Compliance · 12 min read

TG20:21 Compliance Guide for UK Scaffolders

TG20:21 is the NASC's user guide and design guide for tube-and-fitting scaffolds. This is the plain-English version, what it actually asks for on site, how tie patterns and load classes work, and the checks that keep an inspector happy.

What TG20:21 is (and isn't)

TG20:21 is the current edition of the NASC's Good Practice Guidance for Tube and Fitting Scaffolding. It replaces TG20:13 and is the reference the HSE, principal contractors, and scaffold inspectors expect you to work to. It has three parts you'll actually touch:

• The User Guide, the everyday rulebook: dimensions, tie patterns, bracing, board configurations.
• The Design Guide, the technical basis; you go here (or your designer does) when a scaffold falls outside the "compliant" envelope.
• The eGuide, the software that generates a TG20:21 compliance sheet for a standard configuration. If your job matches a compliant scaffold, the sheet is your evidence.

TG20:21 is not a legal document by itself, but working to it is the practical way UK scaffolders demonstrate compliance with the Work at Height Regulations 2005 and CDM 2015.

Load classes at a glance

Every working platform has a load class. Pick the wrong one and the scaffold is either overloaded or over-specified (and priced out of the job). The classes you'll meet on UK sites:

Rule of thumb: bricklayers = Class 4, general trades = Class 3, painters = Class 2. If more than one platform will be loaded at once, TG20:21 restricts how many can be at each class, check the eGuide output, not memory.

Tie patterns explained

Ties are what stop the scaffold walking away from the building. TG20:21 uses three tie patterns and every compliant scaffold is built to one of them:

• Pattern A, one tie every other lift, alternate bays. The lightest pattern; only allowed on lower load classes and shorter scaffolds.
• Pattern B, one tie every lift, alternate bays. The workhorse pattern for most general-access scaffolds.
• Pattern C, one tie every lift, every bay. Used on sheeted / netted scaffolds and heavy-load configurations where wind and imposed loads are highest.

Sheeting or netting a scaffold changes the wind loading dramatically . You almost always jump to Pattern C, and often need a bespoke design. Don't sheet a Pattern B scaffold "just for the weekend" without re-checking it.

Each tie must resist the design tie force (typically 6.1 kN in tension for a compliant scaffold). Drilled-anchor ties should be proof-tested; through-ties and reveal ties should be inspected and recorded on the handover.

The site checks that matter

Most TG20:21 failures on site come down to the same handful of items. Run this list before signing off a handover:

1. Base plates and sole boards, every standard on a base plate, sole boards on anything softer than concrete, and the scaffold plumb before the first lift goes on.
2. Standards, ledgers, transoms, spacings match the compliance sheet. 2.0 m or 2.4 m bay lengths are the common ones; anything else is bespoke.
3. Ties, right pattern, right frequency, and none missed around openings. Log any tie you had to relocate.
4. Bracing, façade bracing every 6 bays, ledger bracing at alternate pairs of standards. Missing bracing is the #1 thing an inspector will flag.
5. Boards, guardrails, toeboards, fully boarded working lift, double guardrails, 150 mm toeboards. Brick guards if you're storing materials.
6. Load class signage, a scaffold tag at every access point stating the load class. If it isn't tagged, the site team will assume the wrong class.
7. Compliance sheet on file, the TG20:21 eGuide output (or a bespoke design) handed to the client with the handover certificate.

When you need a bespoke design

The eGuide covers a wide envelope, but you drop out of "compliant" territory the moment any of these are true:

• Scaffold is over 50 m in length or the covered heights.
• Sheeting or netting on a pattern the eGuide doesn't cover.
• Cantilevered lifts, bridges over 3 m, or truss-outs.
• Loading bays combined with heavy trades on the same run.
• Ground conditions that need a spread base or grillage.

In those cases the compliance sheet is not enough, you need a bespoke design from a scaffold designer working to the TG20:21 Design Guide and BS EN 12811. Price it in from day one; retrofitting a design after the scaffold is up is where jobs lose money.

Getting the paperwork right, fast

The compliance sheet, handover, and inspection records are what protect you if anything goes wrong. On a typical domestic or light commercial job you need:

• TG20:21 compliance sheet (or bespoke design pack).
• Handover certificate, signed by the scaffolder and the client.
• Weekly inspection records (Reg 12, Work at Height Regs).
• Insurance and CISRS card records on file.

Our guide to scaffold tags, handover certificates and inspection records covers exactly what each of those documents must contain and who signs them.

ScaffQuote generates a branded TG20:21 compliance sheet alongside every quote, so the paperwork is done before the tubes hit the van. If the configuration falls outside TG20 compliant scaffolds, we flag it and tell you a bespoke design is needed instead of quietly issuing a sheet that doesn't cover you.

TG20:21 is a trademark of the National Access & Scaffolding Confederation (NASC).