising on load-bearing capabilities.

Comparison Between Cold-Formed Steel vs. Hot-Rolled Steel

The different manufacturing procedures between cold-formed steel and hot-rolled steel are summarised quite succinctly in this video as well as a high-level overview of the key differences between the two steel types in the below comparison.

Cold-Formed Steel

• Manufacturing Process: Cold-Working
• Mechanical Properties: High Strength
• Corrosion Resistance: Excellent
• Dimensional Stability: High
• Fire Resistance: High
• Design Flexibility: High
• Weight: Lighter
• Sustainability: Recyclable
• Price: More Expensive
• US Design Standards: American Iron and Steel Institute (AISI) S100 - "North American Specification for the Design of Cold-Formed Steel Structural Members."
• Australian Design Standards: AS/NZS 4600 - Cold-formed steel structures.

Hot-Rolled Steel

• Manufacturing Process: Hot-Working
• Mechanical Properties: High Ductility
• Corrosion Resistance: Moderate
• Dimensional Stability: Moderate
• Fire Resistance: Moderate
• Design Flexibility: Moderate
• Weight: Heavier
• Sustainability: Recyclable
• Price: Less Expensive
• US Design Standards: American Institute of Steel Construction (AISC) 360 - Specification for Structural Steel Buildings.
• Australian Design Standards: AS 4100:2020 - Steel structures

Cold-Formed Steel Framing

One of the primary applications of cold-formed steel in construction is framing.

Steel vs. Timber Framing

Cold-formed steel framing offers several advantages over traditional wood framing. It provides enhanced structural stability, as the material's consistent properties and uniformity eliminate common issues such as warping, splitting, or shrinking.

Moreover, cold-formed steel framing allows for greater design flexibility, facilitating the creation of complex architectural shapes and configurations that aren’t achievable with timber due to its rigid material properties.

While supply lead times and cost are the most critical factors in determining the choice of framing (which can be considered by contacting local framing suppliers), the below section can help a structural engineer choose between timber and steel framing.

Timber Framing

Advantages of Timber Framing

1. Sustainability: Timber is a renewable resource and has a lower carbon footprint compared to steel.
2. Insulation: Timber has natural insulating properties, providing better thermal performance and reducing energy consumption.
3. Aesthetics: Timber framing provides a warm and traditional look that many homeowners find appealing.
4. Cost-effectiveness: Timber framing is often less expensive than steel framing, especially for smaller residential projects which can be stick-built on site.
5. Ease of construction: Timber frames are lightweight and easier to handle, making them more suitable for DIY projects or remote locations.

Disadvantages of Timber Framing

1. Vulnerability to pests: Wood can be susceptible to termite and rot damage if not properly treated and maintained.
2. Limited span capabilities: Timber frames may require additional supports or columns for larger open spaces compared to steel frames.
3. Fire risk: Wood is combustible, which increases the risk of fire and may require additional fireproofing measures.
4. Shrinkage and warping: Wood can expand, shrink, and warp over time, potentially leading to structural issues or cosmetic problems.
5. Limited load-bearing capacity: Timber has lower load-bearing capacity compared to steel, restricting design options for larger or more complex structures.

Steel Framing

Advantages of Steel Framing

1. Strength and durability: Steel framing offers superior strength, stability, and resistance to weather, pests, and rot.
2. Design flexibility: Steel allows for longer spans and greater design freedom, making it suitable for modern architectural styles and large open spaces.
3. Fire resistance: Steel is non-combustible and offers better fire resistance, providing added safety and potentially lowering insurance costs.
4. Minimal maintenance: Steel frames are not susceptible to pests, rot, or warping, resulting in lower maintenance requirements.
5. Sustainability (recyclability): Steel is highly recyclable and can be reused, reducing environmental impact and waste.

Disadvantages of Steel Framing

1. Higher cost: Steel framing is generally more expensive than timber framing, particularly for smaller residential projects or projects with more non-standard dimensions.
2. Conductivity: Steel is a conductor of heat and electricity, which can affect energy efficiency and require additional insulation measures.
3. Aesthetics: Steel frames may lack the warmth and natural appearance of timber, which may not appeal to some homeowners.
4. Sound transmission: Steel can transmit sound more effectively than wood, potentially requiring additional soundproofing measures.
5. Weight and handling: Steel frames are heavier and require specialized equipment for assembly and transport.

From an environment perspective, steel framing is preferred in certain environments due to its inherent properties and advantages. These include:

• Seismic Zones: Steel framing has excellent ductility and resilience, making it ideal for areas prone to earthquakes. It can absorb and dissipate seismic forces, reducing the risk of structural damage.
• Extreme Weather Conditions: Steel framing is resistant to high winds, hurricanes, and other severe weather conditions. It offers enhanced durability and stability in regions with harsh climates.
• Industrial and Commercial Structures: Steel framing is widely used in industrial and commercial construction due to its versatility, ability to span long distances without intermediate supports, and suitability for large open spaces.

Timber framing, on the other hand, is preferred in different environments due to its unique characteristics and benefits. These include:

• Residential Construction: Timber framing is commonly used in residential buildings, particularly single-family homes and low-rise structures. It provides a warm and natural aesthetic appeal to these spaces.
• Environmental Considerations: Timber framing is a renewable and sustainable building material. It has a lower carbon footprint compared to steel, as trees absorb carbon dioxide during their growth. Timber is preferable in jurisdictions that have carbon taxes or financial incentives for using renewable materials.
• Rural and Remote Areas: Timber framing is often preferred in rural and remote locations due to its availability and ease of transportation. It can be sourced locally, reducing logistical challenges and costs.

Key Considerations for Structural Engineers

Structural stability and load-bearing capabilities of cold-formed steel are critical factors to consider.

Cold-formed steel framing products have undergone extensive testing to determine their structural properties and performance. Structural engineers should consult manufacturer specifications and relevant design standards to ensure proper design and selection of cold-formed steel components.

The typical failure modes for cold formed steel framing include:

• Buckling: Cold-formed steel members are slender and susceptible to buckling under compressive loads. Engineers need to carefully analyze and design the framing system to prevent buckling failures, especially in columns and walls subjected to axial compression.
• Lateral-Torsional Buckling: Cold-formed steel beams and joists can experience lateral-torsional buckling, which occurs when the member twists and deflects laterally under combined bending and torsion. Engineers must evaluate the member's resistance to lateral-torsional buckling and employ appropriate bracing or design provisions to prevent failure.
• Connection Failure: Adequate connection design is crucial for the structural performance of cold-formed steel framing. Insufficiently designed or poorly executed connections can lead to local failures, compromising the overall stability and load transfer within the framing system.
• Shear and Web Crippling: Cold-formed steel members, such as studs and joists, can fail in shear or experience web crippling. Shear failures occur when the applied load exceeds the shear capacity of the member. Web crippling occurs when the flanges of a member buckle or deform due to concentrated loads from bearing elements or fasteners.
• Material Yielding and Plastic Deformation: Cold-formed steel can undergo yielding and plastic deformation under high loads. Engineers must carefully analyze and design members to ensure they remain within acceptable stress limits to avoid excessive deformation or failure.
• Corrosion: While cold-formed steel is more resistant to corrosion compared to hot-rolled steel, it is still susceptible to corrosion when exposed to moisture or corrosive environments. Corrosion can weaken the steel members and compromise their structural integrity.
• Construction Tolerances: Cold-formed steel framing requires precise fabrication and installation to maintain the intended design and structural performance. Deviations from design tolerances during manufacturing or construction can affect the overall stability and strength of the framing system.

The use of appropriate design software is crucial for the accurate analysis and design of cold-formed steel members. Specialized software packages, such as ClearCalcs Calculations, are compliant with the AISI (American Iron and Steel Institute) or AS/NZS (Australian and New Zealand Standards) design codes, and provide efficient tools for engineers to optimize their designs.

Before using design software, it is essential to familiarize oneself with the relevant building codes and regulations in the United States and Australia.

Cold-formed steel design standards, such as AISI S100 in the United States and AS/NZS 4600 in Australia, provide guidelines for the safe and efficient use of cold-formed steel in construction.

ClearCalcs has these standards built into the cold formed steel design software and can design a range of cold-formed steel structural components, including:

• Cold-Formed Steel Beam (AS 4600:2018) - Joists, Rafters, Bearers, etc. to Australian Standards
• Cold-Formed Steel Column (AS 4600:2018) - Studs or Isolated Compression Members to Australian Standards
• Cold-Formed Steel Design-Only Member (AS 4600:2018) - Design Using External FEA Results to Australian Standards
• Cold-Formed Steel Beam (AISI S100-16) - Joists, Rafters, Girders, etc to US Standards
• Cold-Formed Steel Column (AISI S100-16) - Studs or Isolated Compression Members to US Standards

Cold-Formed Steel Manufacturers

For structural engineers considering the use of cold-formed steel, it is essential to work with reputable manufacturers who produce high-quality products.

In the United States, some well-known cold-formed steel manufacturers include BlueScope, Simpson Strong-Tie, and Clark Dietrich. These manufacturers adhere to stringent quality control measures and often have certifications, such as ISO 9001, which ensure their commitment to delivering reliable and consistent products.

The below section summarises the main cold-formed steel manufacturers in Australia & the US.

BlueScope Steel

Location: US & Australia

Certifications: BlueScope Steel holds certifications such as ISO 9001 for quality management systems, ISO 14001 for environmental management systems, and AS/NZS 4801 for occupational health and safety management systems.

Quality Control Measures: BlueScope Steel maintains strict quality control measures throughout their manufacturing process, including material testing, adherence to Australian standards, and regular inspections to ensure high product quality and performance.

Lysaght

Location: Australia

Certifications: Lysaght is certified with ISO 9001 for quality management systems and AS/NZS 4801 for occupational health and safety management systems.

Quality Control Measures: Lysaght upholds stringent quality control standards through comprehensive material testing, compliance with Australian standards, and continuous improvement initiatives. They also work with a network of authorized fabricators who undergo training and audits to ensure product quality.

ClarkDietrich Building Systems

Location: US

Certifications: ClarkDietrich holds certifications such as ISO 9001 for quality management systems, ISO 14001 for environmental management systems, and OSHA's SHARP (Safety and Health Achievement Recognition Program) certification.

Quality Control Measures: ClarkDietrich implements comprehensive quality control measures, including rigorous material testing, in-process inspections, and compliance with industry standards like ASTM. They have a robust quality management system in place to monitor and maintain consistent product quality.

Simpson Strong-Tie

Location: US

Certifications: Simpson Strong-Tie is certified with ISO 9001 for quality management systems and ISO 14001 for environmental management systems.

Quality Control Measures: Simpson Strong-Tie follows stringent quality control measures throughout their manufacturing process. This includes rigorous material testing, adherence to industry standards, and continuous product monitoring to ensure high-quality cold-formed steel components.

Steel Dynamics, Inc

Location: US

Certifications: Steel Dynamics, Inc. maintains certifications such as ISO 9001 for quality management systems and ISO 14001 for environmental management systems.

Quality Control Measures: Steel Dynamics implements rigorous quality control measures at every stage of their manufacturing process. This includes material testing, quality inspections, and compliance with relevant ASTM standards to guarantee product performance and reliability.

In Australia, although cold-formed steel is not standardized, structural engineers can refer to local manufacturers who specialize in cold-formed steel products.

Collaborating with experienced manufacturers is vital to ensure access to reliable technical support, accurate product information, and compliance with local regulations. It's important to note that certifications and quality control measures may evolve over time, and it's advisable to visit the manufacturers' websites or contact them directly for the most up-to-date information regarding their certifications and quality control processes.

Conclusion

Cold-formed steel is an increasingly popular choice for structural engineers in residential and light commercial projects. Its unique properties, including durability, strength, and resistance to fire and pests, make it an attractive alternative to traditional construction materials. Cold-formed steel framing offers advantages over wood framing, such as increased structural stability and design flexibility.

When using cold-formed steel, structural engineers must consider key factors such as design software, building codes, and manufacturer specifications. Utilizing specialized design software ensures accurate analysis and optimization of cold-formed steel members. Compliance with building codes, such as AISI S100 in the United States and AS/NZS 4600 in Australia, ensures the safety and quality of the project.

Choosing reputable cold-formed steel manufacturers is crucial for obtaining high-quality products. In the United States, manufacturers such as BlueScope, Simpson Strong-Tie, and Clark Dietrich are known for their commitment to quality and adherence to industry standards. In Australia, working with local manufacturers who specialize in cold-formed steel products ensures access to reliable technical support and compliance with local regulations.

In comparison to timber, cold-formed steel offers numerous benefits as a construction material. Its durability, strength, and resistance to fire and pests make it an ideal choice for residential and light commercial projects. By embracing this innovative material which can be easily designed for using ClearCalcs Calculations, engineers can achieve efficient and sustainable structures that meet the demands of the modern construction industry.

Structural engineers are encouraged to explore the possibilities of cold-formed steel for their next project. By embracing this innovative material, they can benefit from its superior properties, design flexibility, and sustainable attributes of CFS. As the construction industry continues to evolve, cold-formed steel offers a promising solution in the search for lightweight higher strength, corrosion & fire-resistant materials.