How Do I Fix Steel Beams to Padstones?

Fixing a steel beam to its padstone is a detail that is sometimes overlooked on site — builders assume the beam’s self-weight holds it in place. It does not. Beams must be positively fixed to their bearings for two reasons: to prevent accidental dislodgement during construction, and to provide the lateral restraint that the structural design relies on.

The Standard Fixing Method

The PorthouseDean specification for fixing steel beams to padstones is:

2 No. M12 chemically bonded anchors drilled and resin-fixed into the masonry or padstone, positioned centrally along the centreline of the supporting masonry wall.

In addition, the padstone itself must be strapped down to the adjacent masonry using 2 No. mild steel restraint straps.

Why Centreline Positioning Is Critical

The anchors must be installed along the centreline of the masonry, not to one side. When a beam is fixed off-centre relative to the wall below, it creates an eccentric loading condition — the beam wants to tilt or rotate, which puts stress on the masonry that the design does not allow for.

Do not bolt away from the centreline of the masonry or padstone. This is explicitly required on PorthouseDean documents.

When the Centreline Is Not Accessible

On some projects — particularly where a beam sits deep within a cavity and the centreline runs through inaccessible space — it is not possible to drill anchors along the centreline. In this case, the specification changes: strap the beam itself to the adjacent masonry using mild steel restraint straps. This is the approved alternative when centreline fixing cannot be achieved.

Beams Installed in Pairs

Where two beams are installed side by side (e.g. paired beams carrying a heavy load), they should be bolted together through the centre of the webs using M12 bolts at 500 mm centres, with spacer tubes between the webs to maintain the correct separation.

What Happens if It Is Not Done?

An unrestrained beam can move during construction — particularly when the floor build-up is being completed and construction loads are applied. A beam that has shifted from its bearing can change the load distribution assumed in the calculations. If the beam is also providing lateral stability to the building, an unrestrained beam creates a safety risk during construction.

Fix the beams as specified. Your structural engineer’s design assumes the connections are made.

Need Connection Details for Your Project?

PorthouseDean includes full bearing and fixing specifications on all structural drawings. Get a quote to have your project designed.