Corner Window Post Alignment: SHS Column Position vs the Glazing Line

On extensions and ground floor open plans with corner glazing, a steel column is often required at or near the corner to carry the beam or structure above. The structural ideal is to position the column centrally under the beam — for efficient load transfer with no eccentricity.

But the glazing line often wants to sit at or very close to the corner, which conflicts with where the structural post needs to be.

Why Post Position Matters

An SHS (square hollow section) column should ideally be centred under the RHS beam it supports. Eccentricity — where the column centre is offset from the beam — introduces bending into both the beam and the column. If the offset is small, it may be within tolerance. If the offset is large, the connection detail must account for the additional moment, and the column size or cap plate arrangement must be revised.

Options When the Glazing Line Clashes

1. Extend the Beam

If the beam can be extended so that its end sits behind the outer glazing line — while the column sits further inside the building — the post can be positioned away from the glazing without eccentricity. The beam end then cantilevers slightly over the column. This cantilevered length must be checked structurally and will typically require a Change Request.

2. Box Out the Column Internally

Accept that the column sits slightly inside the glazing line and box it out with a slim plasterboard or timber surround. In many contemporary interiors, a boxed column at the corner becomes an architectural feature. The structural connection remains concentric.

3. Move the SHS Into the Cavity Line

The column can be moved to align with the cavity inner face, with a cap plate or offset connection to the RHS beam. The eccentricity introduced must be checked — the beam end plate or cap plate must be designed for the resulting moment as well as the vertical load. This requires a formal Change Request.

4. Run Windows Outside the Steel

Design the glazing to sit outside the structural steel envelope — the post sits in the interior and the windows wrap around it externally. This separates the structural and glazing lines entirely.

5. Secondary Angle or Plate Fixing

In some arrangements, a secondary steel angle or plate is welded to the post to create an outer support face for the glazing, while the post maintains its structural position. This is typically an architectural metalwork detail, not a primary structural change, but the engineer should review it.

Get Confirmation Before Fixing the Design

If your architectural drawings show a corner window close to the required post location, raise this with PorthouseDean at the design stage. Moving a post after the structural package is issued requires a Change Request and potentially revised calculations. Resolving the conflict before first issue saves time and cost.

Contact us or raise a Change Request to discuss corner post alignment on your project.