Buying structural hollow sections (SHS and RHS): sizes, wall thickness, weight, ordering

Structural hollow sections are a staple of small sheds, canopies, mezzanines, light trusses and lightly loaded columns. This guide covers what to check before buying them: the sizes and wall thicknesses in our catalog, how to read weight per metre and per length, what the grade and standard tell you, and what to specify on the order.

What hollow sections are and the two families

A structural hollow section is a closed steel section with a uniform wall and rounded corners. The two shapes are the square hollow section (SHS) and the rectangular hollow section (RHS). In the Ahan Asa catalog both are supplied to the dimensional standard EN 10219-2 in grade S235JRH.

EN 10219 covers cold-formed welded hollow sections. EN 10210 covers hot-finished sections. UK steel industry guidance note SN31 explains that hot-finished sections are formed at normalising temperature (about 900 °C) and pass through a furnace, giving tighter corners and uniform grain structure and hardness across the section, while in cold-formed sections these properties vary, particularly in the corners and weld zone. SN31 adds that the corners of cold-formed sections are heavily cold-worked, which is why EN 10219-2 calls for larger corner radii to avoid corner cracking.

Sizes and wall thicknesses in the catalog

Sizes are written in millimetres as side × side × wall thickness.

The full range is in the hollow sections category. Outer corner radii are listed too: twice the wall thickness for 2.5 to 6 mm walls, 20 mm and 25 mm for 8 mm and 10 mm walls, and 36 mm for the 12 mm square section. That matters when another part must sit flush on a face or a weld falls near a corner.

Weight per metre and per length

Nominal weights from the Ahan Asa catalog, useful for estimating tonnage before you buy:

The table shows a useful rule: sections with the same perimeter and wall thickness weigh the same per metre. SHS 100×100×4 and RHS 120×80×4 are both 11.73 kg/m, so the choice between them comes down to structural behaviour, not steel weight. For nominal versus weighbridge weight, see our rebar and beam weight tables.

Square or rectangular?

A square section is equally stiff about both axes, which suits light columns, posts and members loaded from more than one direction. A rectangular section is stiffer about its major axis; installed with the long side in the direction of load, it is the more efficient choice for purlins, joists and other bending members. Orientation comes from the drawings, and turning a rectangular section the wrong way reduces its capacity. For main building columns, see our comparison of box columns and double-IPE columns.

Grade S235JRH and a caution on substitution

Tata Steel Nederland's data for S235JRH hollow sections to EN 10219 gives a minimum yield strength of 235 MPa for walls up to 16 mm, a tensile strength of 360 to 510 MPa and an impact energy of at least 27 J at +20 °C.

SN31 also makes three points worth knowing. Cold-formed sections should not replace hot-finished ones without first considering the design and fabrication implications, and a size-for-size comparison is not straightforward. Whether welding is allowed close to the corners of a cold-formed section (within 5t of the bend) depends on the ratio of corner radius to thickness and on the maximum thickness, per EN 1993-1-8 Table 4.2. And a cold-formed section that is correctly specified, produced and certified is suitable for all forms of construction. If your drawings call for EN 10210 or a higher grade, check with the structural engineer before ordering.

Ordering checklist

• State full dimensions: both outside sides and the wall thickness.
• Give quantity in a clear unit (lengths, metres or kilograms) and cross-check tonnage with the weight table.
• Confirm grade and standard on the quotation against the drawings.
• Ask for a test certificate on the actual product rather than a generic test report, as SN31 recommends.
• Measure wall thickness with a caliper on several lengths at delivery.
• Store sections on bearers clear of the ground so water does not sit inside; see storing steel on site.

Summary

Take three things from the drawings: shape and outside dimensions, wall thickness and grade. Estimate tonnage from nominal weight, and remember that equal perimeter and thickness means equal weight. Ahan Asa's hollow sections are cold-formed to EN 10219-2 in S235JRH, in 6 m lengths; any change of size, grade or manufacturing route needs the structural engineer's approval. To request a quotation for your project's sizes, contact us.