The Golden Thread Explained: What Contractors Must Document

What is the golden thread?

The golden thread is a concept introduced by Dame Judith Hackitt's post-Grenfell review of building regulations and fire safety. Her 2018 report identified a systemic failure in the construction industry: information about how buildings are designed and built was routinely lost, fragmented, or inaccessible — meaning the people responsible for maintaining buildings safely had no accurate record of what was actually built.

The Building Safety Act 2022 made the golden thread a legal requirement for higher-risk buildings (HRBs). Sections 85–88 of the Act establish the duty to create, maintain and hand over a structured information record throughout the design, construction and occupation phases of an HRB.

The golden thread is not a single document. It is the totality of information about a building, maintained in a structured format so that:

• The right people can access the right information at the right time
• Changes to the design or structure are recorded and traceable
• The building's "as-built" condition is accurately documented for whoever manages it after occupation

What information must it contain?

The Building Safety (Information and Records) Regulations set out the categories of information that must be included in the golden thread. During the design and construction phase (the period that most contractors are concerned with), this includes:

• Design information — architectural drawings, structural calculations, fire strategy documents, specifications for all materials and products that affect building safety
• Planning and building control records — planning permission, Gateway 2 approval from the Building Safety Regulator, Building Regulations approval
• Construction information — method statements, inspection records, test results, site surveys
• Product and material information — specifications, test certificates, installation records for safety-critical products (cladding, fire doors, structural elements, fire-stopping)
• Change records — any changes made during construction that deviate from the approved design, with the reason for the change and who approved it
• Dutyholder records — written appointments of the principal contractor, principal designer, and other contractors; evidence of their competence
• Health and safety file — the Construction (Design and Management) Regulations 2015 health and safety file, which forms part of the golden thread

Who is responsible for maintaining it?

Responsibility for the golden thread is shared across dutyholder roles, but the principal contractor has primary responsibility for the construction-phase information.

Specifically, if you are appointed principal contractor on an HRB project, you are responsible for:

• Creating and maintaining the construction-phase elements of the golden thread
• Ensuring your subcontractors provide the information required for their elements of the work
• Recording changes to the design or specification during construction
• Ensuring the golden thread information is kept in a form that is accessible and retrievable
• Handing over a complete and accurate golden thread to the principal designer (who coordinates the overall handover) at practical completion

The principal designer is responsible for coordinating the design-phase information and the overall structure of the golden thread. But on many SME projects — particularly where the main contractor is appointed before design is complete — the boundary between PC and PD responsibilities can overlap. The written appointments should define clearly who is responsible for what.

When does it need to be updated?

The golden thread is a live document, not a one-off production. It must be updated whenever:

• A change is made to the design or specification — particularly for safety-critical elements
• A product or material is substituted — the new product must be specified and the change assessed
• A significant construction event occurs — completion of a floor, installation of fire-stopping, cladding installation
• An inspection result is obtained — Building Regulations inspections, fire strategy sign-offs, structural inspections
• A dutyholder appointment changes — if the PC or PD changes during the project, this must be recorded

For HRBs, some changes require notification to the Building Safety Regulator before they can be made. Under the Building Safety Act's gateway regime, changes to anything specified in the Gateway 2 application that could affect compliance with the Building Regulations generally require BSR approval. Making such changes without BSR approval can constitute a criminal offence on HRB projects specifically — see the official gov.uk guidance or take legal advice for how this applies to your project.

Digital vs paper: what format is required?

The Building Safety Act does not mandate a specific digital platform for the golden thread. However, the statutory guidance strongly encourages digital formats because paper records do not reliably meet the accessibility, retrievability and durability requirements of the legislation.

The key characteristics required are:

• Accessible — the information must be retrievable by the people who need it, at the time they need it
• Accurate — the record must reflect the building as actually built, not as designed
• Proportionate — the level of detail should be appropriate to the safety risk (fire-stopping details matter more than paint colour)
• Durable — the information must survive the life of the building. Paper records in site offices do not meet this standard
• Searchable and structured — random document collections do not constitute a golden thread

Common digital approaches include Building Information Modelling (BIM) platforms, dedicated golden thread software, or structured document management systems with clear naming conventions and version control.

Handover: what happens at completion?

At practical completion, the golden thread must be handed over to the "accountable person" — the entity responsible for managing the occupied building's safety. On most residential developments, this will be the client, a management company, or a residents' management company.

The handover package must be sufficiently complete that the accountable person can:

• Understand what was built and how it works
• Maintain the building safely and in compliance with the Building Safety Act's in-occupation regime
• Identify any safety-critical systems and how to maintain them
• Respond to resident safety concerns with accurate information about the building's structure and systems

The principal designer is responsible for coordinating the overall handover package, but if you hold the principal contractor role, you are responsible for ensuring the construction-phase information is complete and in the agreed format before practical completion. Building Safety Regulator Gateway 3 sign-off (required before an HRB can be occupied) is generally understood to depend on a satisfactory golden thread handover — confirm the current requirements with the BSR.

Common mistakes contractors make

• Treating the golden thread as end-of-project admin. It must be maintained throughout construction, not assembled retrospectively at handover. Retrospective assembly is unreliable and often incomplete.
• Not specifying what subcontractors must provide. Your subcontracts must include requirements for subcontractors to provide information for the golden thread — product specifications, test certificates, as-installed drawings. If you don't specify it upfront, you won't get it.
• Informal change management. Verbal instructions to change a product or method are not sufficient. Every change must be documented, assessed and (where required) approved by the BSR before it is made.
• Confusing the health and safety file with the golden thread. The H&S file (required under CDM 2015) is part of the golden thread, but the golden thread is significantly more extensive — particularly for the fire strategy and building safety elements.
• Assuming the principal designer is handling it. The PD coordinates the golden thread, but the PC is responsible for the construction-phase records. If you don't maintain them, no one else will.

How Subchecked helps

One element of the golden thread that is generally treated as mandatory is dutyholder records — specifically, evidence that you verified the competence of every contractor and subcontractor before they were appointed. This reflects both BSA requirements and the Building Regulations (Amendment) Regulations 2023 — check how these apply to your specific project.

Subchecked provides the automated, timestamped verification records that form the subcontractor competence element of your golden thread. For each subcontractor:

• CSCS card verification (confirmed against the CITB register)
• CIS status verification (confirmed via HMRC Government Gateway)
• Right to Work verification (document capture with timestamp)
• Insurance confirmation (insurer-confirmed or document-level)
• Trade-specific checks (Gas Safe, NICEIC/NAPIT for relevant trades)

These records are stored in Subchecked and can be exported as part of your golden thread handover package — showing, for every subcontractor who worked on the project, what was checked, when, and what the result was. It doesn't cover all elements of the golden thread, but it covers the subcontractor competence verification records that regulators specifically look for.