Can my subcontractor carry out Highways jobs under my NHSS 20 certification?

Posted on: 27/04/2026

Category: Product Certification

In short, No. A company certified to NHSS 20 cannot legally allow a subcontractor to work under its certification if that subcontractor is carrying out activities covered by the scheme. The subcontractor must normally hold its own NHSS certification for the relevant scheme.

  1. The core rule in NHSS / Specification for Highways Works

Under the Specification for Highways Works (SHW), organisations performing work covered by a National Highway Sector Scheme must be registered to that scheme themselves.

Critically:

  • The SHW does not allow a certified contractor to provide an “umbrella” for an uncertified subcontractor to carry out scheme-covered work.
  • If subcontractors are used, they must also be registered to the relevant NHSS scheme.

So if the subcontractor is executing steelwork activities covered by NHSS 20, they are expected to have their own NHSS 20 certification.

2. Why the rule exists

NHSS schemes are designed to ensure that every organisation performing the work has independently verified systems and competence, including:

Because of this: 

  • ISO 9001-based quality management
  • competent personnel and welding controls
  • documented procedures and records
  • audited processes by a UKAS-accredited certification body

NHSS 20 specifically demonstrates that the constructor has an independently certified QMS relevant to steelwork execution in transport infrastructure.

If subcontractors were allowed to operate under another company’s certificate, that independent verification would be lost.

    3. The practical exception (often misunderstood)

    There is one nuance that sometimes causes confusion:

    • A subcontractor can be used without NHSS certification if they are not performing activities covered by the scheme (e.g., minor support services).
    • But if they are executing the work covered by NHSS 20, they must be certified.

    So the key question is what work they are actually doing.

    Examples:

    Situation
    Allowed?

    NHSS 20 company subcontracts steel fabrication/erection to a non-NHSS 20 firm

    Not allowed

    NHSS 20 company subcontracts transport or plant hire

    Usually allowed

    NHSS 20 company subcontracts steelwork execution to another NHSS 20 contractor

    Allowed

    4. How auditors usually enforce this

    During NHSS audits, certification bodies typically check:

    • subcontractor registers 
    • supplier approval procedures
    • evidence that NHSS-covered work is done by certified organisations
    • competence records

    If a contractor allows uncertified subcontractors to perform scheme-covered activities, it can result in:

    • major non-conformities
    • suspension of NHSS certification
    • contract compliance issues

    In Conclusion

    A company holding NHSS 20 cannot legally allow a subcontractor to perform NHSS-covered steelwork under its certification. The subcontractor must normally hold its own NHSS 20 certification if it is carrying out those activities.