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Structural metal columns: What kind is safe?
- The problem with telescoping metal support columns.
The telescoping metal columns you sometimes see in basements are not approved for permanent structural use. Unfortunately, many do-it-your-selfers and sometimes contractors, use this type of column instead of an approved type. Fortunately, there is now a greater distinction being made between the different types of columns by lumberyards and manufacturers.
- What is the potential concern?
Telescoping adjustable metal support columns are not approved for use as permanent structural support by the IRC (International Residential Code). They are to be used as temporary support only. They have also been found to be subject to sudden and catastrophic collapse.
- Why are they not approved for permanent use?
No telescopic adjustable column has been evaluated by a U.S. evaluation firm and none of their manufacturers cite an engineering report to prove these columns' ability to carry a specific load. Also, according to the IRC, a steel column must be at least 3 inches in diameter. All telescopic columns are less than 3 inches in diameter. Think of these telescopic columns the way you would think of a car jack. They only exist to temporarily "jack up" a part of a building and should be replaced with a permanent column when the jacking up is done.
- What type column should I use?
There are three common types of steel support columns used in residential basements:
- Single-piece non-adjustable. Can be hollow or concrete-filled. (sometimes referred to as a “lally column“).
- Single-piece adjustable. a single hollow steel tube with an adjusting screw at its end that allows the height of the column to be adjusted on site.
- Telescoping two-piece columns. two or more hollow steel tubes with a smaller diameter tube fitting into a larger diameter tube with the sections held in place with steel supporting pins which pass through pre-drilled holes of both tubes. This also has one large screw on one end that allows the height of the column to be adjusted on site.
- Single piece columns are suitable for permanent structural use
Single piece columns are suitable for permanent use if labeled as such with a reference to an ICC-ES Report, a BOCA Report or a CCMC Evaluation. This means that it has been independently evaluated and found fit for permanent structural use. If it's manufactured for use in the U.S. it will cite an ICC-ES Legacy Report (issued by the International Code Council Evaluation Service), or a BOCA (Building Officials and Code Administrators) Report. They must be at least 3 inches in diameter.
- Telescoping metal support columns are not for permanent structural use.
Telescoping adjustable metal support columns are not approved for use as permanent structural support by the IRC (International Residential Code). They are to be used as temporary support only. They have also been found to be subject to sudden and catastrophic collapse.
- Requirements for permanent steel support columns:
Permanent one-piece (non-telescoping) adjustable columns should either be evaluated by a structural engineer or be labeled with reference to an ICC-ES or BOCA Report and thus independently evaluated as fit. It is recommended that columns be installed as follows:
- Must have permanent column restraint. The bottom plate must be permanently connected to a concrete footing with embedded anchor bolts or by complete encasement of bottom base plate in concrete.
- Column must be supported by a foundation capable of supporting the imposed loads.
- Top plate must be secured to the supported load and sized to the full width of the supported beam, or a 2” x8” wood cap be installed across the full width of the beam with the grain at 90° to the beam direction.
- Top plate must not be dished or bent. This is a defect
- Adjustable screw must not extend further than four inches. It can be installed with screw up or down. If installed downwards, then the screw is hidden and imbedded in concrete.
- Height adjusting screw must be disabled after installation.
- Must be installed vertically and plumb.
- Must have a lack of severe exfoliating rust that has compromised (crumbling or thinned steel) the column.
