TG20 Compliance Guide: Using the eSP Tool to Generate Compliance Sheets for Tube and Fitting Scaffolds

Summary

TG20:21 (Technical Guidance document 20, 2021 edition) is the definitive UK reference document for tube and fitting scaffolding. Published by the NASC, it provides comprehensive guidance on the structural design and erection of tube and fitting scaffolds, replacing previous editions TG20:08 and TG20:13.

The TG20 system works on the principle that scaffolds falling within its defined parameters are pre-engineered — you don't need site-specific structural calculations if the configuration matches what TG20 has already proven safe. The eSP tool is the practical mechanism for confirming this: enter the configuration parameters, and the tool generates a Compliance Sheet confirming TG20 applicability or flagging that a structural design is needed.

This matters to scaffolding contractors because it reduces the cost and time of scaffold design — no engineer needed for the majority of standard scaffolds. It matters to principal contractors because a TG20 Compliance Sheet is clear documentary evidence that the scaffold has been checked against an established standard. For NASC members, generating Compliance Sheets is expected practice.

Key Facts

• TG20:21 — current edition published 2021; replaces TG20:13 and TG20:08
• eSP tool — free online tool at nasc.org.uk; generates Compliance Sheets in minutes
• Compliance Sheet — document confirming the scaffold configuration is within TG20 design parameters
• Tube and fitting only — TG20 applies specifically to tube and fitting scaffolds, not system scaffolds
• Standard configurations — eSP covers independent tied, putlog, truss-out, buttressed, and birdcage scaffolds
• Scope limits — bay width, lift height, facade height, and tie pattern must all fall within TG20 limits
• Non-standard — anything outside eSP scope requires structural engineer design; do not proceed without it
• Scaffold register — TG20 compliance sheets should be retained in the scaffold register for the life of the scaffold
• Wind zone — UK is divided into wind zones (1, 2, 3); eSP accounts for wind when calculating tie requirements
• Ground conditions — TG20 assumes adequate ground bearing; poor ground may require separate assessment
• Timber boards — TG20 covers standard BS 2482 scaffold boards; non-standard decking may require separate assessment
• Tube specification — TG20 is based on Grade 43A (S275) steel tube to BS EN 39:2001
• Coupling specification — fittings to BS EN 74-1:2005 (swivel, right angle, putlog couplers)

Quick Reference Table: TG20 Standard Configuration Limits

Exact limits depend on duty class, wind zone, and specific configuration. Always run eSP for the specific parameters.

Detailed Guidance

How to Use the eSP Tool

The eSP tool is available free to all users (not just NASC members) at the NASC website. Steps:

1. Log in / register — free registration required; firms can register multiple users
2. Start new calculation — enter project reference, date, and contractor details
3. Select scaffold type — independent tied, putlog, birdcage, or other
4. Enter configuration parameters:
   • Facade height (m)
   • Bay width (m) — measured centre to centre of standards
   • Lift height (m) — bottom of boards to bottom of boards
   • Duty class (1–6 per BS EN 12811-1)
   • Number of board widths
   • Soil/ground conditions (assumed adequate by default)
   • Wind zone (eSP auto-populates from postcode)
   • Exposure category (sheltered, normal, exposed)
5. Review results — eSP calculates whether the configuration is within TG20 scope and specifies the required tie pattern
6. Generate Compliance Sheet — print or save PDF; the sheet shows all input parameters, the required tie pattern, and confirmation of TG20 scope

The Compliance Sheet references TG20:21 and is the documentary evidence that the scaffold has been designed to an accepted standard. It replaces an engineer's design certificate for standard configurations.

Understanding TG20 Tie Patterns

Ties are the critical element TG20 calculates — the Compliance Sheet will specify:

• Tie pattern — e.g., "every alternate bay, every lift" or "every third bay, every other lift"
• Tie type — reveal tie, box tie, or lip tie (each has different pull-out strength; TG20 specifies minimum)
• Tie loads — the calculated load in kilonewtons that each tie must resist

The tie pattern depends on facade height, bay width, lift height, duty class, and wind zone. A scaffold in a coastal or elevated location (Wind Zone 3) will require more ties than the same scaffold in a sheltered urban location (Wind Zone 1).

Common reasons eSP produces a "not in scope" result:

• Facade height exceeds 50m
• Bay width exceeds 2.4m (common for bricklayers requiring wider working space)
• Lift height exceeds 2.0m
• Non-standard decking or substrate
• Truss-out or cantilevered configuration

Non-Standard Scaffolds Requiring Structural Design

When eSP returns "not in scope", a structural design is required from a qualified structural engineer with scaffolding design experience. This is not optional — erecting a scaffold outside TG20 scope without a design is a serious compliance breach.

Common non-standard scenarios:

• Bay widths >2.4m (required by bricklayers or for special access)
• Facade height >50m
• Truss-out scaffolds (cantilevered off the building)
• Scaffolding over roads or railways (additional loading and consents required)
• Heavily loaded scaffolds (duty class 5 or 6)
• Scaffolds on poor ground (soft fill, made ground, basements below)
• Complex geometry (curved facades, re-entrant corners, multi-level offsets)

For non-standard designs, retain the engineer's calculations and design certificate in the scaffold register alongside the TG20 Compliance Sheet (if parts of the scaffold are standard).

Scaffold Duty Classes Explained

The duty class entered into eSP determines the design loading and therefore the required number of standards, board widths, and tie density. Classes per BS EN 12811-1:

The agreed duty class must be recorded on the scaffold handover certificate. Clients and principal contractors must not load the scaffold above the agreed class without notifying the scaffolding contractor and potentially revising the design.

Wind Zones and Exposure Categories

TG20 uses UK wind zones based on the geographic location of the site:

• Zone 1 — most of England (lower wind speeds)
• Zone 2 — Northern England, parts of Wales, coastal areas
• Zone 3 — Scotland, exposed upland, coastal headlands

Exposure category modifies Zone:

• Sheltered — below 10m height or in dense urban environment
• Normal — standard open ground
• Exposed — elevated sites, open fields, coastal

Getting the wind zone and exposure wrong will result in insufficient ties. Always check the postcode using eSP's built-in tool rather than estimating.

Retaining Compliance Sheets

TG20 Compliance Sheets should be:

• Generated before erection commences
• Filed in the scaffold register for the project
• Available on site for inspection (as part of the scaffold documentation pack)
• Retained for a minimum of 5 years after scaffold dismantling

During scaffolding inspections (which must occur at least every 7 days and after adverse weather), the inspector should confirm that the erected scaffold matches the parameters on the Compliance Sheet. Any deviation — a bay wider than specified, a tie omitted — must be rectified or a revised Compliance Sheet generated.

Frequently Asked Questions

Is a TG20 Compliance Sheet a legal requirement?

No, it is not specifically required by legislation. However, the Work at Height Regulations 2005 require that scaffolds be designed by a competent person. Using the TG20 eSP tool and retaining the Compliance Sheet is the standard industry method of demonstrating that competence. In the event of an incident, a contractor who has not generated a Compliance Sheet and has no other design evidence will face serious difficulty demonstrating that the scaffold was properly designed.

Can I use TG20:13 Compliance Sheets from old projects?

No. TG20:21 supersedes TG20:13. Any new scaffold should be calculated using the TG20:21 eSP tool. Old Compliance Sheets from TG20:13 are not valid for new projects, though they remain valid documentary evidence for scaffolds erected under that edition at the time.

Does TG20 cover system scaffolds (Layher, Harsco, etc.)?

No. TG20 is specifically for tube and fitting scaffolds using steel tube to BS EN 39:2001 and couplings to BS EN 74-1:2005. System scaffolds (frame and brace, cuplock, ringlock, etc.) have their own proprietary design data and must be designed in accordance with the manufacturer's technical documentation and BS EN 12810.

What tube and coupler standards does TG20 require?

TG20 is based on:

• Steel tube: BS EN 39:2001, Grade S235 or S275 (Grade 43A), 48.3mm OD, 4.0mm wall thickness
• Couplings: BS EN 74-1:2005 for right-angle couplers, swivel couplers, and sleeve couplers; putlog couplers to BS EN 74-1
• Any departure from these specifications (thinner wall tube, non-conforming fittings) takes the scaffold outside TG20 scope

Who can generate a TG20 Compliance Sheet?

Any registered eSP user can generate a Compliance Sheet. There is no requirement for the person generating it to hold a specific qualification, but the person responsible for the scaffold (typically the Scaffolding Supervisor or Contracts Manager) should verify that the input parameters are correct before the sheet is issued.

Regulations & Standards

• Work at Height Regulations 2005 (SI 2005/735) — scaffold design by competent person; TG20 eSP is the accepted evidence route

• BS EN 12811-1:2003 — Temporary works equipment — Scaffolds — Performance requirements and general design

• BS EN 12811-2:2004 — Temporary works equipment — Information on materials

• BS EN 39:2001 — Loose steel tubes for tube and coupler scaffolds; specification

• BS EN 74-1:2005 — Couplers, spigot pins, and baseplates for use in tube and coupler scaffolds and falsework

• NASC TG20:21 — Comprehensive Guide to Good Practice for Tube and Fitting Scaffolding (2021 edition)

• NASC SG6:17 — Loading of Scaffolds; duty class definitions

• CDM Regulations 2015 — temporary works design obligations

• NASC TG20 and eSP Tool — TG20:21 publication and eSP tool access

• HSE Scaffolding Guidance — HSE scaffold safety guidance

• BS EN 12811-1:2003 via BSI — standard for scaffold performance requirements

• nasc membership requirements — NASC audit requirements including TG20 compliance

• scaffold inspection records — how to retain and use scaffold documentation including compliance sheets

• scaffold loading limits — duty class loading requirements in detail

• work at height regs 2005 — WAH Regs 2005 obligations for scaffold design and inspection