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The entry point to large-span domestic steelwork, for openings of 7 metres and beyond.

356 x 171 x 45 dimensions and weight

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

What is a 356 x 171 x 45 used for?

The 356 x 171 x 45 is the beginning of the large-span end of domestic and light commercial steelwork. Published tables place it around 7 metres under domestic loading, and at that scale the design almost always warrants close engineering attention – this is not a section anyone should be selecting from a table. It is specified for very wide open-plan conversions, large rear extensions on detached properties, and openings where an entire structural wall is being removed across the full width of a substantial house. At 352mm deep it will usually be visible below the ceiling line unless the floor structure is reformed around it, which is a design decision worth making early since it affects both cost and the finished appearance. It is also frequently the point at which fire protection and, if left exposed, corrosion protection and finish become part of the specification rather than an afterthought.

Indicative span

Under typical UK domestic loading, published load tables place the 356 x 171 x 45 in the region of 6.5m to 7.5m. 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 356 x 171 x 45 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 356 x 171 x 45 weighs approximately 270kg. 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: 356x171x45, 356 x 171 x 45 UB, UB 356x171x45, 356×171 UB45. 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.