Yes, an I-beam can be used as a column, and in steel-framed buildings it very often is. The catch is that the best I-shape for a column is not the same as the best one for a beam. Columns use wide-flange W-sections whose flanges are about as wide as the section is deep (often called H-sections), because they resist buckling in both directions. A typical deep, narrow floor beam stood on end makes a weak column, and any I-shape used as a column has to be designed as one.
This post explains why the shape matters, what a good I-shaped column looks like, when a square tube is the better choice, and what to know before using a beam as a post in a house.
Beam vs column: different jobs
A beam spans horizontally between supports. Load along its length makes it bend, so a good beam section puts most of its steel in the flanges, far from the centre, in the direction it bends. That's why floor beams are deep and relatively narrow.
A column stands vertically and carries load down in compression. Short, stocky columns can carry close to the full strength of the steel. Taller ones fail first by buckling: bowing sideways under load. A column buckles in whichever direction it's weakest, so a good column section is stiff in every direction, not just one.
Many members do some of both. A column with a beam connected to one side carries some bending, and a beam in a braced frame may carry axial load. The engineer checks the combination under CSA S16. But the basic difference holds: beams want depth, columns want even stiffness.
Why a typical beam makes a poor column
An I-shape has a strong axis (bending the normal way, web vertical) and a weak axis (bending sideways). For a beam on its supports, the weak axis matters mainly for twisting. For a column, the weak axis usually controls the whole capacity.
The property that measures resistance to buckling is the radius of gyration (r). Divide the column's unbraced length by r to get its slenderness; the higher the slenderness, the lower the load it can carry. Here are two W-sections of the same depth, with values from the CISC section tables (rounded):
| Section | Shape | Depth x flange width (mm) | Mass (kg/m) | Weak-axis r (mm) | Slenderness at 3.0 m unbraced |
|---|---|---|---|---|---|
| W200x27 | Narrow beam section | 207 x 133 | 26.6 | 31.2 | about 96 |
| W200x46 | Square "H" column section | 203 x 203 | 46.2 | 51.2 | about 59 |
The W200x46 weighs more, but its weak-axis slenderness is far lower, so it carries much more as a column at the same height. The W200x27 is a perfectly good beam; as a 3 m column it would be governed by buckling about its narrow side.
The older S-shape (the traditional American Standard I-beam with tapered flanges) is worse again. The S200x27 has a weak-axis r of about 21 mm, so it is rarely a sensible column choice. Our post on I-beam vs W-beam vs H-beam compares those shapes side by side.
What a good I-shaped column looks like
Wide-flange column sections share a few traits:
- Flanges about as wide as the depth. Each depth group in the CISC tables includes heavier sections with wide flanges. These "H" proportions give a weak-axis r much closer to the strong-axis value.
- Thicker flanges and web. Columns carry concentrated loads at connections, and thicker plates help with local effects where beams frame in.
- Bracing about the weak axis. In many buildings, girts, walls or floor framing brace a column about its weak axis at intermediate points. The unbraced length about each axis can then differ, and the engineer checks both.
In multi-storey steel buildings the heavy W250, W310 and W360 column families are the workhorses. In houses and small commercial work, columns are usually smaller W-sections or HSS.
There are good reasons to use a W-shape column even when a tube could carry the load:
- Connections. Beams bolt easily to a W-column's flange or web with clip angles or shear tabs, and every face is reachable for bolting and welding.
- Splices. Column splices in multi-storey frames are simple to detail and bolt.
- Inspection and finishing. Open shapes are easy to inspect, paint, galvanize and fireproof.
Our post on beam-to-column connections shows the common details.
I-beam column vs square tube
For smaller columns, a square HSS is often the better choice. At about the same weight as a W200x27, an HSS 152x152x6.4 has a smallest r of about 59 mm, nearly twice the W-section's weak-axis value, so it is much less slender at the same height. It's also equally strong in both directions and has flat faces for base and cap plates.
| W-shape (I-shaped) column | Square HSS column | |
|---|---|---|
| Buckling resistance | Strong axis much stiffer than weak axis | Equal in both directions |
| Beam connections | Simple: flanges and web open for bolts and clips | Needs plates welded on or through-plate details |
| Typical use | Building frames, heavier loads, multi-storey | Posts in houses, canopies, light frames |
| Finishing | Open shape, easy to coat | Closed shape, ends sealed or vented for galvanizing |
The full comparison, with section properties, is in our post on W-beam vs HSS for beams and columns.
Using an I-beam as a post in a house
In Ontario houses built under Part 9 of the Building Code, the basic steel column is a pipe column with a minimum 73 mm outside diameter and 4.76 mm wall, and the code allows other sections where their capacity is shown to be adequate. That's how W-section and HSS posts end up on house drawings: a designer calculates the load and checks the section. Our guide on how to size a steel column for a house walks through that process.
Practical points for an I-shaped post in a house:
- It needs a footing. A column sits on a footing sized for its load, not on the basement slab.
- End plates and fastening. The post needs a base plate fastened to the footing and a cap plate fastened to the beam above. A post wedged in with shims isn't the column the designer checked.
- Orientation matters. If the post is braced in one direction (for example, by a wall), the designer may orient the weak axis toward that bracing.
- Finishing around it. The open flanges are harder to box in neatly than a round or square post. Our post on basement column wraps and covers covers the options.
Reusing a spare beam as a column
A leftover piece of beam can look like a free post. Before using one, a designer needs to know the section, confirm it works as a column for the load and height, and be comfortable with its grade and condition. Mill marks or test certificates rarely travel with offcuts, and old steel can be a different grade from new. Our post on reusing steel beams and offcuts covers what to check.
Columns cut, plated and delivered
Whether your drawings call for W-section columns, HSS posts or both, send them through our quote form. We fabricate columns with base plates, cap plates and connection clips welded on to CWB certified procedures, prepare shop drawings in-house, prime or galvanize to suit, and supply and install structural steel across the GTA and Ontario. See our steel products for the range.
Frequently asked questions
Can you use an I-beam as a post?
Yes, if it is the right section and it is designed as a column. Wide-flange W-sections with flanges about as wide as they are deep are standard column shapes. A deep, narrow beam section stood on end is usually a poor column because it buckles easily about its weak axis.
What is the difference between a steel beam and a steel column?
A beam spans horizontally and resists bending from loads along its length. A column stands vertically and carries load in compression down to the foundation. Both can be W-shapes, but columns favour sections that resist buckling in every direction.
Is an I-beam or a square tube better for a column?
At the same weight, a square HSS usually makes the better small column because it resists buckling equally in both directions. W-shape columns are easier to connect to beams and are common in larger buildings. The engineer picks based on load, height, bracing and connections.
Can I use a leftover steel beam as a basement post?
Not without a designer's check. The section has to be shown adequate as a column for the load and height, the grade of a leftover piece may be unknown, and the post needs proper end plates, a footing and a fastened connection to the beam.
