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April 21, 2011

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Work at height – Passive resistance

Safety Guidance Number 4 (SG4) has become the established minimum standard for fall prevention in the scaffolding industry. Following the release of the latest version of the guidance, Simon Hughes discusses the impact it has had on safety.

Work at height – There is little doubt that SG4 has had a significant effect in reducing falls from height in the scaffolding industry over the last 10 years. According to the National Access and Scaffolding Confederation’s own statistics, in 1999 there were 98 falls but just 20 in 2009. Despite an 18.3-per-cent increase in the number of operatives working within the NASC membership in the same period, this represents a 78-per-cent reduction in actual accidents and an 84-per-cent reduction in the accident frequency rate.

Although it was introduced in the mid-1990s SG4 really came into its own following the major revision in 2000 (SG4:00), as it represented a significant change and challenge to the established methods of working that had been practised in the scaffolding industry for decades.

SG4:00 introduced a new methodology called the ‘tunnelling principle’, whereby the scaffolder’s priority on any working platform was to create a safe working platform progressively, with guardrail protection and correctly supported working platforms – in the same way a miner shores up a tunnel as it is excavated – thus minimising the time exposed to risk. It also introduced the expectation on scaffolders to wear personal fall protection equipment (safety harnesses) at all times, as standard.

The next revision, in 2005, brought the guidance in line with the Work at Height Regulations (WAHR), and it was agreed with the HSE that it would henceforth be reviewed at least every five years, unless there were any changes in legislation, technology, or accident learning in the intervening years.

SG4:05 introduced, among other things, new collective protection methods that addressed the unprotected traversing element of the tunnelling principle, and new anchor devices that enabled scaffolders to attach their harnesses to higher points above the working platform, thereby reducing fall distances.

An interim guide (SG4 Appendix A) was published in 2008 to promote the use of collective protection further, and to signal the HSE’s intention to remove altogether the unprotected traversing element of the previous SG4 basic system of work in the scheduled 2010 revision.

Step change in scaffolding safety
The latest version was launched last November, with a foreword by the HSE’s head of construction, Philip White, who said: “This revision represents a step change in the way scaffold contractors erect their scaffold structures. The guidance is straightforward and comprehensive, and represents best practice within the industry.”
SG4:10 – ‘Preventing Falls in Scaffolding’1 places more emphasis on creating a ‘Safe Zone’ while erecting altering and dismantling scaffolding structures. As a minimum, the ‘Safe Zone’ requires a fully-boarded working platform and a single guardrail at 950mm when exposed to a risk of a fall. Additional precautions specified when working in the ‘Safe Zone’ include ‘clipping on’ if reaching below the guardrail, encroaching within 1m of an opening, leading edge, or other risk of a fall. It covers a wider variety of methods that employers can choose from for creating the ‘Safe Zone’, emphasising collective protection (guardrails) over personal protection (harnesses).

These advanced collective protection measures enable scaffolders to erect guardrail protection in advance of accessing the next lift, and to maintain guardrail protection while altering and dismantling scaffolding. The new guide separates these measures into three categories:
i Advanced guardrail systems – see figures 1 and 2;
ii Advanced guardrail tools – see figures 3 and 4;
iii Advanced guardrail methods – see figures 5 and 6.
Of course, in scaffolding, there is an inherent risk of a fall that cannot be completely eliminated in all operations, and there are still many instances where collective protection is not practicable and scaffolders will be required to use personal fall protection equipment when traversing, or working from the structure itself. Therefore, the NASC still recommends that scaffolders wear and use harnesses in accordance with the SG4 guidance and training and instruction received.

Deep impact?
The changes in the revised guidance should only significantly affect those who have not yet embraced the collective fall protection systems of work promoted by the earlier SG4:05 and Appendix A. The removal of the unprotected traversing element of the tunnelling principle should not have a major impact, as, according to the NASC’s own analysis, this represented only a small percentage of the scaffolder’s working day.

Nevertheless, the fact that it has hitherto been accepted by the HSE as a reasonably practicable solution in the absence of other alternatives means the initial investment in new equipment will be a major factor to consider for scaffolding contractors. However, by adhering to the guidance they and their employers can be sure that they are working safer and complying with the law. 

1 The new guide costs £25 for non-NASC members and can be ordered on its website at

Simon Hughes was a technical author on SG4:10

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