TG20 and SG4: what these scaffolding standards actually mean

Anyone reading a few scaffolding company websites will run into references to TG20 and SG4 fairly quickly, usually presented as evidence of a company's professionalism. They're genuinely useful things to understand, since they're the core technical guidance behind how a safe scaffold is actually designed, built and worked on in the UK — not just marketing terms.

TG20 is NASC's technical guidance for tube-and-fitting scaffolding — the traditional style of scaffold built from individual tubes and couplers rather than a pre-engineered system scaffold. It provides operational, design and user guidance covering good practice for how a scaffold of a given configuration should actually be constructed to be structurally sound. In practice, this means that for any tube-and-fitting scaffold, there should exist either a TG20 compliance sheet — a standard reference document confirming the specific configuration falls within recognised safe limits — or a bespoke design drawing produced for that specific job where the configuration falls outside standard parameters. This matters because a scaffold that looks fine to a layperson isn't the same thing as a scaffold that's actually been designed or checked against recognised structural guidance for its height, loading and configuration.

SG4 is a separate piece of guidance, titled "Preventing Falls in Scaffolding Operations", and it covers something different from TG20 — rather than the finished structure, SG4 addresses the actual process of erecting, altering and dismantling a scaffold, which is itself one of the more hazardous parts of any scaffolding job, since workers are inherently at height without a completed platform to stand on for parts of the process. SG4 sets out specific protocols for preventing falls during that erection and dismantling process, covering both traditional tube-and-fitting scaffolds and more modern pre-engineered system scaffolds. This is worth knowing because a scaffold's ultimate safety once complete is only part of the picture — how safely it was actually put up and taken down, by workers who were themselves at risk during that process, is a separate and equally important question.

Both TG20 and SG4 are published and maintained by NASC, the National Access & Scaffolding Confederation, the UK scaffolding industry's trade body. It's worth being clear that neither is itself an Act of Parliament or a direct statutory requirement in the way something like the Work at Height Regulations 2005 is — they're industry technical guidance, developed by people with deep expertise in scaffolding, that represents the recognised standard for how compliant, safe work should actually be done. Following recognised guidance like TG20 and SG4 is generally how a scaffolding contractor demonstrates it's meeting the underlying safety duties that do exist in law, rather than being a separate legal obligation in its own right.

For a customer commissioning scaffold work, the practical value of knowing about TG20 and SG4 is that it gives you something concrete to ask about. A reputable scaffolding company should be able to show a TG20 compliance sheet or a specific design for a non-standard configuration for your particular scaffold, and should be able to describe, if asked, how their crew follows SG4 fall-prevention procedures while actually building and later dismantling it — not just point to the finished structure as evidence everything was done properly. A company that's unfamiliar with these terms, or dismissive when asked about them, is a reasonable signal to look elsewhere, since these aren't obscure or unusual things for an established scaffolding contractor to know well.

NASC membership itself is also worth checking, since it's a further signal that a company operates to these recognised industry standards as a matter of course rather than only when directly asked. None of this replaces asking a company directly about its own specific practices and being satisfied with the answers, but knowing what TG20 and SG4 actually cover means those questions can be asked with some confidence about what a good answer should sound like.

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