A steel column is a vertical member that carries load down from beams and floors to the foundation, and in buildings it is almost always a wide flange (W) shape, a square or rectangular tube (HSS), or a round pipe. Which one gets used depends less on raw strength than on buckling: a column usually fails by bowing sideways long before the steel itself is crushed, so the shape’s stiffness about its weakest axis matters most.
This guide covers the three common column shapes, the numbers that decide between them, how columns connect at top and bottom, and where the adjustable posts in houses fit in. Every dimension below comes from the AISC Shapes Database v16.0, checked October 2026.
What a Steel Column Does
Beams collect floor and roof load and deliver it to their ends. Columns pick it up there and carry it straight down, storey by storey, adding load at each floor until it reaches a base plate and footing. Most of what a column carries is axial compression. Some columns also take bending, either because a beam frames in off-center or because the column is part of a moment frame that resists wind or seismic sideways load.
The terms overlap with beam vocabulary. A “post” is usually a short or light column, a “stanchion” is an older British word for the same thing, and a “lally column” is a specific residential product: a steel tube, sometimes filled with concrete, that sits under a basement beam. That product has its own guide on lally columns and adjustable basement posts.
Why Buckling Decides Column Size
Push down on a short, stubby piece of steel and it fails by yielding: the steel itself gives way. Push down on a long, thin one and it bows out sideways at a much lower load. That sideways failure is buckling, and almost every building column is long enough for it to govern.
Engineers track this with the slenderness ratio, KL/r: the effective length of the column (KL) divided by its radius of gyration (r). The radius of gyration is a section property that describes how far the material sits from the center, and a bigger r means a stiffer column against buckling. The AISC Specification (ANSI/AISC 360) recommends keeping KL/r for compression members at or below 200.
The key detail is that a shape has a different r about each axis. A column buckles about whichever axis is weakest, so the smaller value, usually ry, is the one to watch. That single fact explains most of the differences between the shapes below.
The Three Common Column Shapes
Wide flange (W) columns
The W shape is the workhorse column in commercial and industrial buildings. Beams bolt easily to its flanges and web, it comes in a huge range of weights, and the heavier “column” sections in each depth have flanges about as wide as the section is deep. That squarer outline raises ry, which is what a column needs.
Compare two shapes of similar weight. A W12x40 is 11.9 in deep with an 8.01 in flange and an ry of 1.94 in. A W10x49 is 10.0 in deep with a 10.0 in flange and an ry of 2.54 in. The W12x40 is the lighter and better beam, but the W10x49 is far stiffer against weak-axis buckling, which is why the squarer W8, W10, W12 and W14 sections are the usual column choices. The full list of depths and weights is in our wide flange beam sizes chart.
Square and rectangular HSS columns
Hollow structural sections (HSS) are cold-formed tubes. A square HSS has the same r about both axes, so it has no weak direction, and it looks clean when exposed. That makes it common for canopies, storefronts, mezzanines, light commercial buildings and residential steel posts. The usual specification is ASTM A500, which covers cold-formed welded and seamless carbon steel structural tubing in rounds and shapes for building and bridge construction (ASTM A500/A500M-23 scope, checked October 2026).
The trade-off is connections. Bolting a beam to a closed tube is harder than bolting to an open flange, so HSS columns often use welded shear tabs or through-plates. Sizes and wall thicknesses are listed in our HSS and square tube sizes chart.
Round pipe and round HSS columns
A round section is equally stiff in every direction, which suits columns well. Pipe columns are common in houses, warehouses and outdoor structures, and round HSS appear in architectural work where the look matters. Outside diameters and walls are in our round steel tube sizes chart.
Common Column Sections Compared
The table lists some frequently used column shapes with their weight, area and radius of gyration about each axis. All values are from the AISC Shapes Database v16.0, checked October 2026. For a W shape the smaller r is ry; for the tubes and pipes r is the same both ways.
| Shape | Weight (lb/ft) | Area (in²) | rx (in) | ry (in) |
|---|---|---|---|---|
| W8x31 | 31 | 9.13 | 3.47 | 2.02 |
| W10x33 | 33 | 9.71 | 4.19 | 1.94 |
| W10x49 | 49 | 14.4 | 4.35 | 2.54 |
| W12x40 | 40 | 11.7 | 5.13 | 1.94 |
| W12x65 | 65 | 19.1 | 5.28 | 3.02 |
| W14x90 | 90 | 26.5 | 6.14 | 3.70 |
| HSS4x4x1/4 | 12.21 | 3.37 | 1.52 | 1.52 |
| HSS6x6x1/4 | 19.02 | 5.24 | 2.34 | 2.34 |
| HSS6x6x3/8 | 27.48 | 7.58 | 2.28 | 2.28 |
| Pipe 3 STD | 7.58 | 2.07 | 1.17 | 1.17 |
| Pipe 4 STD | 10.8 | 2.96 | 1.51 | 1.51 |
Two things stand out. An HSS6x6x1/4 weighs 19.02 lb/ft yet has an r of 2.34 in, higher than the ry of a W10x33 or W12x40 that weigh roughly twice as much. That is why tubes are efficient as lightly loaded columns. And going from HSS6x6x1/4 to HSS6x6x3/8 adds area (strength) but slightly lowers r, because the extra wall goes on the inside. Heavier is not always stiffer against buckling.
These numbers show how the shapes compare. They do not tell you what load a column can carry. Capacity depends on the steel grade, the unbraced length, the end conditions and any bending, and a licensed structural engineer has to size and check every column.
Steel Grades for Columns
W-shape columns in US buildings are normally rolled to ASTM A992, which covers rolled structural shapes for building framing and bridges (ASTM A992/A992M-22 scope, checked October 2026). Square and rectangular HSS are usually ASTM A500, and pipe is commonly ASTM A53. The grade sets the yield strength used in the design, so the drawings always state it, and substituting a different grade needs the engineer’s approval.
Column Connections: Top and Bottom
At the base
A column ends in a base plate, welded on in the shop, that bolts to the foundation through anchor rods set in the concrete. For steel erection in the US, federal rules say all columns shall be anchored by a minimum of 4 anchor rods, and each anchorage, including the column-to-base-plate weld and the foundation, must resist a 300 lb eccentric gravity load applied 18 in from the column face (OSHA 1926.755, Column anchorage, checked October 2026). The rods themselves are covered in our guide to anchor bolts.
At the top and at each floor
Beams connect to columns with simple shear connections (clip angles or shear tabs) in most framing, or with moment connections where the joint has to resist rotation. Multi-storey columns are spliced, usually a few feet above a floor where the splice is easy to reach, and a column may step down to a lighter section higher in the building where it carries less load. The difference between the two connection types is explained in moment connection vs shear connection.
Steel Columns in Houses
In homes, steel columns usually appear under a basement or garage beam. Three kinds show up:
- Adjustable steel posts. A screw jack at the top, sold for temporary shoring or as rated permanent columns. Only products specifically rated for permanent use belong in a finished structure.
- Fixed pipe or lally columns. A cut-to-length steel tube with plates at each end, sometimes concrete-filled.
- Square HSS posts. Common when a steel beam replaces a load-bearing wall; the post is usually sized and detailed by the engineer who designs the beam.
Whatever the type, the column needs a proper footing under it, a positive connection at top and bottom so it cannot kick out, and a size that a licensed structural engineer or the building department has accepted for that load.
How Engineers Choose a Column Shape
- Load and height. Heavy loads over long unbraced heights favor heavier, squarer W sections; light loads favor HSS or pipe.
- Connections. Lots of beams framing in from different directions favor the open W shape, which is easy to bolt to.
- Appearance. Exposed columns in retail, residential and architectural work are often HSS or round sections.
- Fire protection. Columns in many buildings need fire protection, and the shape affects how much spray coating or paint is needed.
- Fit. Columns hidden in walls have to fit the wall depth, which can rule out wide flanges.
Steel Column FAQ
What is the most common steel column shape?
In commercial buildings, the wide flange (W) shape, typically a W8, W10, W12 or W14 with flanges about as wide as the section is deep. In light structures and houses, square HSS tubes and round pipe are more common.
Is an H-beam or an I-beam better as a column?
For the same weight, the wider-flanged H-shaped section is usually better, because its wider flanges raise the weak-axis radius of gyration and resist buckling. Deep, narrow I-shaped sections are more efficient as beams.
How much weight can a steel column hold?
There is no single number. Capacity depends on the shape, the steel grade, the unbraced height, how the ends are held and any bending from off-center loads. A licensed structural engineer has to calculate it for the actual column.
Why does a column fail by buckling and not crushing?
Most building columns are long relative to their cross-section. A long, slender member becomes unstable and bows sideways at a load well below the one that would crush the steel. That is why the radius of gyration and the unbraced length matter so much.
Do steel columns need to be bolted to the footing?
Yes. A column needs a positive connection to its foundation so it cannot slide or tip. For structural steel erection, OSHA 1926.755 requires at least four anchor rods per column; residential posts use the fastening the engineer or product listing specifies.
Reference information only, not engineering advice. Disclaimer.