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14th January, 2020

CDM 2015 For Only One Contractor

The Construction (Design and Management) Regulations (CDM) 2015 apply to every construction project, regardless of size or duration. No matter what type of work you do, from maintenance and odd-jobs to refurbishments and new builds, you need to know about CDM.

Usually, there will be 5 roles under CDM:

  • The Client
  • The Principal Designer
  • The Principal Contractor
  • Contractors
  • Designers

Not sure where to begin with CDM? Start with our CDM Regulations Summary blog post.

However, on projects with only one contractor, there are a few changes to the CDM duties that apply to the project. Before we go into those, it's important to check that your project really is a single contractor project.

A single contractor project is any project that will only involve one contractor, from start to finish. If the contractor appointed to do the work uses subcontractors, or the client brings in additional contractors at any stage, then the project is not a single contractor project.

Sometimes, a client may only appoint one contractor. But it is important to check if they will use subcontractors to complete the work. A scaffolder for access, or an electrician or gas engineer for example. If they do use other contractors, then the project would not be a single contractor project.

If there is only one contractor, there are changes to the duties under CDM. For the client, the contractor and any designers involved in the project. The roles that will apply to a single contractor project are:

  • The Client
  • The Contractor
  • Designers

Some roles have additional duties, and some have reduced duties. Some roles, like the principal designer and principal contractor, are removed altogether, with many of their duties passed to other members of the project team.

Clients must be made aware of CDM


On projects with only one contractor, the client no longer needs to appoint a principal contractor. Since the principal contractor is the contractor in overall control of the construction phase, because there is only one contractor, that contractor is automatically in control.

There is also no legal requirement to appoint a principal designer on projects with only one contractor.

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.

The client is responsible for providing the pre-construction information during the planning stages of the project and for notification. They are usually assisted by the principal designer, however, on single contractor projects, a principal designer may not be appointed. So the client has some extra pressure here, as they need to provide the pre-construction information without the help and support of a principal designer.

In practice, as it is a contractors duty to ensure that the client is aware of their own CDM duties, and the contractor will need this information to plan the work safely, this will often require the contractor to provide extra assistance to the client during the pre-construction phase.


For only one contractor projects, the single or sole contractor involved has to take on a few extra duties. This is because, on projects with only one contractor, the client does not need to appoint a principal designer or a principal contractor.

Now there is no principal contractor to take charge of the construction phase, this responsibility falls to the single contractor involved in the project. In theory, the coordination and cooperation on site should be more straightforward with only one contractor, working with their own team.

The single contractor has extra duties

One of the key duties of the principal contractor is to manage coordination and cooperation between contractors, and ensure they comply with their duties under CDM. As there is only one contractor involved in the project, the management of other contractors is not required.

However, certain duties would usually be carried out by the principal contractor that must now be carried out by the sole contractor on projects with only one contractor. For example, developing the construction phase plan before work starts on site.

15 - (5) If there is only one contractor working on the project, the contractor must draw up a construction phase plan, or make arrangements for a construction phase plan to be drawn up, as soon as is practicable prior to setting up a construction site.

Site inductions will also usually be provided by the principal contractor, but as there is no principal contractor on projects with only one contractor, the single contractor must provide site inductions.

Other contractor duties such as securing the site, providing welfare facilities, estimating timescales and planning stages of work will often be taken care of in part or fully by the principal contractor on larger projects with multiple contractors. On single contractor projects, the contractor must pay extra attention to these duties as it is their sole responsibility.


And what about designers? Designers duties don't change too much on projects with only one contractor. But because there is no principal designer appointed, designers should pay extra attention to their duties. There are no additional designer duties on single contractor projects. But not having a principal designer appointed can bring more work for designers, when it comes to completing their CDM responsibilities.

For example, designers need to make sure the client is aware of client duties. Usually, the principal designer will take care of this, so for projects without one, designers may need to spend extra time making sure the client is aware.

The principal designer will also usually take care of communication and sharing of information between designers and the client and contractor. Where there is no principal designer on single contractor projects, designers need to make these arrangements themselves.

Need help understanding your contractor duties under CDM? Read the free CDM duty holder guide for contractors!

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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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