Beam Suspended from Another Beam — How the Connection Works

When a secondary beam needs to connect to a primary beam but cannot sit on top or frame in at the same level, it can be suspended from the bottom flange of the primary. This creates a downstand — the secondary beam hangs lower than the primary — but enables intersecting beams to work at different levels.

Why This Connection Is Used

The suspended connection is particularly useful in loft conversions, where beams at different levels allow the floor void depth to be minimised. If the secondary beam sat on top of the primary, the total combined depth of both sections would be greater than if the secondary hangs from the underside. Suspending the secondary helps maximise floor-to-ceiling height.

It is also used where access constraints on site make framing into the web of the primary beam impractical.

What the Connection Consists Of

The secondary beam’s end is fitted with a plate that connects to a bracket welded to the underside of the primary beam’s bottom flange. Grade 8.8 black bolts complete the joint. The connection transfers shear force (vertical load) from the secondary into the primary; it also provides a tying and restraining effect between the two members.

Standard specification:
– Welds: 6 mm full profile fillet weld
– Bolts: Grade 8.8 black
– Plates: S275 mild steel
– All grades per PorthouseDean calculations

The Downstand Implication

Because the secondary beam hangs below the primary, there will be a visible depth difference at the connection point — typically expressed as a step or bulkhead in the ceiling. If a flat, uninterrupted ceiling is important for the design, this connection type is not compatible with that goal. In that case, a side-of-beam flexible end plate connection at the same soffit level is the alternative.

Before Fabrication

The fabricator must produce workshop drawings and submit them to PorthouseDean for approval before manufacturing. The bracket geometry and weld details must match the structural design. Do not fabricate based on judgement or generic details.

Questions About Your Loft Steelwork?

Contact PorthouseDean to discuss beam arrangements for your loft conversion or structural alteration.