RSJ vs Steel Beam: What’s the Difference?

If you are planning a house renovation, removing a load bearing wall, or working on a construction project, you will likely encounter the terms RSJ and steel beam. These terms are often used interchangeably in the construction industry, but there are key differences. Understanding what each one means, and when to use them, can help ensure the structural integrity of your property and avoid additional costs.

This guide explains what RSJ stands for, explores the RSJ vs Steel Beam comparison, and outlines what to consider before installation.

What is an RSJ?

RSJ stands for Rolled Steel Joist. It is a type of steel beam that has an I-shaped or H-shaped cross section, and is commonly referred to as an RSJ beam or simply an RSJ. These beams are hot-rolled during manufacturing, giving them strength and durability. RSJ beams are designed to support heavy loads and are frequently used in residential and commercial construction projects throughout the UK.

RSJs are particularly effective when removing load bearing walls, supporting floors or ceilings, and creating open-plan layouts. Their cross section allows for efficient bending resistance in one direction, making them ideal for carrying structural weight vertically through a wall or column.

What is a Steel Beam?

A steel beam is a general term used to describe any beam made from structural steel. This includes RSJs as well as other types such as:

• Universal Beams (UBs)

• Universal Columns (UCs)

• I Beams

• H Beams

• T Beams

• Cold Rolled Steel Beams

• Box Beams

Steel beams are available in a wide range of standard sizes and shapes, each suited to different structural needs. Universal beams, for example, are often used in construction today due to their wide flanges and high load-bearing capacity. Universal columns, on the other hand, are more effective when supporting vertical elements.

RSJ vs Steel Beam: Key Differences

While RSJs are a type of steel beam, not all steel beams are RSJs. The main differences come down to the shape, function, and where they are used.

• Shape: RSJ beams have a standard I or H cross section with tapered edges. Other steel beams such as universal beams or columns have different proportions and flange widths.

• Use: RSJs are often used in domestic projects like removing a load bearing wall. Universal beams or columns may be used in larger structures such as commercial buildings, bridges, or industrial units.

• Manufacturing: RSJs are hot rolled. Other beams may be cold rolled depending on the application and required performance.

• Support and Load: RSJs are designed primarily for vertical support and bending resistance in one direction. Some beams, like box or universal columns, offer bidirectional bending resistance and better support for complex structures.

When to Use an RSJ

An RSJ is commonly used when you need to:

• Remove a load bearing wall

• Support an upper floor or ceiling

• Create an open-plan living space

• Reinforce an existing structure

• Support heavy loads over a long span

Because of their strength and cost-effectiveness, RSJs are a popular choice for home renovations. However, using the wrong type of beam or installing it incorrectly can cause structural problems. Always consult a structural engineer before starting work.

Steel Beam Calculations and the Role of a Structural Engineer

Before installing any steel beam, it is essential to perform accurate steel beam calculations. A structural engineer will assess the building’s layout, load requirements, and the existing structure to determine the correct size, length, and material for the beam.

Factors they will consider include:

• Structural weight and load distribution

• Beam shape (RSJ, I beam, H beam, etc.)

• Flange width and cross section dimensions

• Resistance to bending, buckling, and shear

• Welding and fixing requirements

• The material of the surrounding walls and floors

Professional steel beam calculations help prevent issues such as deflection, collapse, or poor alignment. An experienced builder will also work closely with the engineer to ensure everything is installed to specification.

Steel Beam Materials: Hot or Cold Rolled?

RSJs are typically hot rolled, meaning they are shaped at high temperatures to improve strength and flexibility. Cold rolled steel beams are shaped at room temperature, resulting in a more precise finish but less ductility.

For most domestic construction projects, hot rolled steel is preferred due to its strength and ability to support heavy loads. Cold rolled steel is more often used in smaller structures or where aesthetic appearance is important.

Common Types of Steel Beams in UK Construction

• RSJ (Rolled Steel Joist): I or H-shaped, strong, and widely used.

• Universal Beam (UB): Similar to RSJs but with wider flanges. Common in house building and commercial projects.

• Universal Column (UC): Designed to carry vertical loads. Square cross section provides excellent support.

• I Beam / H Beam: Names used to describe the cross section shape, often overlapping with RSJs.

• T Beams / Box Beams: Used for specific applications depending on span, shape, and support needs.

Each of these beams has a role in supporting walls, floors, roofs, or other structural elements in a property or building.

Why Steel is the Preferred Material for Beams

Steel is highly durable, recyclable, and can support more weight with less material compared to timber or concrete. It is resistant to warping, rot, and insect damage. These qualities make it the ideal material for supporting structures in both modern and traditional buildings.

Using steel beams in your construction project also allows for longer spans without the need

for additional vertical supports, creating open-plan spaces and reducing build times.

Final Thoughts

RSJs and other steel beams are essential components in construction today. While RSJs are a specific type of hot rolled steel beam with a tapered I-beam profile, the term “steel beam” covers a wide range of shapes and functions. The right choice depends on the load, span, and purpose within the structure.

Before beginning any work involving structural changes, speak to a qualified structural engineer who can perform steel beam calculations and recommend the most efficient beam for your project.

For further information about RSJ beams, universal beams, or structural steel installations, speak to our team today.