Golden thread proportionality

In short: The golden thread does not mean keeping every document a building has ever generated. The principle the regulator applies is proportionality - you keep the information that is relevant to building safety, structured so it is useful at each stage of the building's life, and you retire what is no longer relevant. "Proportionate" is not a licence to hold less than the law requires; for a higher-risk building the bar is still high. It means scoping to what matters for safety, and keeping it under review.

Where "proportionate" comes from

When the government set out how the golden thread would work, the Building Regulations Advisory Committee published ten principles to guide the legislation. The tenth is relevant and proportionate, and it says plainly that preserving the golden thread does not mean everything about a building and its history has to be kept and updated from inception to disposal. The objective of the golden thread is building safety - so if information is no longer relevant to building safety, it does not need to be kept.

That single principle answers the question almost every accountable person and RMC director asks first: how much is enough? The honest answer is that there is no fixed page count or document list that applies to every building. The test is relevance to the safety of your specific building and its specific risks.

The other nine principles still apply

Proportionality sits alongside the rest of the framework, not above it. The golden thread must still be accurate and trusted, a single source of truth, secure, simple to access, and durable over the life of the building. GOV.UK guidance sets the practical bar for how information is managed and stored: it must be kept digitally, secure from unauthorised access, available when someone needs it, presented so it can actually be used, written in plain English, GDPR-compliant, and act as the building's single source of truth. Proportionality tells you what to hold; these principles tell you how to hold it. A slimmer set of documents kept in scattered email folders still fails - because it is not structured, accessible or verifiable.

What proportionate looks like in practice

For an occupied high-rise residential building, the regulator expects the accountable person to keep the building's health and safety file, its safety case report, its resident engagement strategy, and its mandatory occurrence reporting system. Alongside these, you should keep what you have that supports the safety case: refurbishment records, information inherited from previous owners including inspection reports and maintenance history, and the standard the building was originally built to.

Proportionality shapes the depth of each of these rather than whether you hold them. A simple, well-understood building with a straightforward fire strategy needs less supporting detail than a complex building with a stay-put strategy, external wall issues, or a history of alterations. The information you keep should be sufficient to demonstrate that you understand and are managing the building's safety risks - no less, but no more padding than that. Information should be streamlined enough to be genuinely useful at the relevant stage of the building's life, and kept under review so it stays that way.

What you can retire

Because relevance is the test, information that no longer bears on the safety of the building does not have to be retained indefinitely. Superseded drawings for a system that has since been replaced, or records tied to a risk that has been designed out through remediation, can be archived or removed once they are genuinely no longer relevant - provided you keep the record of what changed and why, since that history is itself part of the safety story. The judgement should be documented: proportionality is a decision you make and can justify, not a gap you leave by accident.

Proportionality is being pushed further

The direction of travel is towards more proportionality, not less. The government has said it will consult on improving the proportionality of the building control process so that smaller, safety-critical works to higher-risk buildings are not held up by having to pass through the full building control regime for every minor change. Industry bodies are also producing practical, proportionate guidance to help owners and managers build and maintain a golden thread without over-engineering it. The principle is settling into something workable - but the duty to hold accurate, current, safety-relevant information has not softened.

The common mistake in both directions

Two failures show up repeatedly. The first is treating proportionality as an excuse to keep too little - a thin folder that cannot actually demonstrate how the building's risks are understood and managed, which will not survive scrutiny from the Building Safety Regulator. The second is the opposite: hoarding every document ever produced in an unstructured dump, on the theory that more is safer. That fails the accessibility and single-source-of-truth principles, and in practice makes it harder to find the information that matters when it is needed. Proportionate means deliberate: the right information, structured, current, and defensible.

How CTS and BuildSafe help

Getting proportionality right is a judgement call, and it is exactly the judgement CTS is set up to make. We assess your building against the Act's requirements, decide what is genuinely relevant to its safety, and structure it in the CTS BuildSafe platform - built around the information the Act requires, with version control, role-based access and an audit trail. That means you hold what you need to satisfy the Regulator, retire what you do not, and can show the reasoning behind both. For more on what the golden thread must contain, see our golden thread guide.

General information, not legal advice. Reviewed by the CTS building safety team.