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Insight · Health and safety

When you become the principal
contractor without being told.

The duty attaches to a role, not to the size of the firm, and a second contractor arriving on site is enough to trigger it. What lands on you, and what happens when the client never appointed anybody.

Published ·5 min read·Written by Unibuild

Under regulation 5 of CDM 2015, a client must appoint a principal designer and a principal contractor in writing wherever more than one contractor is, or is reasonably foreseeable to be, working on a project at any time. The trigger is the number of contractors, not the size, value or duration of the job. Where the client makes no appointment, the client must fulfil those duties itself.

The trigger is smaller than people expect

Most firms carry a rough idea that CDM's heavier duties attach to large projects, notifiable projects, or jobs over some threshold. That is not what the regulations say.

The test in regulation 5 is simply whether more than one contractor is working on the project, or whether it is reasonably foreseeable that more than one will be, at any time. Two contractors is enough. A domestic-scale refurbishment with a builder and a separate electrician is enough. Value is irrelevant, duration is irrelevant, and notifiability is a different question with a different threshold.

Note the words "at any time" and "reasonably foreseeable". You do not escape the requirement by sequencing trades so that only one is on site at once, and you cannot ignore a second contractor you know perfectly well is coming in three weeks. The assessment is made about the project, in advance.

So a very large number of ordinary jobs require a principal contractor, and on a meaningful share of them nobody has formally appointed one.

What happens when nobody was appointed

This is the part reported wrongly almost everywhere, and getting it right changes the conversation you have with your client.

It is commonly said that where no appointment is made, the contractor becomes the principal contractor by default. That is not what regulation 5 provides. Where the client fails to appoint a principal designer, the client must fulfil the principal designer's duties. Where the client fails to appoint a principal contractor, the client must fulfil the principal contractor's duties.

The duty does not silently transfer to you because you happen to be the main trade on site. It stays with the client, who is very often a commercial client with no idea it has landed on them.

Two practical consequences. First, if you are the contractor on a job with no appointment, you have a strong and entirely reasonable case for raising it with the client in writing, because they are carrying duties they have not been told about. Second, none of that relieves you of your own duties as a contractor under regulation 15, which are substantial in their own right and apply regardless of who is principal contractor.

The duty does not drift onto whoever is biggest on site. It sits with the client until the client appoints somebody, which is usually news to the client.

What the role actually involves

If you are appointed, or if you are considering accepting the appointment, this is what you are taking on. It is more than a title on a form.

  • Plan, manage and monitor the construction phase, and coordinate it so that the work is carried out without risks to health and safety so far as reasonably practicable.
  • Prepare the construction phase plan before the construction phase begins, and review and revise it as the work changes. A plan written once and never touched is not a plan.
  • Liaise with the principal designer for the duration, including on design changes during construction, and pass information for the health and safety file.
  • Consult and engage with workers, which means genuine two-way communication rather than a notice on the cabin wall.
  • Secure the site and control access by unauthorised persons.
  • Ensure welfare facilities are provided and maintained throughout.
  • Ensure every contractor is informed of the minimum time allowed for planning and preparation before they start on site.

The recurring practical failure is not the plan. It is the monitoring and the record of it. Planning and managing generates documents naturally; monitoring generates them only if somebody deliberately records what they saw, when, and what they did about it.

Deciding whether to accept it

Where a client offers you the appointment, it is a commercial decision and there is a right answer more often than firms think.

Take it where you genuinely control the site: you set the sequence, you hold the gate, you decide who comes on. In that situation you are already doing most of the work, the appointment reflects reality, and having the role formally is better than having the responsibility informally.

Be careful where you do not control the site. If the client is running its own trades in alongside you, or a separate fit-out contractor answers only to the client, you would be accepting responsibility for coordinating people you cannot instruct. That is worth either declining, or accepting only with a written arrangement about who directs whom, and pricing for the management time it will actually take.

Whichever way it goes, get the appointment in writing. Regulation 5 requires it, and an informal understanding about who is principal contractor is exactly the thing that becomes contested after an incident.

Notifiable is a separate question

Worth separating clearly, because the two thresholds get conflated constantly.

Needing a principal contractor turns on more than one contractor. Being notifiable, which triggers the F10 notification to the HSE, turns on duration and workforce size instead. A project can require a principal contractor without being notifiable, and that combination is extremely common. Answer the two questions separately and in that order. The thresholds and the notification itself are covered in the CDM 2015 guide.

Where this touches the platform

The duties above are performed on site and Unibuild does not perform them. What it does is make them evidenced, which is the half most firms lose. Site diaries, progress photographs, permits and RAMS hang off one job record with the weather captured and the trades on site logged daily, so the monitoring that otherwise leaves no trace produces a dated record as a by-product of doing it. Health and safety records, inductions and training expiry sit against the same job rather than in a folder in a cabin that gets cleared at the end. The construction phase plan is still yours to write and revise; what changes is whether you can show, eighteen months later, that you were doing what it said.

The CDM 2015 guide Health and safety Project and site The CDM 2015 checklist

Where to start, on Monday

Take every job you currently have running and answer one question about each: is there more than one contractor on it. For the ones where the answer is yes, find the written appointment. Where there is no written appointment, that is not a filing gap, it is a live position in which the client holds duties it does not know it has.

Raise it in writing. It is a short, unremarkable email, it costs you nothing, and it is the difference between a well-run job and a conversation nobody wants to have after an incident.

Asked most often

The follow-up questions.

The full duty holder picture is in the CDM 2015 guide, with a working list in the checklist.

When is a principal contractor required under CDM 2015?+
Wherever more than one contractor is working on a project, or where it is reasonably foreseeable that more than one will be working on it at any time. Regulation 5 requires the client to appoint a principal designer and a principal contractor in writing, as soon as practicable and in any event before the construction phase begins. Project value and duration are irrelevant to this test.
Who is the principal contractor if the client never appointed one?+
The client. Regulation 5 provides that where a client fails to appoint a principal contractor, the client must fulfil the principal contractor's duties. It is commonly but wrongly said that the main contractor takes the role by default. The duty does not transfer to the largest trade on site, although every contractor's own duties under regulation 15 still apply regardless.
Does two contractors really trigger CDM principal contractor duties?+
Yes. The regulation says more than one contractor, and it includes the reasonably foreseeable case, so sequencing trades so only one is on site at a time does not avoid it if you know a second is coming. A builder plus a separate electrician on a small refurbishment meets the test.
What are the principal contractor's main duties?+
Plan, manage, monitor and coordinate the construction phase; prepare the construction phase plan before work starts and revise it as the job changes; liaise with the principal designer including on design changes and information for the health and safety file; consult and engage with workers; secure the site against unauthorised access; ensure welfare facilities; and ensure every contractor knows the minimum time allowed for planning before starting.
Is a project needing a principal contractor the same as a notifiable project?+
No, and the two are frequently confused. Needing a principal contractor turns on there being more than one contractor. Being notifiable, which requires an F10 notification to the HSE, turns on the project's duration and workforce size. A project can require a principal contractor without being notifiable, and that combination is very common.
Should I accept a principal contractor appointment?+
Accept it where you genuinely control the site: you set the sequence, hold the gate and decide who comes on. Be cautious where the client runs its own trades alongside you or a separate contractor answers only to the client, because you would be accepting responsibility for coordinating people you cannot instruct. In that case either decline, or agree in writing who directs whom and price for the management time.
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