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Reimagining AEC is Dr Sepehr Abrishami's independent podcast on how the built environment handles information. Each episode takes one subject from digital construction, from the ISO 19650 series and the common data environment to the golden thread, soft landings and the arrival of artificial intelligence in design and surveying practice, and tells it as a single argument built on the published standards, guidance and evidence. Sepehr is a researcher and former architect who leads the Centre for AI in Construction and teaches building information modelling at master's level. The episodes are written for postgraduate students and practitioners who want the reasoning behind the rules, not a summary of them.
A safety decision about a high-rise home is useful later only if someone recorded why it was made. I am Dr Sepehr Abrishami, and having supervised doctoral researchers to completion I know that a thesis must give reasons for its choices. On Reimagining AEC, my own podcast, the subject here is the golden thread for higher-risk buildings in England, where the law sets duties that building information modelling, or BIM, practice can help to meet.
In guidance the Construction Leadership Council, or CLC, published in August 2024, a fire in a building leads alarm engineers to recommend changes to its alarm and smoke control systems. They base the recommendation on lessons from that fire, and the change is made. The guidance, my main source in this episode, then follows the building forward in time. One day someone new becomes responsible for the building. If the decision and its reasons were never recorded where that person would look, the guidance warns, they might unwittingly reverse the change and leave the building less safe. Nothing in the example questions the engineers' advice. What it tests is whether the reasons for acting on that advice survive in the record.
That case leads straight to my question. It asks which information must exist about a higher-risk building, who must hold it at each stage of the building's life, and how they must keep it so that its safety can be demonstrated. In England the law gives the answer a name, the golden thread, and here that phrase is a legal term with duties attached.
To answer the question, I will follow one fire door through the life of a residential tower. The tower exists only for this episode. What happens to its door follows examples the guidance itself gives, apart from one product substitution on site, which I have added. A fire door suits the purpose, because it must be accounted for when it is designed, installed and handed over, and every time it is inspected or replaced.
Following that door should equip you to explain where the golden thread comes from in law, and what the people who design and build such a tower must keep and pass on. It should also let you describe how those who manage the occupied tower use that information, and relate the rules on holding it to ISO 19650 practice. I take the answer in four parts: the law, then design and construction up to completion, then the occupied building, and finally how the information is managed and stored. I state the law as the guidance and official sources state it, and this is not legal advice.
The first part is the law, and it begins with a short history. Dame Judith Hackitt led an independent review of building regulations and fire safety after the Grenfell Tower fire in June 2017. Her final report, published in 2018, found significant gaps in key information about buildings, both while they were designed and built and while they were in use. She recommended an electronic record and called it the golden thread. In July 2021 the Building Regulations Advisory Committee, known as BRAC, published a report defining the golden thread and setting out its principles. The CLC guidance says both remain relevant. The Building Safety Act 2022 turned the recommendation into law, and the building control regime for higher-risk buildings started on the first of October 2023. The regulator responsible for all this has since changed, and I come to that change at the close of this part.
The guidance defines the golden thread in two halves. The first half is the information that allows someone to understand a building and keep it safe. The second half is the systems and processes that keep that information accurate, understandable, accessible and up to date. The law therefore asks for a way of working as well as a set of files. The information is electronic, specific to one building and its residents, and develops from design into occupation. The guidance is just as clear about what the golden thread is not. In her foreword, Dame Judith Hackitt writes that it is not intended to be a list of things to do for no real purpose, nor a repository for every detail of a building. It is not kept for the regulator alone, and it cannot be bought as a software product. Its focus is the two building safety risks the regime names, the spread of fire and structural failure. Keep the phrase about every detail in mind, because it returns when we reach ISO 19650.
These duties attach to higher-risk buildings, and the test differs slightly between two phases. During design and construction, a building is higher-risk if it is at least eighteen metres high or has at least seven storeys, and contains at least two residential units. A hospital or care home that meets the same height threshold is also included. In occupation, the regime covers buildings of that height with at least two residential units, so hospitals and care homes fall outside it. Their relevant fire safety information still passes at handover to the Responsible Person, who holds duties under fire safety law. The regime applies in England only, and for any real building you should check the detailed criteria on GOV.UK. Our tower, with flats on every floor, falls inside both tests.
The legal basis sits in two layers. The first is the Building Safety Act 2022 itself, primary legislation for which the Ministry of Housing, Communities and Local Government, or MHCLG, holds the policy. Part 3 of the Act covers design and construction and places duties on dutyholders, the client, designers and contractors, including a principal designer and a principal contractor. Part 4 covers occupation and places duties on accountable persons, the people and organisations who answer for an occupied building's safety, defined more closely in the third part. Through sections 33, 88, 89 and 90, they must create, obtain, update, maintain and share information and documents about the building, and that information is the golden thread.
The second layer is secondary legislation, where the detail sits, and three sets of regulations carry most of it. Statutory instrument 2023 number 909, the Higher-Risk Buildings Procedures Regulations 2023, governs design and construction. I will call these the procedures regulations. Two instruments govern occupation. Statutory instrument 2023 number 907, the Management of Safety Risks Regulations 2023, deals with how the information is kept and with the safety case report, the account of a building's safety risks and how they are managed. Statutory instrument 2024 number 41, the Keeping and Provision of Information Regulations 2024, deals with what accountable persons must keep and share, and I will call these the keeping and provision regulations. Four further sets cover changes to the Building Regulations 2010, registration, key building information and the definition of a higher-risk building, so read the legislation itself before any real decision.
When the guidance was written, the Building Safety Regulator, or BSR, sat inside the Health and Safety Executive, or HSE. Statutory instrument 2026 number 20, in force from the twenty-seventh of January 2026, established the BSR as a new body and made it the building safety regulator in place of HSE. The BSR and MHCLG announced that day that it had become an executive non-departmental public body, sponsored by the ministry. MHCLG's response of July 2026 on a single construction regulator named the BSR as that regulator's foundation, with implementation expected from 2028 and primary legislation still to come. That reform has its own episode, on the Single Construction Regulator. The golden thread duties themselves still sit in the Act and the regulations I have described. Everything that follows rests on this legal frame, in which the golden thread is information together with the processes that keep it accurate, aimed at fire and structural safety.
The second part follows the information through design and construction. The regime marks that route with gateways, the points at which the regulator checks the work, across four stages: design, construction, completion and occupation. Planning gateway one comes first, at the planning stage, and the fire statement produced there joins the golden thread. Gateway two is the building control approval application to the BSR. It is a stop and go point, and no building work can start without approval. The BSR's strategic plan for 2026 to 2027 reports that it has introduced staged gateway two applications. During construction, the golden thread records what is built and how, with changes controlled. Gateway three is the completion certificate application. A new higher-risk residential building cannot be occupied until it is registered, and registration needs that certificate. So before anyone moves in, the principal accountable person, usually the accountable person responsible for the structure and exterior, registers it and submits its key building information, a prescribed set of facts about it. Once it is occupied, that person prepares the safety case report. Through all four stages, safety occurrences must be reported to the BSR, a duty called mandatory occurrence reporting.
Up to completion, the golden thread rests with three dutyholders. The client makes sure that procedures for developing, managing and storing the information are in place. Regulation 31 of the procedures regulations requires the client to hold that information electronically and to give the principal designer and principal contractor access to it. The principal designer stores the designs and manages the information about design work, keeping it up to date and sharing what contractors need. Once work is about to start, the principal contractor manages the information about building work, in the system the client set up. Beneath all three sits competence. Under Part 2A of the Building Regulations 2010, everyone who designs or builds must be competent. The client checks this before appointing the principal designer and principal contractor, and records what it did in a competence declaration. For our door, this means one system in which its design records and its installation records will meet.
Alongside drawings and specifications, the gateway two application carries accompanying documents listed in the procedures regulations. Once the BSR approves the application, these become the agreed documents, a term that matters during construction. I sort them by purpose, a grouping of my own. One group governs how the work will be run. The construction control plan describes how compliance will be maintained and evidenced, and the change control plan sets out how changes are controlled and recorded, alongside the competence declaration and the mandatory occurrence reporting plan. The other group explains the building. The compliance statement sets out how each functional requirement will be met, and simply asserting compliance is not enough. The fire and emergency file explains the fire and structural safety strategies and their assumptions. A partial completion strategy is needed only where parts will be occupied while work continues.
Here the door enters at the design stage, in an example the guidance gives. Suppose the door is powered, so that less able people can pass through it freely, and it is also a compartment door that must stop the spread of fire and smoke. Free passage and fire separation make competing demands on one door. The golden thread must show how the design, if built, would comply with the building regulations, and the guidance sets four tests. The design identifies the building type and its safety risks. The products meet every relevant regulation, individually and as a system. They fit together without compromising the fabric or the compartmentation of the building. And the door can be safely installed, inspected, commissioned, operated and maintained. Before work starts, the information must show what will be built and how construction will be managed.
On site, the golden thread becomes evidence that the work conforms to the approved design, including approved changes. That evidence includes compliance of installations, full commissioning records, and operation and maintenance instructions that allow safe access later. Now the door meets the change I have added. Suppose the specified fire door set is replaced by a different product. Any change to the agreed documents is a controlled change, and that includes a change of organisation or personnel as well as a change of design. The substitution then passes through four actions in order. The principal contractor records it in the change control log. The client's procedures assess its impact. Where the regulations require it, the BSR is notified. Every change is recorded, but not every change is notifiable. Finally the agreed documents are updated, since their latest versions go to the BSR at gateway three. Mandatory occurrence reporting runs separately. Under its plan, any incident, or risk of an incident, that could cause structural failure or the spread of fire or smoke is recorded and reported to the BSR. The test is whether it could seriously harm a significant number of people.
At completion the golden thread changes hands, and that moment has two sides. On one side, the client makes a signed, written completion certificate application. Alongside a description of the work, it carries the completion date, the as-built plans, the change control log, the latest agreed documents and the client's signed statement. It also needs confirmation from the receiving person that they have the golden thread. On the other side, the client hands the golden thread to the principal accountable person. For non-residential parts, such as a hospital, only the relevant fire safety information goes, to the Responsible Person. The package includes copies of the application, its documents and the completion certificate, with extracts on Parts B, F, L and O of the Building Regulations, which cover fire safety, ventilation, energy and overheating. The receiver confirms that the information is received, accessible and usable, then judges which items remain golden thread information. The rest, the guidance notes, is very likely to be of significant value for operation and maintenance. Clients of buildings under the transitional arrangements must hand over fire safety information, but not golden thread information. By completion, then, the dutyholders have built the golden thread through gateways two and three, and our substituted door set is on record before the thread passes on.
The third part begins once people live in the tower, when responsibility for the golden thread passes to accountable persons. Section 72 of the Act defines the accountable person, usually as someone who holds a legal estate in possession in any part of the common parts, or who has a legal obligation to repair them. That is often an organisation, such as a social housing provider, a freeholder, a resident management company or a right to manage body. Where there is only one, it is the principal accountable person. Where there are several, the principal accountable person is the one responsible for repairing the structure and exterior. All of them must coordinate and share golden thread information, or the principal accountable person cannot produce a sound safety case report. One limit deserves close attention. An accountable person may employ a managing agent or commission specialists, but cannot delegate the legal obligation, and the liability stays with them. When an accountable person leaves the role, the golden thread information passes to the new one, apart from commercially sensitive material that is not significant for safety.
What they must keep is set out in Schedule 1 of the keeping and provision regulations, which the guidance groups under six headings, and two principles sit behind them. The first is that the record describes the building and its compliance, starting with the key building information, which the principal accountable person must submit to the BSR within twenty-eight days of registering. The second is that the record shows how safety is managed and how residents are involved, for example through the evacuation strategy and the resident engagement strategy. Much of this already exists, though perhaps not in the prescribed form. A change to registration information must reach the BSR within fourteen days, and a change to key building information within twenty-eight days.
Now the door returns, through the whole building approach the guidance asks of accountable persons, which treats the building as one system rather than a set of independent parts. The guidance's own example is the fire door. A fire door is one of many fire doors, and it is also part of the compartmentation. It helps contain a fire in the compartment where it starts and protects the next compartment, which may be an escape route or a place of refuge for disabled people. Annex D of the guidance sets out an example fire door record in five groups, and here is how it would read for our door. Asset data says what the door is and what it protects, from its location and compartments to its design intent and linked systems. Documents prove its certification and correct installation. Competence names who fitted it and their formal competence. Maintenance records each check, the actions that followed and who manages them. Access says where the record is held, who updates it, who reads it and who receives it. Then the guidance adds a change. Suppose a door with a thirty-minute fire rating is replaced by one rated for sixty minutes. The record must capture when the work was carried out, by whom, the evidence of their competence, who decided the door should change, and why.
In occupation, the main decisions about safety are set out in the safety case report. Section 85 of the Act requires the principal accountable person to prepare one as soon as reasonably practicable after the building is occupied, or after they become responsible if that is later. It contains the assessments of building safety risks made under section 83, and a description of the steps taken under section 84 to manage them. Regulation 5 of the management of safety risks regulations sets its content, and the guidance traces each part to the golden thread items behind it. Part of the report says what the building is and what could go wrong, and part says what is being done about it. The description of the building draws on its registration, key building information, design and completion documents. The risk scenarios draw on fire safety management, structural risks and risk assessments. The account of how section 84 is met, the system for managing safety and the emergency plans draw on the evacuation strategy, occurrence reporting, complaints and resident engagement. Our door's record would inform both parts, as part of the compartmentation the risk scenarios rely on and as evidence that it is maintained.
The BSR usually assesses the report when it determines an application for a building assessment certificate, its judgement of whether building safety duties are being met in an occupied building. That process began in April 2024, and the guidance expects it to take about five years to process all existing higher-risk buildings for the first time. The BSR will not routinely ask to review the golden thread, but the guidance warns that an inaccurate golden thread is likely to mean an inaccurate report, which will prompt further investigation.
The golden thread is shared as well as kept. Part 3 of the keeping and provision regulations sets out who must receive information and when, and two principles organise the recipients. The first is that people who live with the risks are entitled to understand them. Residents and owners of flats are entitled to prescribed information and can request further documents. That information must be understandable, so a fire risk assessment, for instance, may need a plain English summary, and residents need not receive it electronically. The second is that anyone taking on responsibility for the building, or part of it, receives what that responsibility needs. A new accountable person receives everything, and a client planning building work receives information about the part affected. All sharing must still respect security, commercial confidentiality and data protection. Keeping, sharing and reporting therefore form one duty for accountable persons, and their safety case report can be no more reliable than the golden thread beneath it.
The fourth part asks how the information should be held. No particular format or software is prescribed. Instead the information must meet eight principles. They are set for design and construction in regulation 31 of the procedures regulations, and for occupation in regulation 7 of the management of safety risks regulations, which omits up to date because the Act already requires it. I sort the eight into two groups, again my own. The first group is about reaching and using the information. Accessible means provided as soon as reasonably practicable to those who need it. Electronic allows any format the receiver can open and read. Transferable means passing between platforms and owners without loss or corruption. Understandable means clear to its users, with plain English for residents. The second group is about trusting the information. Accountable means each change records who made it and when. Accurate depends on change control. Secure means protected from unauthorised access. Up to date applies so far as possible, because some records, such as plans on completion, are a fixed historic record. Several of these will sound familiar if you know ISO 19650.
That link needs care, because the CLC guidance does not mention ISO 19650. The bridge comes from two sources it relies on. The first is the BRAC report of 2021. That report encourages common data environments, or CDEs, the agreed workflows and tools through which information is managed, as a way to keep a single source of truth. It also says the UK BIM Framework could support the golden thread. In May 2025 nima, formerly the UK BIM Alliance, announced that the framework had been renamed the IMI Framework, after the Information Management Initiative. The second source is BS 8644-1 of 2022, on the digital management of fire safety information. The guidance cites it, and the British Standards Institution, or BSI, says it is intended to be read with the ISO 19650 series. So the links I draw next are my interpretation, not the guidance's.
Three correspondences carry most of the weight. The first concerns what to hold. The client defines the golden thread content for each project. The ISO 19650 way of doing that is through asset information requirements and exchange information requirements, AIR and EIR, under ISO 19650-2 of 2018 and ISO 19650-3 of 2020. The guidance's warning against a repository for every detail matches the level of information need, now set out in ISO 7817-1 of 2024. The second correspondence concerns trust. The accountable principle matches clause five point one point seven of ISO 19650-2, under which the CDE records the user and the date whenever an information container, a named set of information, changes state. Security maps to ISO 19650-5 of 2020, the security-minded approach to information management. The third concerns handover, where transfer without loss matches the move from the project information model to the asset information model under ISO 19650-2 and ISO 19650-3. If our tower's information were run that way, the CDE would show who changed the door's record and when. The Act does not require ISO 19650, although public clients may require it by contract. In March 2026 nima reported that revised drafts of ISO 19650 Parts 1 and 2 had gone out for public comment, and the 2018 editions remain in force.
Annex D of the guidance also speaks to organisations that hold many higher-risk buildings. Golden thread information can sit in more than one system, so existing systems may already meet the requirements. Three expectations follow. Accountable persons should know which information is static, such as the fire resistance of compartment walls, and which is dynamic, such as the results of testing fire doors. They should set out formally who updates, maintains and reviews each part. And they should record why decisions were made, so that successors can rely on them. The alarm example from the start sits here, under the duty of accountable persons to set out why they made their decisions. The engineers' recommendation becomes useful golden thread information only when the decision and its reasons are written where a future accountable person will look, and our door's sixty-minute replacement carries the same requirement. The guidance places all of this inside a risk management system built on the plan, do, check, act cycle.
The guidance also explains why the golden thread asks so much of accountable persons, by quoting Dame Judith Hackitt's interim report of 2017. That report found "a widespread culture in relation to building and fire standards of waiting to be told what to do by regulators rather than taking responsibility for building to correct standards." The golden thread requirements are meant to change that culture. What the law fixes, in the end, is eight principles rather than a format, and ISO 19650 practice offers one tested way to meet several of them, though the law does not require it.
That draws the episode together, and brings back the door. It was designed as part of a system that must allow free passage and stop fire. It was installed with evidence, substituted under change control, handed over at gateway three, recorded in the occupied building's golden thread, and replaced with its reasons on file. That route answers the opening question. The information that must exist is whatever allows someone to understand the building and keep it safe from the spread of fire and structural failure, from design onwards. Dutyholders hold it first, and accountable persons hold it once people live there. And it must be kept to the eight principles, from accessible to up to date.
If you work on a higher-risk building, treat the golden thread as information together with the processes that keep it accurate, because a store of files without those processes does not meet the definition. Know which instrument governs which phase, with the procedures regulations for design and construction and the two occupation regulations for keeping and sharing, and remember that the BSR now stands outside HSE. And where your organisation already works to ISO 19650, its requirements, its CDE and its security-minded approach can help meet the principles, provided you remember that the law asks for the outcome and leaves the method to you.
For reading, start with the CLC guidance, then the Act and the three main sets of regulations on legislation.gov.uk, which holds the current text. The episodes on the Single Construction Regulator, on the common data environment and on information management in the operational phase sit closest to this one.
My name is Dr Sepehr Abrishami, and the last word of this episode of Reimagining AEC goes to the residents of buildings like our tower. Whoever follows you on such a building, as designer, contractor, manager or researcher, will depend on the reasons you write down, and so will they.