The size of the RSJ (Rolled Steel Joist) beam you need for a 4-meter span depends on various factors such as the load it will bear, design, locality, types of structure, building codes and regulation, and structural requirements.

Commonly the term RSJ used by builders and the people who work with steel. RSJ is actually a long beam made from hot or cold-rolled steel. This is also known as a Universal Beam (i-Beam), hot rolled Steel section such as H beam (universal column), I beam (universal beam), angles, channels and etc.

Typically RSJ are used in construction project such as field of agriculture construction, industrial construction, multi storey building, different factories and residential projects. Today is the demand of steel structure in the field of construction projects that replace the depending on reinforced cement concrete, their higher strength, less time consuming, make it ideal for residential project in short duration.

The universal RSJ steel beam sizes represented by their height of the web in mm x width of the flange in mm x the weight per metre in kilograms. When you measure the height and width it look like as capital I, hence also being known as I beam. The thickness of the web and flange can varies.

**What size RSJ do i need for 4m?** To determine the appropriate size of a Rolled Steel Joist (RSJ) you can use thumb rule. A ‘rule of thumb’ for RSJ beam size says 1/24th X span, therefore 1/24th X 4m = 166mm, so assume a 178×102×19 or thereabouts for 4 meters span.

## What size rsj beam do i need for 4m span

According to thumb rule, rolled steel section depth are in the range of 1/2 inches of depth for each foot of span (L/24). Or depth of the RSJ beam as roof joist = 0.5 × span, where length expressed in meters and depth members in mm.

As per RSJ span rule of thumb, the depth of the RSJ beam is about 1/24th of span in mm and their width is 1/3 to 1/4 of the depth. If beam span is 4m in length, then their depth = (4 × 1000) ÷ 24 = approx 166mm and width is 166/2 = approx 81mm. So, you would need something like 178×102×19 size of RSJ beam for a 4-meter span.

Typically the RSJ beam size required for 4m span need to be 178×102×19. This includes the 178mm is depth of the web of RSJ beam, 102mm is the width of the flange and 19 is the weight in kg per metre.

**Conclusions:-**

The size of the RSJ (Rolled Steel Joist) beam you need to span a 4-meter have to be 178×102×19, where 178mm is depth of web of RSJ beam, 102mm is flange width and 19 is the weight in kilograms per meter.