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The standard section for full-width rear openings and bi-fold doors on larger properties.

305 x 165 x 40 dimensions and weight

Approximate total weight by length — this is what determines how the beam is offloaded on site.

What is a 305 x 165 x 40 used for?

The 305 x 165 x 40 is where domestic steelwork starts to become properly structural. Published load tables place it in the 5.5 to 6.5 metre range under domestic loading, which covers the full rear width of most detached and larger semi-detached houses. It is the section most often specified for large open-plan conversions, full-width bi-fold and sliding door openings, and larger loft conversions in detached properties. The combination of 304mm depth and a 165mm flange gives it both capacity and good lateral stability, though at this span the deflection limit rather than bending strength is frequently what governs the design. Practically, a 6 metre length weighs around 240kg. That puts it firmly into HIAB offload territory and, on a restricted urban site, is worth discussing before the order is placed rather than when the lorry arrives.

Indicative span

Under typical UK domestic loading, published load tables place the 305 x 165 x 40 in the region of 5.5m to 6.5m. That assumes a simply supported beam with an evenly distributed load, an imposed load of around 1.5 kN/m² and a dead load of 0.5–0.8 kN/m².

Grades, lengths and finishes

The 305 x 165 x 40 is normally supplied to BS EN 10025-2 in S275JR or S355JR. S355 is the higher strength grade and is increasingly the default across the supply network; if your calculations specify one grade, tell us, because the two are not interchangeable. Mill certificates can be supplied with the order on request.

Beams are supplied cut to your lengths rather than as standard mill lengths, and we can arrange:

• Cutting to size — supplied ready to install, no cutting on site
• Drilling, notching and holes to your engineer’s details
• Welded cleats, end plates and connections
• Painting and priming, including intumescent coatings
• Galvanising for external or exposed applications

Delivery

A 6m length of 305 x 165 x 40 weighs approximately 240kg. At that weight the beam needs mechanical offload at the kerb and, in most cases, mechanical assistance to get it into position. We deliver direct to site across London, the South and the Midlands, with HIAB lorry crane offload available on request. If access is restricted — a terraced street, a rear garden, limited headroom — tell us at quote stage rather than on the day, and we’ll plan the delivery around it.

Other sizes in the range

Also searched as: 305x165x40, 305 x 165 x 40 UB, UB 305x165x40, 305×165 UB40. The term “RSJ” is still widely used for universal beams, though strictly it refers to the older rolled steel joist section with tapered flanges.

• All universal beam sizes
• Universal columns (UC) — where the load is vertical rather than spanning
• RSJ beams
• PFC parallel flange channels

Common questions

Dimensional data shown is nominal and for guidance. Span figures are indicative and must not be used in place of structural calculations.