Have you been told you need an RSJ but don’t understand what that means? That’s completely normal. RSJ stands for Rolled Steel Joist, and it’s one of the most commonly used structural elements in UK homes and commercial buildings. This guide breaks down what an RSJ is and why it matters.
What is an RSJ Used For?
An RSJ is a steel beam with a recognisable I-shaped cross-section, designed to carry heavy loads across an open span. In domestic settings, RSJ steel beams are most commonly used when a wall is being removed to create an open-plan kitchen or living space. When you remove a wall, something still needs to carry the weight of the floors and roof above, which is exactly what the beam does. RSJs also appear in loft conversions and larger structural alterations.
How Do RSJ Beams Work Structurally?
As soon as you understand what an RSJ is, you will recognise that the engineering behind it is pretty straightforward. The I-shape places most of the material at the top and bottom flanges, which is exactly where a beam experiences the greatest stress under bending. This makes RSJs incredibly efficient at resting bending forces while using comparatively little steel.
If you would like more information on sections like these, read our beginner’s guide to structural steel terminology, which covers the wider family of steel profiles that RSJs belong to.
Do You Need an Engineer to Size an RSJ?
Yes, you absolutely need an engineer to size an RSJ. You can’t just guess the right beam that you need; there is a calculation for it. A structural engineer will assess the span, load coming from above, supporting walls and column before choosing the beam’s size and steel grade.
If this is incorrect, you could experience sagging floors, cracked plaster or even worse. This is exactly why RSJ beams should never replace a proper structural design. Our structural steelwork design team takes care of this calculation process for every project Gorton Structures takes on.
What Does RSJ Installation Involve?
To install an RSJ, it tends to start with temporary propping to support the structure whilst the old wall is removed. The RSJ steel beam is then placed in position, bedded onto padstones or steel plates and permanently secured. After the beam is secured in place, the props can then be removed.
This is a job that must be completed by experienced steel installers; it is not a weekend DIY task. This is due to the loads involved and the risk to the building if it is installed incorrectly.
Where Else Are RSJs Used Besides Home Extensions?
RSJs and similar rolled actions are the backbone of larger structures too, such as mezzanine floors and wider steel-framed buildings. The same principles of load-bearing apply whether you’re opening up a kitchen or fitting out an industrial unit.
Ready to Get Your RSJ Specified Correctly?
Now that you understand what an RSJ is and how they apply to your own project, the next step is to get the right beam specified and installed. At Gorton Structures, we design, supply and install builders’ beams for homeowners and builders across the UK. Get in touch today to discuss your RSJ requirements.
