8th October, 2020

Can You Have Two Principal Contractors On One Site?

Any construction project with more than one contractor needs a principal contractor appointing under CDM. There should only be one principal contractor on a project. But what if your site has multiple projects? Can you appoint more than one principal contractor? Let's see what the regulations say.

Can You Have Two Principal Contractors On One Site? header image

As a general rule, you can only have one principal contractor on a construction project at any one time, under CDM. And to keep things simple, you really shouldn't look to change the principal contractor during the project, unless you really need to. Because pretty much every CDM document will need to be re-created, re-communicated, and an additional handover of information will be required. This is an added cost and complexity to any project, which should be avoided.

So, one project, one principal contractor (more on that later).

But what if you have multiple projects on one site. With different teams, different activities, different clients even? Let's start with the appointment of principal contractors, under CDM. And the fact that each project can only have one principal contractor.

Each CDM project can only have one principal contractor

The principal contractor is the contractor in overall control of the construction phase. By definition then, there can only be one principal contractor. Because, if you had two, no one is in overall control.

In fact, the regulations are quite clear on this.

5.—(1) Where there is more than one contractor, or if it is reasonably foreseeable that more than one contractor will be working on a project at any time, the client must appoint in writing—

  1. a designer with control over the pre-construction phase as principal designer; and
  2. a contractor as principal contractor.

So, when a project involves more than one contractor, then a principal contractor must be appointed. Not several principal contractors. Not a few. Or a couple. A principal contractor. As in, one.

cdm principal contractor

“principal contractor” means the contractor appointed under regulation 5(1)(b) to perform the specified duties in regulations 12 to 14;

The Construction (Design and Management) Regulations 2015 Interpretation

The contractor. Again only one, as per the definition of the principal contractor under CDM. Even the F10 notification form only has space for the details of one principal contractor. One project, one principal contractor.

Since each construction site is usually one project, this means you can't usually have more than one principal contractor on site. But the question we are asking here isn't if you can have two principal contractors on one project (you can't), but can you have two principal contractors on one site? What about if your site is a factory, and you are going to have two separate projects? Or your site will have two new-build blocks of flats, and each block will be built by a different team?

Multiple projects

There's only one situation where you should start to think about having more than one principal contractor, and that's if you have more than one project.

Forgetting about the regulations for a moment, having more than one principal contractor just doesn't make much sense unless you have no choice. Communication on construction projects faces enough challenges without creating any more obstacles.

A key benefit of the principal contractor role is to have one main point of contact on your site during the construction phase. One point of contact that all of the contractors on the site can go to with any issues or concerns. One point of contact for the principal designer to liaise with. And one point of contact to answer the client's questions. One contractor in overall control of the site. One set of rules. One.

cdm duty holders diagram

If you add a second principal contractor, you don't really have a principal contractor at all. You're back to having multiple contractors, and the various conflicts that can come from that. Each looking out for their own interests, rather than one looking out for the overall success of the project. That's not to say contractors can't work well together (they can) but ultimately, different trades have different objectives and tasks to get done. And the whole need for a principal contractor is to have one contractor that can pull all of the different trades together, scheduling the work to deliver the project as a whole, rather than it's individual parts.

In light of this, the only time you should have two principal contractors on one site, is if you have two completely independent projects.

There may be occasions where two or more projects are taking place on the same site at the same time, but are run independently of one another. Whatever the circumstances, it is essential that there is clarity over who is in control during the construction phase in any part of the site at any given time. Where it is not possible for one principal contractor to be in overall control, those principal contractors involved must:

  1. cooperate with one another;
  2. coordinate their work; and
  3. take account of any shared interfaces between the activities of each project (eg shared traffic routes).

The CDM guidance says that if there are two (or more) projects on the site at the same time, there may be more than one principal contractor. But only where they are run independently of one another. And only where one principal contractor can't be in overall control.

By having two principal contractors, you can add extra complexity. There's additional coordination needed, because a construction site always has needs beyond its boundaries. There's deliveries, service connections, welfare needs, security, access. Some activities may extend beyond the site entrance. The two contractors need to cooperate with each other. Each site will need to comply with CDM seperately. Each project run independently.

If the projects are similar activities, run at the same time, there may be cost, productivity, and safety benefits to having one principal contractor. But this will need to be decided on a case-by-case basis, and if two projects are truly independent, it may be better to have two principal contractors, each within their different areas of expertise. Providing they can work together to ensure that the two projects can be carried out safely and not negatively impact on the other.


If you need help complying with CDM duties, get our free CDM duty holder guides for more support. And check if your project is CDM ready with the CDM compliance checklist.

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This article was written by Emma at HASpod. Emma has over 10 years experience in health and safety and BSc (Hons) Construction Management. She is NEBOSH qualified and Tech IOSH.

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