Beam Sitting on Top of Another Beam — Connection Details

Where a secondary beam must bear on the top flange of a primary beam — rather than framing into its side — the connection is a direct top-of-flange bearing, typically with bolts to prevent uplift or lateral movement.

When This Connection Is Used

This type of connection is specified in two main scenarios:

1. Where different soffit levels are acceptable or desirable — for example, in a loft conversion where the supporting beam at eaves level sits lower and the secondary beam sits on top, allowing a shallower floor zone at the connection
2. Where the main beam happens to cross the location where the secondary beam needs to terminate, and framing into the web is not practical

If a downstand bulkhead is visible below the connection point, this connection type is the likely reason. The supporting beam is lower than the secondary beam, and the step is visible in the ceiling below.

On UB or UC Supporting Beams

The secondary beam sits on the top flange of the primary UB or UC. The connection uses bolts through the beam webs to prevent movement, with a cleat or plate detail as shown in the structural drawings. The primary beam must have adequate torsional resistance to carry the eccentric load from the secondary beam bearing on one side — this is confirmed in the engineer’s calculations.

On RHS or SHS Supporting Beams

For RHS (rectangular hollow section) or SHS (square hollow section) primary beams, the secondary beam sits on the top face. The hollow section’s torsional stiffness is significantly higher than an open UB section, making this arrangement more straightforward structurally. Fixing is again via bolts as shown on the drawings.

Fabrication Drawing Approval

As with all fabricated steel connections, the fabricator must submit workshop drawings to PorthouseDean for approval before manufacturing begins. Fees may apply for approval reviews outside the original project scope.

Questions?

If the connection arrangement on your project is unclear, contact PorthouseDean to discuss the specific beam references and positions.