What is an RSJ? Discover the Benefits of Using RSJs in Your Next Project

by | Feb 24, 2023 | Loft Conversion | 0 comments

The construction industry is an important sector of the economy, involved in building, renovating, and maintaining various types of structures, such as residential, commercial, and industrial buildings. The industry encompasses many professionals, from architects and engineers to contractors and labourers, who work together to create safe, functional, and aesthetically pleasing spaces.

One of the key elements in the construction industry is the use of structural steel, which provides a strong, durable, and flexible material for building structures. Within this category of steel, RSJ steel, or Rolled Steel Joists, are a popular choice for constructing beams, which are critical elements in the construction of floors, roofs, and walls.

The RSJ beam is made by rolling steel into the shape of an I-beam, with a wide flange at the top and bottom and a narrow web in the centre. This design provides the beam with great strength and stiffness while minimising its weight of the beam. RSJs can be used alone as a structural element or in combination with other materials, such as concrete or wood, to create composite structures.

You may have heard the term “RSJ” used before if you’re involved in construction projects. But what exactly is an RSJ, and what are its benefits in your next project? This article will explore the answers to these questions and more.

Understanding RSJs

RSJs, or “Rolled Steel Joists,” are steel beams commonly used in construction to support structures such as floors, roofs, and walls. They are often used in industrial and commercial buildings, as well as in residential construction.

RSJs are made by rolling steel into the shape of an “I” beam, with a wide flange at the top and bottom and a narrower web in the centre. This design provides excellent strength and stiffness while minimising the weight of the beam.

RSJs can be used as a standalone structural element or combined with other materials, such as concrete or wood, to create composite structures. They are often combined with other RSJs to create larger structural elements such as trusses or girders.

When selecting an RSJ for a particular application, several factors must be considered, including the span of the RSJ beam, the load it will be supporting, and the structural support available. The weight of the beam is also a consideration, as it will affect the size of the crane or other equipment needed to install it.

Reduced need for supporting columns, allowing for greater design flexibility

Rolled Steel Joists (RSJs) are a popular choice for construction projects due to their ability to support heavy loads and provide greater design flexibility. One of the critical benefits of RSJs is that they can reduce the need for supporting columns, which in turn allows for greater design flexibility.

Traditional building methods often require the use of multiple supporting columns to distribute the weight of the structure. However, by using RSJs, the need for these columns can be reduced or even eliminated in some cases. This can be achieved due to the increased load-bearing capacity of RSJs, allowing them to span greater distances without the need for additional support.

Reducing or eliminating supporting columns allows for greater design flexibility, as it frees up more space within the building. This can be particularly useful in industrial or commercial settings where large, open spaces are often required. By using RSJs, architects and designers can create more open, aesthetically pleasing, and functional spaces.

Furthermore, reducing the number of columns can also save on construction costs. This is because the need for additional materials and labour is decreased, resulting in a more efficient and cost-effective building process.

Cost savings in construction due to fewer materials and less labour required

One of the key benefits of using RSJs is that they can result in cost savings in construction due to the fewer materials and less labour required.

Compared to other types of beams, RSJs can be manufactured with fewer materials, which can help reduce steel beams’ overall cost. RSJs are produced by rolling steel sheets, which are then shaped into the desired size and shape. This process requires less steel compared to other methods of beam production, resulting in cost savings for the construction project.

In addition to material savings, RSJs can also reduce labour costs. The steel beam installation process for RSJs is relatively straightforward and can be completed more quickly than other beams. This can reduce the labour costs associated with the installation process, resulting in a more efficient and cost-effective construction project.

The ability of RSJs to span longer distances without additional supporting columns can also result in cost savings. Reducing the number of columns required decreases the need for additional materials and labour, resulting in a more cost-effective building process.

Durability and longevity, making RSJs a long-term investment

RSJs are made from high-quality steel resistant to wear and tear, corrosion, and fire. This makes them ideal for various construction projects, from residential to commercial and industrial structures. They can withstand heavy loads and are resistant to bending and deformation, ensuring that they can support the weight of the building and maintain their structural integrity over time.

In addition to their strength, RSJs are also long-lasting. They do not require regular maintenance and can maintain their strength and structural integrity for decades without needing to be replaced. This makes them a wise investment for any construction project, as they offer long-term durability and reliability.

Moreover, the use of RSJs can help to increase the lifespan of a building. The structural strength provided by RSJs means that the building can withstand natural disasters and extreme weather conditions, reducing the risk of damage and the need for repairs. This can save money long-term and ensure the building remains safe and stable for years.

Applications of RSJs

RSJs, such as roof structures and load-bearing walls, are commonly used in residential construction. They are also frequently used in commercial and industrial construction for supporting mezzanine floors, warehouse shelving, and heavy machinery.

In infrastructure projects, RSJs can be used to construct bridges, tunnels, and other structures requiring solid load-bearing capacity.

Here are some of the most common applications of RSJs:

Floor and roof structures

RSJs are commonly used to construct floor and roof structures. Due to their strength and load-bearing capacity, they can support heavy loads and span long distances without additional support.

Industrial and commercial buildings

RSJs are often used to construct industrial and commercial buildings such as warehouses, factories, and shopping centres. The strength and durability of RSJs make them ideal for supporting the weight of heavy machinery and equipment.


RSJs are also commonly used in the construction of bridges. Their ability to span long distances without additional support makes them ideal for bridge construction.

Mezzanine floors

RSJs are often used to construct mezzanine floors, which are intermediate floors built between the main floors of a building. The strength and load-bearing capacity of RSJs makes them ideal for supporting the weight of mezzanine floors.

Residential buildings

RSJs can also be used in the construction of residential buildings, particularly in the construction of large open-plan spaces such as living rooms, dining areas, and kitchens. RSJs can create a more spacious and open environment by reducing the need for supporting columns.

Factors To Consider When Using RSJs

When using RSJs in construction projects, it’s essential to consider several factors. These include structural requirements, building codes and regulations, environmental factors, and project budgets. Consulting with a structural engineer or another qualified professional can help ensure that RSJs are used safely and effectively in your project.

Load-bearing capacity

One of the primary considerations when using RSJs is their load-bearing capacity. It is important to ensure that the RSJ is strong enough to support the load it will be subjected to and adequately installed and supported.

Span length

The length of the span the RSJ will be supporting is another important consideration. Longer spans will require larger, stronger RSJs to support the load, while shorter spans may be able to be supported by smaller RSJs.

Placement and support

Proper placement and support of the RSJs are critical for ensuring the safety and stability of the building. RSJs should be placed, supported by the manufacturer’s guidelines, and securely fastened to prevent movement or shifting.

Fire resistance

While RSJs are made of steel, which is generally fire-resistant, it is vital to ensure that the RSJs used in a construction project meet the required fire safety standards.

Building codes and regulations

Construction projects must comply with local building codes and regulations. It is crucial to ensure that RSJs are permitted and meet all requirements.


other types of beams. It is essential to consider the RSJ cost in comparison to other options and to evaluate whether the long-term benefits of RSJs outweigh the initial investment.


RSJs are versatile and durable materials that can offer a range of benefits in construction projects. Their increased load-bearing capacity, reduced need for supporting columns, and flexibility in design make them an excellent choice for many applications.

Whether you’re building a residential, commercial, or industrial project, using RSJs can be a wise investment in the long term. So, consider these benefits when planning your next project and consult with a qualified professional to help ensure the safe and effective use of RSJs.

Emmanuel Nwaebo

Emmanuel Nwaebo is the Managing Director at Powerpillar Ltd and has more than 25 years experience in building construction and renovations. He has a bachelor’s in Electronics and Electrical Engineering with certification in Construction Health and Safety Technician (CHST). With an experience in managing construction and renovation services for years, he is extremely passionate about property management and loves helping people find their dream property.

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