The safe-load numbers previously shown here had no sufficiently documented design basis and have been removed. A table should only be used when its conditions match the actual beam and building.
Audit a table in five steps
Identify the product. Match the complete section designation and steel grade. Approximate outside dimensions alone may not distinguish a historic joist from a modern UB.
Read the load definition. Check whether the number means total force, uniform force per metre or an area load over a specified width. Look for whether self-weight is included and whether the value is a service or factored load.
Check restraint and support assumptions. A drawing must show how the beam is supported and restrained. A table for one support condition does not cover a different arrangement simply because the span matches.
Identify the limiting condition. A deflection-limited figure is not automatically a strength, buckling, shear or bearing check. The lowest applicable resistance or serviceability limit may govern.
Keep the source and revision. Record the publication, page, date and complete notes with the design documentation. Do not rely on an unattributed image from a search result.
An example of a misleading comparison
A table headed “4 m span, 10 kN/m” describes a line load. Multiplying by 4 m gives 40 kN total force only if the load is uniform across that span. It does not mean a 40 kN force may be placed at any point, and does not show that the supporting masonry can carry the reactions.
Use manufacturer data to identify section properties. Use the SCI/BCSA Blue Book with its design basis and a competent designer for resistance information. Our calculator methodology explicitly lists the checks our tools omit.
Structural work requires a chartered structural engineer and the applicable Building Control approval. This educational article has not received an independent engineering review.