WhatsApp on site and the golden thread: the decisions nobody wrote down

Why do site decisions end up in WhatsApp?

Because it is the only channel everyone on the job already has. There is no licence to buy, no account to set up, no training session and no password to reset at seven in the morning. A photograph takes two taps and arrives at a size that works on a weak signal. A voice note works with gloves on.

That matters more than it sounds, because of who is in those groups. A project information system gets rolled out to the principal contractor's own staff. It rarely reaches the groundworks gang, the scaffolder's foreman, the cladding subcontractor two tiers down, the supplier's driver or the client's facilities manager. Those people are central to the work and peripheral to the licence count. They stay in the chat, and so does the conversation.

The result on most projects is that the fastest, most complete and most candid account of what happened is held on personal phones, by people who may have moved on long before anyone asks.

Can a message actually change what gets built?

Regularly. Somebody asks whether a detail can be varied because the product has not arrived. A photograph of a marked up drawing comes back with a line of text under it. The work proceeds.

That is a design change, whatever application it happened in. On a higher-risk building the next question is whether it was the kind of change that required notice or approval before the work went ahead, under the Building (Higher-Risk Buildings Procedures) (England) Regulations 2023, and whether anyone treated it as one at the time. A change that was never recognised as a change does not get assessed, does not get notified, and does not reach the information that is handed over at the end.

It is worth being clear that the law already treats these exchanges as real. In Jaevee Homes Ltd v Fincham [2025] EWHC 942 (TCC), the Technology and Construction Court held that a demolition contract was formed on 17 May 2023 by a WhatsApp exchange in which the contractor asked whether the job was his so he could start getting organised, and received the single word yes in reply. A formal sub-contract emailed nine days later, at a different figure, was never acknowledged by the other side and did not apply. Around 195,000 pounds was invoiced and the balance was fought over on the basis of a contract that existed only in a phone.

Nothing about that decision is peculiar to messaging apps. English law has never required most construction contracts to take a particular form. What has changed is where the conversation now happens.

What does the golden thread expect of that information?

The golden thread is not a folder handed over at the end. It is the information that explains why the building is safe, created as the building is designed and built, kept accurate as things change, and passed on in a form the people operating the building can actually use. That expectation runs through the Building Safety Act 2022 and it comes directly from the finding in Building a Safer Future that, when things went wrong, nobody could reliably say what had been built, why, or on whose authority.

Read that finding next to a site WhatsApp group and the problem states itself. The group is often the only place that records why something was done. It is also the place least likely to survive, least likely to be structured, and least likely to be handed to anyone.

There is more on what the thread has to hold, and the discipline behind it, in the golden thread guide.

Where does this break down in practice?

At four points, and they get progressively more expensive.

Stage	What goes into the chat	What it costs if it stays there
Gateway 2 and design development	Queries about details and product substitutions, answered informally	The approved design and the intended design quietly diverge before work starts
During construction	Instructions, sequence changes, approvals of samples and setting out	Change control never sees a change, so it is neither assessed nor notified
Gateway 3 and handover	The reasoning behind what was actually installed	Evidence is reconstructed from memory and camera rolls, and applications stall
Occupation and the safety case	Why a departure was accepted, and by whom	The accountable person inherits a building whose information does not match it

The pattern is the same at each stage. The decision is real, the record is not, and the gap only becomes visible when somebody has to explain the building to a regulator or a court.

The Gateway 3 stage is where most projects feel it first, because collation is not the same as archaeology. There is a fuller treatment of that in site records as Gateway 3 evidence, and of what counts as a change in Gateway 2 change control.

What happens if someone deletes the messages?

It gets worse, not better. Messages are disclosable in litigation, including messages held on personal devices that are used for work, and the same material is routinely produced in adjudication.

Destroying it once a dispute or an investigation is in prospect is treated as a serious matter in its own right. In Ocado Group plc v McKeeve a solicitor was found in criminal contempt of court and fined 25,000 pounds for telling a contact to delete a messaging application after a search order had been granted. The judgment is published in full.

Whatever a thread contains, deleting it converts a problem about the building into a problem about conduct.

What can a dutyholder do about it?

Four things, none of which is an instruction to stop using the app.

1. Name the project groups. Decide which groups are project groups and say so. A group for the job is a project record. A group for the five a side is not.
2. Tell people once, in writing. Say that messages in project groups are project records, may be retained and may be produced. It costs nothing and it changes how people write.
3. Make sure decisions leave the chat. A message can be where a decision starts. It cannot be the only place the decision exists. If it changed the building, it belongs in change control and in the information that will be handed over.
4. Capture the traffic rather than policing it. If moving a message into the record is a manual second job, it will be done for a fortnight and then it will not. Capture that happens without anyone remembering is the only kind that survives a busy project.

None of this is a statutory requirement in itself, and this page is information rather than legal advice. The statutory duties sit in the Building Safety Act 2022 and the procedural regulations, and what they require of a particular project depends on the building and the role. The practical point is narrower and hard to argue with: if the reason a building was built the way it was is sitting in a group chat, it is not in the golden thread, and at some point somebody is going to ask for it.