Hop-up bracket tie bars: Tie bars are incorporated into two and three board hop-up brackets to hinder bracket rotation (i.e., splaying) and to avert the displacement and falling of planks.

Beyond simply preventing plank falls, it is crucial that the tie bar is meticulously designed and installed to mitigate the risk of its own unintentional dislodgement and subsequent falling.

Photograph 1 illustrates an instance of a tie bar on a two-board hop-up bracket. This guidance centers on addressing the inadvertent dislodgement concern associated with tie bars and establishes fundamental standards.

There have been a number of incidents in Queensland where tie bars have become inadvertently detached and workers have either fallen or been struck by a falling tie bar.

Any single inadvertent force should not be able to dislodge any part of the tie bar. For example, a bouncing motion caused by an object falling down on the scaffolding deck or an inadvertent vertical or horizontal force should not be able to dislodge the tie bar.

The locating pins on tie bars are generally of two types:

• Straight pins
• Pins with a 45 degree bend half way along the pin.

Pins with the 45 degree bend are usually more effective at helping to prevent inadvertent dislodgement of the pin, particularly when the pin is inserted so that the end of the pin points back towards the scaffolding (refer Photographs 2 and 3).

The issue of inadvertent dislodgement of tie bars is not specifically discussed in the Queensland Scaffolding code of practice 2021 (PDF, 1.63 MB) (the code).

Placement of Tie Bars: To ensure the secure positioning of tie bars, each tie bar should be installed in a manner that prevents the dislodgement of any individual pin through a single distinct action, without a scaffolding plank resting on top of the bar. When the scaffolding manufacturer provides explicit documented instructions for tie bar installation, those instructions must be strictly adhered to. In cases where such instructions are absent, the following examples illustrate both preferred and unsafe practices. While not exhaustive, these examples reflect principles that can be applied in various scenarios.

Additionally, besides mitigating the risk of falling scaffolding components, the design of the hop-up bracket and tie bar should aim to minimize the gap between planks. According to Section 5.7 of the code, concerning working platforms, no single gap between planks should exceed 25 mm, and the overall gap between all planks should not surpass 50 mm.

Example (a) - Preferred Tie bar pins with a 45-degree bend, positioned with the end of the pin directed back towards the scaffolding. 

It is acceptable for the scaffolding plank to be either on top of the horizontal part of the tie bar (see Photograph 2) or adjacent to the tie bar (see Photograph 3). When positioned next to the tie bar, the tie bar can face either inwards or outwards (see Photograph 4). In all instances, the tie bar should not dislodge with a single action. Rotating the tie bar backward should result in contact with the plank.

Example (b) – Preferred

Tie bar with straight pins.

The scaffolding plank is positioned on top of the horizontal part of the tie bar with the plank pushed up against vertical face of the tie bar (refer Photograph 5). In this example, the tie bar is unlikely to become dislodged as both the tie bar and the plank would have to be pushed up vertically at the same time.

Photograph 5: Tie bar with straight pins and plank sitting on tie bar – preferred.

Example (c) – Unsafe

Tie bar with straight pins.

Scaffolding plank is positioned next to but not on top of the tie bar (refer Photographs 6 and 7). In this example, the tie bar can become dislodged if the bar moves vertically and the plank does not resist movement.

Example (d) – Unsafe

Tie bar pins with 45 degree bend with end of pin pointing away from scaffolding (refer Photograph 8). In this example, the tie bar can become dislodged if it is rotated forwards. There is no plank to resist this movement.

Photograph 8: Pin pointing away from scaffolding with plank next to tie bar – unsafe.