Yes, HSS (hollow structural section) can be used as a beam, and rectangular HSS often is: for short spans, exposed beams, canopy and balcony edges, and any member that has to resist twisting. For a typical floor beam carrying joists, though, a W-shape (wide-flange "I-beam") usually gives more bending strength for the same weight, and it is far easier to connect to. The choice comes down to how the beam is loaded, braced and connected, and it is made by the designer.
This article covers when an HSS beam makes sense, which sizes get used, and the limits that come with a closed tube.
What an HSS beam is
HSS is steel tube in square, rectangular and round shapes, made in Canada to CSA G40.21 (commonly Grade 350W, Class C or Class H). It's a structural section like a W-shape or a channel, designed under CSA S16. For the basics, see what is HSS steel.
When people say "HSS beam" they almost always mean a rectangular tube set on edge: the deeper side vertical, so it bends about its strong axis. A square tube works as a beam too, but for the same weight a rectangular tube on edge is stiffer in the direction gravity loads act. Round HSS is rarely used as a beam except in exposed architectural framing.
Canadian HSS names are metric versions of imperial sizes. HSS 203x102x6.4 is an 8 x 4 x 1/4 in tube: 203 mm deep, 102 mm wide, with a 6.4 mm wall.
Common HSS sizes used as beams
Rectangular tubes in the 152 mm to 305 mm depth range cover most light beam work in houses, decks, canopies and small commercial frames. Masses are per metre and match our HSS size chart.
| Section (mm) | Imperial (in) | Mass (kg/m) |
|---|---|---|
| HSS 152x76x6.4 | 6 x 3 x 1/4 | 20.7 |
| HSS 152x102x6.4 | 6 x 4 x 1/4 | 23.2 |
| HSS 203x102x6.4 | 8 x 4 x 1/4 | 28.3 |
| HSS 203x152x6.4 | 8 x 6 x 1/4 | 33.4 |
| HSS 203x152x9.5 | 8 x 6 x 3/8 | 48.5 |
| HSS 254x152x9.5 | 10 x 6 x 3/8 | 56.1 |
| HSS 305x203x9.5 | 12 x 8 x 3/8 | 71.4 |
The table is a list of sections, not a load table. Two tubes of the same outside size can differ a lot in strength because of wall thickness, and the right one depends on span, load and bracing. The final section always comes from the engineer.
Where an HSS beam is the better choice
A W-shape has most of its steel in the flanges, far from the centre, which makes it very efficient at bending in one direction. But it is an open section, which makes it weak in twisting and prone to rolling sideways when unbraced. A closed tube behaves differently, and that difference is what makes HSS useful as a beam:
- Unbraced beams. An open W-shape without lateral support can fail by twisting sideways (lateral-torsional buckling) before reaching its full bending strength. A closed tube is largely free of that problem, so it can carry its load over a span with little or no bracing along its length.
- Off-centre and twisting loads. Balcony edge beams, canopy beams carrying outriggers, beams with brackets on one side and spandrel beams all carry torsion. Closed tubes are hundreds of times stiffer in torsion than W-shapes of similar weight.
- Bending in two directions. A beam that takes gravity load one way and wind or impact the other way suits a section that is strong both ways.
- Exposed work. Flat faces, clean edges and no flange ledges to collect dirt make HSS a common pick for exposed beams, canopies and frames that will be painted.
- Small frames and short spans. Lintels in steel frames, short headers, equipment and mezzanine framing, and welded frames often use HSS because the posts are HSS too, and tube-to-tube connections weld cleanly.
- Decks and outdoor frames. Rectangular HSS is a common deck beam material on steel post frames.
The numbers behind these points, including a side-by-side comparison of a W200x27 against square and rectangular HSS of the same weight, are in W-beam vs HSS.
Limitations of HSS beams
Less efficient in plain bending
For a braced floor beam with joists bearing on top, the W-shape usually wins. At about the same weight, a W200x27 has roughly twice the strong-axis stiffness of an HSS 152x152x6.4 and more than an HSS 203x102x6.4. Using HSS where a W-shape would do often means more steel for the same span.
No code span tables
The steel beam span tables in Part 9 of the 2024 Ontario Building Code (Table 9.23.4.3 and Tables 9.23.4.3.-A to -J) list W-shapes only. There's no prescriptive table to pick an HSS house beam from, so an HSS beam in a house is an engineered member. For W-shape spans, see our guide to the Ontario steel beam span tables.
Harder connections
Connections are where tubes cost more. A W-shape has open flanges and a web you can bolt to from both sides. A tube is closed:
- You can't reach inside to put a nut on a bolt, so bolted connections need through-bolts (which can crush the tube walls unless detailed for it), special blind fasteners, or welded tabs and plates.
- Beam-to-column and beam-to-beam joints are usually shop-welded plates, tabs or end caps, which adds fabrication.
- Wood joists can't sit on a flange. They hang from hangers fastened to a wood ledger or nailer attached to the tube, or sit on top of it.
Thin walls under concentrated loads
Tube walls are thinner than the web of a comparable W-shape and are unsupported across the width of the tube. At bearing points and under concentrated loads (a post landing on the beam, a point load from above), the walls can crush or buckle locally. The engineer checks this and may call for a thicker wall, a cap or bearing plate, or stiffening at those points.
Depth limits
The deepest rectangular HSS sizes are still far shallower than the deepest W-shapes. For long spans or heavy loads, a W-shape, a built-up section or a truss is usually the realistic choice.
The inside of the tube
The inside of a closed tube can't be painted after it's sealed. Tubes are normally sealed with welded cap plates, or vented and drained where they will be hot-dip galvanized or exposed to moisture. The designer and fabricator agree on that detail before fabrication. Our article on whether structural steel needs paint or galvanizing covers finishes.
HSS or W-shape: quick guide
| Situation | Usually better |
|---|---|
| Floor beam carrying joists, braced by the floor | W-shape |
| Long span or heavy load | W-shape, built-up section or truss |
| Beam with little or no lateral bracing | HSS often works well |
| Edge beam with load on one side | HSS |
| Exposed beam or canopy | HSS, by appearance |
| Short beam in a welded HSS frame | HSS |
| Beam in a house where Part 9 tables are used | W-shape (the tables list W-shapes only) |
Never swap one shape for another on a structural drawing without the engineer's written approval. A tube and a W-shape with similar "size" numbers are not interchangeable.
Getting HSS beams fabricated
We supply HSS and W-shape beams cut to length and fabricated to your shop drawings, with cap plates, connection plates, tabs and holes as detailed, along with the HSS posts they sit on. Welding is done in our CWB certified shop, and shop drawings are prepared in-house. If your project needs engineering, ask us about it when you request a quote.
Send your drawings for a quote, or browse our steel products for beams, posts and plates.
Frequently asked questions
Can HSS be used as a beam?
Yes. HSS is a structural section designed under CSA S16 like any other, and rectangular HSS is often used for beams, especially short spans, exposed beams and members that have to resist twisting. Weight for weight, though, a W-shape is usually the more efficient beam for a floor.
What does HSS steel beam mean?
HSS stands for hollow structural section, a closed steel tube that is square, rectangular or round. An HSS beam is simply a tube used to carry load in bending, typically a rectangular tube set with its deeper side vertical.
Is an HSS beam stronger than an I-beam?
Not in ordinary bending at the same weight. A W-shape puts more of its steel in the flanges, so it is stiffer about its strong axis. HSS wins when the beam is unbraced, carries loads off-centre or bends in two directions, because a closed tube resists twisting far better.
Are there span tables for HSS beams in Ontario?
Not in the building code. The Part 9 steel beam span tables in the 2024 Ontario Building Code list W-shapes only, so an HSS beam has to be designed, usually by an engineer working to CSA S16.
