CDM Regulations Explained: Client, Designer and Contractor Duties

What Are the CDM Regulations?

The Construction (Design and Management) Regulations 2015, usually just called CDM 2015, are the main legal framework for managing health, safety and welfare on construction projects in Great Britain. They apply to every construction project, from a small loft conversion to a multi-million pound new build, and they place specific duties on clients, designers and contractors rather than leaving safety entirely to whoever happens to be on site.

The thinking behind CDM is straightforward. The people who can do most to prevent harm, principally clients and designers, are often furthest removed from the actual risk. CDM 2015 makes them responsible for considering health and safety from the earliest planning stages, so decisions made on paper do not create problems that site workers then have to solve. This matters whether you are a housing association planning external refurbishment work, a school arranging building works during term time, or a contractor working on a single domestic extension.

Who Does What: The Duty Holders

CDM 2015 sets out the main duty holders, each with distinct responsibilities that cannot simply be passed to someone else:

• Client: anyone for whom a construction project is carried out, whether a commercial organisation or a private homeowner. Domestic clients are not expected to carry the full client duties; these pass to the contractor, or to the principal contractor where one is appointed. Commercial clients retain theirs in full.
• Principal Designer: appointed in writing by the client on any project involving more than one contractor. They plan, manage and monitor the pre-construction phase and coordinate health and safety matters between designers.
• Principal Contractor: also appointed in writing where there is more than one contractor. They plan, manage and monitor the construction phase itself and prepare the construction phase plan.
• Designers: anyone preparing or modifying designs, including architects, structural engineers, building services engineers and anyone specifying materials or methods that affect how the work will be built.
• Contractors: anyone who carries out, manages or controls construction work, including subcontractors and the self-employed.

On a single-contractor project, the principal designer and principal contractor roles do not arise, but the remaining duties on the client, designer and contractor still apply in full.

Client Duties in Practice

As a client you set the tone and resourcing for the whole project, and CDM 2015 gives you real legal duties, not just a passive role. In practice, a compliant client arrangement involves:

• Making suitable arrangements for managing the project, including enough time and budget for the work to be carried out safely.
• Appointing a principal designer and principal contractor in writing as soon as practicable, where there is more than one contractor.
• Providing pre-construction information, meaning everything relevant to health and safety that you already know, such as asbestos survey results, existing services drawings or site constraints.
• Ensuring welfare facilities will be in place before work starts.
• Checking that a construction phase plan exists before work begins, and that a health and safety file is prepared or updated where required.

Many clients assume that appointing a contractor discharges their duties. It does not. You remain responsible for checking that the people you appoint are competent, that arrangements are actually working, and that the project is reviewed as it progresses. For organisations managing recurring building work, such as housing associations and almshouses carrying out cyclical refurbishment, or schools and education settings running summer holiday building programmes, this often means setting up a standard CDM process that project managers follow every time, rather than reinventing it for each job.

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Designer and Contractor Duties

Designers must apply the general principles of prevention at the design stage. This does not mean eliminating every risk, which is rarely possible, but it does mean removing hazards where you reasonably can and reducing the risks you cannot remove, before passing residual risk information to those who will build, maintain and eventually demolish the structure. A designer who specifies a method of work without considering how it will actually be installed or maintained safely is not meeting this duty, however good the drawings look.

Contractors have to plan, manage and monitor their own work so that, so far as is reasonably practicable, it is carried out without risks to the health and safety of workers or anyone else affected by it, such as members of the public near a site. This includes making sure workers have the skills, knowledge, training and experience for the tasks they are given, and that they are properly supervised, particularly where young or inexperienced workers are involved. Where there is more than one contractor, the principal contractor has the added job of coordinating everyone's activities, running site inductions, securing the site against unauthorised access, and making sure contractors cooperate with each other rather than working in isolation.

Notification, Documentation and Review

A project must be notified using an F10 form if the construction work is expected to last longer than 30 working days and involve more than 20 workers at any one time, or if it will exceed 500 person-days in total. Notification is the client's duty, though the client can ask the principal designer to submit the form. Check the thresholds early rather than assuming a project falls below them, because running a notifiable project without notifying it is a straightforward compliance failure.

Two documents matter on most projects. The construction phase plan is needed on every project, while the health and safety file is required where more than one contractor is involved:

• The construction phase plan: prepared by the contractor or principal contractor before work starts, setting out how health and safety will be managed on site. It should be a live document, reviewed and updated as the project progresses and risks change, not a one-off exercise filed away on day one.
• The health and safety file: prepared by the principal designer on projects with more than one contractor, recording information that anyone carrying out future construction, maintenance or demolition work will need. It should be handed to the client at the end of the project and kept available for the life of the structure.

Records worth retaining include duty holder appointment letters, pre-construction information, the construction phase plan and its revisions, site induction and training records, and the final health and safety file. These are not just paperwork for its own sake; they are what a principal designer, an incoming contractor or an enforcing authority will ask to see if something goes wrong, or simply if the project is being audited.

Common Mistakes and Misconceptions

A common misunderstanding is that CDM only applies to large sites. It applies to all construction work, including small refurbishments, demolition, and maintenance activity that involves construction techniques, such as re-roofing or structural alterations. The duties scale with the size and complexity of the project, so a simple domestic extension needs much lighter arrangements than a multi-contractor commercial scheme, but the underlying duties do not disappear.

Other recurring problems include clients failing to appoint a principal designer in writing, treating the construction phase plan as a formality rather than a working document, and designers assuming someone else will deal with buildability and maintenance access. On manufacturing and engineering sites where construction work is carried out alongside live production, there is also a tendency to underestimate how CDM duties interact with the client's existing health and safety management system, leading to gaps in supervision and welfare provision that would not occur on a standalone construction site.

Getting Help With CDM

CDM compliance is rarely difficult once the duties are properly understood and allocated, but it does require someone to own the process from the client side.

Integral Safety provides health and safety consultancy to help clients, designers and contractors across the East Midlands understand their CDM duties, review existing arrangements, and put practical, proportionate systems in place. Where your team needs a grounding in managing health and safety risk more broadly, our IOSH Managing Safely course is a useful starting point, and our auditing and inspection service can check that site arrangements are actually working as intended. For construction businesses and clients based in the region, visit our construction sector page to see how we support projects locally, or contact us to discuss your next project.