Does My Scaffold Need a Design?

One of the most common questions asked by scaffold contractors, site managers and temporary works coordinators is:

“Does this scaffold need a design?”

The answer depends on whether the scaffold can be demonstrated as compliant with recognised industry guidance such as TG20:21 or TG30:24.

Many scaffolds can be erected without a bespoke structural design because they fall within standard compliance guidance. However, when a scaffold exceeds those limits or introduces unusual loading conditions, a scaffold design may be required.

This guide explains when scaffold designs are needed, when compliance sheets are sufficient, and how to determine whether your scaffold falls outside standard guidance.

The Simple Answer

A scaffold generally does not require a bespoke design if it can be shown to comply with:

• TG20:21 (tube and fitting scaffolds)
• TG30:24 (system scaffolds)
• Manufacturer-specific guidance
• Standard loading and geometry limits

A scaffold may require a design if it falls outside these recognised compliance standards.

Many everyday scaffolds can be erected without a bespoke structural design because they fall within the scope of TG20:21, TG30:24 or manufacturer guidance. Typical examples include standard independent access scaffolds, birdcage scaffolds, loading bays, stair towers and mobile towers that remain within the permitted dimensions, loading limits and tie arrangements. In these cases, a TG20 or TG30 Compliance Sheet is often sufficient to demonstrate compliance, eliminating the need for separate engineering calculations or design drawings.

A scaffold design is usually required whenever the scaffold falls outside the scope of TG20:21, TG30:24 or manufacturer guidance. Common examples include cantilever scaffolds, large bridging scaffolds, temporary roofs, heavily loaded platforms, complex geometries, suspended scaffolds, significant sheeting or netting installations, and scaffolds with non-standard tie arrangements. These structures often introduce additional structural demands that cannot be verified using standard compliance guidance alone and therefore require assessment and design by a competent scaffold designer.

TG20:21 allows many tube and fitting scaffold configurations to be erected without a bespoke design.

However, TG20 specifically identifies situations where a scaffold is considered:

“Outside the Scope of TG20”

When this occurs, a compliance sheet alone is not sufficient.

The scaffold must be assessed by a competent scaffold designer.

Common TG20 design triggers include:

• Excessive lift heights
• Non-standard bay lengths
• Heavy duty loading
• Unusual tie arrangements
• Cantilever sections
• Bridges beyond permitted limits

TG30:24 provides compliance guidance for system scaffolds.

Like TG20, TG30 identifies circumstances where scaffolds exceed standard compliance parameters.

Factors that may require a design include:

• Manufacturer limitations
• Unsupported configurations
• Excessive loading
• Complex geometry
• Wind-sensitive structures

In these situations, additional engineering input may be necessary.

Responsibility is often shared between several parties:

Scaffold Contractor

Must determine whether the scaffold can be erected within TG20 or TG30 guidance.

Temporary Works Coordinator

May request evidence of compliance or design documentation.

Principal Contractor

Must ensure suitable temporary works procedures are followed.

Scaffold Designer

Provides engineering calculations and drawings where required.

If a scaffold requires a bespoke design, the designer will typically need details of the scaffold geometry, including its height, length, width and lift heights, together with the intended use and loading requirements. Information about the site, structure being accessed, tie locations, ground conditions, environmental exposure, and any sheeting, netting or temporary roof requirements is also essential. Providing accurate project information at the outset helps ensure the scaffold design is safe, compliant and delivered efficiently.

Determining whether a scaffold requires a design can be challenging, particularly on complex projects.

SMART Compliance helps scaffold contractors:

• Verify TG20 compliance
• Identify when scaffolds fall outside guidance
• Generate compliance sheets
• Maintain auditable records
• Simplify compliance checks

Developed by CADS, the engineering software company involved in the development of both TG20:21 and TG30:24, SMART Compliance provides a faster and more reliable way to assess scaffold compliance.