TG20:21 Explained: What Scaffolders Need to Know

TG20:21 is the NASC technical guidance for tube-and-fitting scaffolding, and it is the current version: TG20:13 was withdrawn on 12 October 2021. In plain terms, it is the reference that tells you whether a common scaffold can be built to a standard compliant configuration, or whether the job needs a bespoke structural design. If you scaffold in the UK, it is the document sitting behind a lot of what you do, even when you never open it.

This is what it is, and why it matters on site.

What TG20:21 covers

TG20:21 applies specifically to tube-and-fitting scaffolds, the traditional method covered in our guide to scaffolding types. It is made up of a few parts:

• The eGuide, software that generates a compliance sheet for a given scaffold configuration.
• The Operational Guide, the practical rules for erecting and using scaffolds.
• The Design Guide, the engineering basis behind it.
• The User Guide, which explains how to use the lot.

For TG20:21 these are accessed through the NASC ePortal on a subscription, so the guidance is kept current online rather than in a fixed printed book.

Compliant configuration vs bespoke design

This distinction decides how a scaffold gets signed off.

If the scaffold you need matches a configuration the eGuide covers, you can produce a TG20 compliance sheet for it. That sheet shows the scaffold is compliant with recognised guidance without needing an individual structural design. It is quicker, cheaper and covers a huge share of everyday scaffolds: standard independents, towers, loading bays and the like.

If the scaffold falls outside those configurations, because of unusual height, loading, sheeting, ground conditions or shape, it needs a bespoke design from a scaffold designer. TG20 is not a shortcut around that. It is the tool that tells you which side of the line your scaffold sits on.

TG20:21 widened the range of configurations the eGuide can handle, adding things like exterior birdcages, tube-and-fitting mobile towers, loading bays without beams and tied independent scaffolds with three inside boards. More configurations covered means fewer jobs needing a full bespoke design.

Is it the law?

No. TG20:21 is industry guidance, not legislation. But it is the accepted way of demonstrating that a common tube-and-fitting scaffold is safe and built to a recognised standard, which is why main contractors and clients expect to see it. It supports, rather than replaces, your legal duties, which sit under the Work at Height Regulations 2005 and wider health and safety law.

What it means for you

You do not need to be a designer to work within TG20. What helps is knowing the distinction: a standard scaffold to a compliance sheet, an unusual one to a bespoke design, and never guessing which is which. That judgement is part of what separates a Part 2 or Advanced scaffolder from a labourer, and it is the kind of understanding that comes with your CISRS training.

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