The highest level of independent design verification for scaffold and temporary works. Fully insured, fully independent.
CAT 3 (Category 3) is the highest level of independent design verification under BS 5975 for temporary works. It exists to provide maximum assurance that a scaffold or temporary works design is safe, adequate and compliant — by removing any organisational connection between the original designer and the checking engineer.
Unlike CAT 1 (a self-check by the original designer) and CAT 2 (a check by another engineer within the same organisation), a CAT 3 check requires a completely independent organisation to carry out a fully separate review. The checking engineer independently verifies the design brief, methodology, drawings and structural calculations without sight of the original calculation package.
This provides the highest level of impartiality and assurance. The checking engineer reaches their own independent conclusions about the adequacy of the design — not simply reviewing someone else's working.
A CAT 3 design check is typically required where the complexity or consequences of a scaffold design go beyond what can be adequately verified by an internal review. Common scenarios include:
Self-check by the original designer. An internal review of their own work. The lowest level of verification — no independence from the design process.
Checked by a different engineer within the same organisation. Provides a second pair of eyes but not full independence — the checker and designer share the same management structure.
Checked by a completely separate organisation with no involvement in the original design. The checker carries out fully independent calculations. This is the level Node Group provides.
Node Group provides fully insured, fully independent CAT 3 design checking for scaffold and temporary works across the UK and Ireland. Our checking engineers are specialist scaffold designers — not generalist structural engineers reviewing work outside their core discipline.
Our CAT 3 checking service is backed by professional indemnity insurance. Full cover for every independent check we issue.
Experience across Network Rail and other industry frameworks where CAT 3 checking is a contractual requirement.
Our team are specialist scaffold design engineers. Every check is carried out by engineers who design scaffolding full-time — not generalists.
Every check includes fully independent calculations — not a desktop review of the original design. We verify the design from first principles.
We prioritise turnaround without compromising rigour. Direct contact with the checking engineer throughout the process — no intermediaries.
Depends on complexity. Simple designs may be checked within days; complex temporary roofs or Network Rail projects may take longer. We prioritise turnaround without compromising the independence or rigour of the check.
No. A CAT 3 check is fully independent. The checking engineer carries out separate calculations and design verification without sight of the original calculation package. This is what distinguishes CAT 3 from CAT 1 and CAT 2.
Yes. Node Group's CAT 3 checking service is fully insured with professional indemnity cover.
Yes. We provide fully insured CAT 3 checking across Network Rail and other industry frameworks.