← Ontario Building Code FAQ
OBC DIVISION B · PART 9 · SECTION 9.17 — COLUMNS

What are the requirements for steel and wood columns in a basement in Ontario?

Prescriptive steel pipe columns supporting beams in houses must be at least 73 mm (2 7/8 in.) outside diameter with about 4.76 mm wall thickness, fitted with steel bearing plates; site-built wood columns must be at least 140 x 140 mm (6 x 6 in. nominal) and not smaller than the member they support.

Code reference
Columns in Part 9 buildings may follow prescriptive rules: steel pipe columns of minimum tabulated diameter and wall thickness with top and bottom plates to distribute loads, wood columns of minimum 140 mm square section (or equal to the width of the supported member, whichever is greater), each protected against moisture where bearing on concrete, and adjustable steel columns conforming to the applicable CAN/CGSB standard.
OBC Division B, Subsections 9.17.3. to 9.17.5.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

The everyday application is the telepost line under a basement beam. Adjustable columns must be a certified product, not just any screw jack, and the light-duty adjustable posts sold for temporary shoring are a common red flag at inspection. Wood posts bearing on the slab need moisture separation such as a membrane or elevated base. Columns must be positively connected top and bottom so they cannot be knocked out of plumb, an issue when basements get finished and posts are boxed in or relocated without reassessing the beam span.

Plain language

Those posts holding up the beam in your basement are structural. Steel ones need to be a proper certified column of adequate diameter with plates top and bottom, wood ones need to be at least 6x6 and kept off damp concrete, and none of them can be removed or moved without checking the beam.

Related questions

What size footing does a basement column need in Ontario?

Get answers like this for any code question

BUILDAiD Assist searches the building code and answers in plain English with exact citations — in seconds.

Try BUILDAiD Beta

This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.