Construction site records are no longer an optional admin task, on Building Safety Regulator projects they are legal evidence. Subcontractors are central to this shift. On BSR-regulated sites, subcontractor evidence is not just paperwork,it is proof that work has been carried out safely, competently and in compliance with regulatory obligations.
Subcontractor evidence feeds directly into the Golden Thread, informs Gateway submissions and is used by the Regulator to assess whether a building can legally proceed through construction, reach completion and be safely occupied. In London, where complex interfaces, multi-trade packages and tight sequencing are the norm, missing or poor quality subcontractor evidence has become one of the most frequent causes of compliance failure.
This article explains what evidence subcontractors must provide on BSR projects, why it matters, how it must be structured, and what subcontractors and those who manage them must do to get this right in 2026 and beyond.
The regulatory context for subcontractor evidence
Under the Building Safety Act and associated Regulations, the Principal Contractor and Principal Designer are responsible for ensuring that all construction information required to demonstrate compliance is produced, controlled and made available to the Accountable Person and the Building Safety Regulator. Subcontractors play a critical role because they are the ones actually installing, inspecting and testing key life-safety systems and components.
The Regulator treats subcontractor evidence as safety-critical data, not optional records. Evidence must be verifiable, traceable and produced in a format that aligns with the wider Golden Thread information model. This changes decades of precedent where subcontractor information was loosely compiled or held in silos. On BSR projects, if it was not documented correctly, in the right format and linked into the compliance process, it did not happen.
What counts as subcontractor evidence
Evidence from subcontractors includes all records that demonstrate the quality, competence and compliance of work carried out under their scope. At a minimum, this must include:
This list is not exhaustive, but it represents the standard evidence set expected by the Regulator on all BSR-regulated sites in London.
The structure and quality of evidence
It is not enough to hand over a stack of random documents. Subcontractor evidence must meet minimum structural, quality and traceability standards.
Evidence must be:
Subcontractor evidence feeds directly into the Golden Thread, informs Gateway submissions and is used by the Regulator to assess whether a building can legally proceed through construction, reach completion and be safely occupied. In London, where complex interfaces, multi-trade packages and tight sequencing are the norm, missing or poor quality subcontractor evidence has become one of the most frequent causes of compliance failure.
This article explains what evidence subcontractors must provide on BSR projects, why it matters, how it must be structured, and what subcontractors and those who manage them must do to get this right in 2026 and beyond.
The regulatory context for subcontractor evidence
Under the Building Safety Act and associated Regulations, the Principal Contractor and Principal Designer are responsible for ensuring that all construction information required to demonstrate compliance is produced, controlled and made available to the Accountable Person and the Building Safety Regulator. Subcontractors play a critical role because they are the ones actually installing, inspecting and testing key life-safety systems and components.
The Regulator treats subcontractor evidence as safety-critical data, not optional records. Evidence must be verifiable, traceable and produced in a format that aligns with the wider Golden Thread information model. This changes decades of precedent where subcontractor information was loosely compiled or held in silos. On BSR projects, if it was not documented correctly, in the right format and linked into the compliance process, it did not happen.
What counts as subcontractor evidence
Evidence from subcontractors includes all records that demonstrate the quality, competence and compliance of work carried out under their scope. At a minimum, this must include:
- Installation records showing exactly what was installed, where, when and by whom. These must be linked to contract scope and design intent.
- Inspection and test results including calibrated test equipment outputs, acceptance criteria and sign-off by competent personnel.
- Competence records for the personnel performing or supervising the work. This must demonstrate that individuals are legally and professionally capable of carrying out the specific task under the Building Safety Act regime.
- Design compliance documentation where the subcontractor is responsible for design elements, including shop drawings, coordination records and change control approvals.
- Non-conformance reports and corrective action evidence where work deviated from specification and corrective steps were taken and verified.
- Photo, video and measurement metadata tied to the record itself; simply having an undated image on a phone is not sufficient. Metadata must be integrated into the document control environment.
This list is not exhaustive, but it represents the standard evidence set expected by the Regulator on all BSR-regulated sites in London.
The structure and quality of evidence
It is not enough to hand over a stack of random documents. Subcontractor evidence must meet minimum structural, quality and traceability standards.
Evidence must be:
- Linked to design and contract scope. Each record should clearly connect the physical work to the associated design requirement or regulatory clause.
- Timestamped and auditable. Each record must include date/time and be uniquely identifiable within the project’s document control system.
- Controlled via versioning. Subcontractors must not simply drop files into a shared folder; evidence must be versioned, controlled and locked once approved.
- Accessible via the Golden Thread environment. Records must be integrated into the project’s controlled information ecosystem, not hidden in personal laptops, emails or unstructured drives.
Substandard evidence (incomplete records, ambiguous sign-offs, missing test criteria) leads directly to compliance risk, Gateway delays, inspections that fail and enforcement action.
Delivery expectations for subcontractors
By 2026, the days of paper handover binders and ad-hoc email submissions are over. The Building Safety Regulator expects evidence to be delivered in structured, consistent digital formats that can be audited and quality-assured.
Subcontractors are expected to provide:
- Electronic inspection and test reports that are exportable from a controlled environment.
- Digital competence profiles for personnel, linked to recognised standards.
- Certification and compliance declarations where required under Building Regulations and BSR frameworks.
- Evidence metadata that allows the Principal Contractor to demonstrate traceability and version history.
Most London Tier 1s now mandate that subcontractor evidence be produced directly into the common data environment (CDE). Subcontractors that insist on parallel systems will find their evidence rejected or returned for rework.
Interfaces and coordination — the common failure point
On multi-trade London projects, the most common evidence failures occur at the boundaries, where two or more subcontractors overlap or where scope transitions occur.
Examples include:
- Mechanical and electrical interfaces where penetrations cross fire separations.
- Structural fixings installed before fire stopping evidence is generated.
- Integrated systems (e.g., HVAC + smoke control) with separate subcontractor reporting protocols.
These interface issues are not just coordination problems, they are evidence problems. If two subcontractors produce conflicting records, or if one party’s test regime does not align with another’s record set, the evidence cannot be accepted.
BSR projects must build integrated evidence streams and hold interface workshops to align test criteria, sign-off protocols and common naming conventions.
What happens if subcontractor evidence is missing or deficient
The Building Safety Regulator treats missing or deficient subcontractor evidence as a safety risk. On live projects this can lead to:
- Gateway delays at Gateway 2 and Gateway 3
- Requests for information issued by the Regulator with compliance deadlines
- Enforcement notices and work stoppages
- Rejection of completion evidence packs
- Legal exposure for subcontractors and principal dutyholders
On occupied buildings, missing or inadequate evidence can trigger compliance investigations, improvement notices, or criminal liability for dutyholders under the Building Safety Act and other safety legislation.
Who ultimately owns the evidence
While subcontractors produce the evidence, accountability rests with the Principal Contractor and Principal Designer during construction and with the Accountable Person after handover. Subcontractors have a duty to provide, but dutyholders carry legal responsibility for its quality, access and preservation.
This means subcontractors must work with Principal Contractors, design teams and information managers early (ideally at tender stage) to agree evidence protocols, formats and delivery milestones.
What this means for subcontractors in 2026
For subcontractors on BSR-regulated projects in London, evidence provision is now a core deliverable, not an add-on. Meeting this requirement means:
- Investing in digital evidence capture systems
- Training staff on BSR evidence standards
- Aligning reporting protocols with Principal Contractor systems
- Engaging early with design and information control teams
- Treating evidence delivery as an integrated part of quality and safety
Subcontractors that fail to adapt will find themselves excluded from competitive frameworks, rejected at Gateway reviews, or liable for rework costs.
Conclusion — evidence is proof of legal existence
On Building Safety Regulator projects, subcontractor evidence is not just documentation, it is legal proof that work was done in compliance with regulatory requirements. Subcontractors that understand this are not just delivering installation work; they are delivering legal compliance.
Getting evidence right protects people, projects, margins and reputations. It also protects the very existence of the building in law. In the new era of the Building Safety Act, evidence is not optional, it is essential.
Image © London Construction Magazine Limited
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
