CDM 2015 Principal Contractor Duties Explained Simply

If you are the Principal Contractor on a construction project in Great Britain, you have legal duties under the Construction Design and Management Regulations 2015.

These duties are not optional. Getting them wrong can mean enforcement action, fines, and personal liability if something goes wrong.

But the regulations are written in legal language that can be hard to translate into practical action. This guide explains what Principal Contractors actually need to do in plain terms.

What is a Principal Contractor

The Principal Contractor is appointed by the Client on any construction project with more than one contractor. Their job is to plan, manage, monitor and coordinate the construction phase.

On most commercial and residential developments, the main contractor takes on the Principal Contractor role. But the role can be held by anyone with the skills, knowledge, experience and organisational capability to do it.

If you have been appointed as Principal Contractor, you need to be clear on what that means. It is not just a title. It comes with specific legal duties.

The core duty: plan, manage, monitor and coordinate

CDM 2015 Regulation 13 sets out the Principal Contractor's main duty. You must plan, manage, monitor and coordinate the construction phase.

This sounds straightforward but each word matters.

Plan means thinking ahead. Before work starts, you need to consider how it will be done safely. What are the risks? What controls are needed? How will different contractors work together without creating hazards for each other?

Manage means organising resources and people to implement the plan. This includes making sure contractors have the information they need, that site rules are clear, and that everyone knows their responsibilities.

Monitor means checking that the plan is being followed. This is not a one off activity. It means ongoing oversight throughout the construction phase. Are contractors doing what they said they would? Are controls actually in place? Are site rules being followed?

Coordinate means managing the interfaces between different contractors. Construction sites have multiple trades working in the same space. The Principal Contractor must ensure they do not create risks for each other.

You must produce a Construction Phase Plan

Before the construction phase begins, you must prepare a Construction Phase Plan. This is required by Regulation 12.

The plan must set out the arrangements for managing the significant health and safety risks associated with the project. It must be appropriate to the scale and complexity of the work.

There is no fixed format. The HSE does not provide a template that you must follow. What matters is that the plan addresses the actual risks of your specific project.

For a simple project, the Construction Phase Plan might be a few pages. For a complex project, it could be much longer. The test is whether it genuinely helps manage the work safely, not whether it ticks boxes.

Key things the Construction Phase Plan should cover include:

A description of the project and the arrangements for managing it. Who is who, what communication channels exist, how decisions get made.
The health and safety risks and how they will be managed. This does not mean listing every possible hazard. It means identifying the significant risks of this project and explaining the approach to controlling them.
Arrangements for controlling high risk activities. Work at height, excavations, demolition, confined spaces, and other activities with serious injury potential need specific attention.
How the site will be organised. Access, traffic routes, welfare facilities, emergency procedures.

The plan is not a static document. It should be reviewed and updated as the project progresses and circumstances change.

Site rules and ensuring they are followed

As Principal Contractor, you must draw up site rules where necessary. These rules must be appropriate to the site and the activities taking place.

Common site rules cover things like:

Personal protective equipment requirements. What PPE is mandatory on site and in which areas.
Traffic management. How vehicles and pedestrians move around the site safely.
Permit to work requirements. Which activities need formal permits before they can start.
Housekeeping standards. Expectations for keeping work areas tidy and access routes clear.

But having rules is not enough. You must also take reasonable steps to ensure the rules are followed. This means communicating them clearly, checking compliance, and taking action when rules are broken.

If contractors repeatedly ignore site rules and you do nothing about it, you are not meeting your duty. Monitoring means actually monitoring, not just hoping for the best.

Contractor competence and information

You must satisfy yourself that contractors you engage have the skills, knowledge, experience and organisational capability to carry out their work safely.

This does not mean collecting certificates and assuming everything is fine. It means making a genuine assessment based on the nature of the work they will be doing.

For specialist high risk work, you need to be more rigorous than for straightforward tasks. What has this contractor done before? Do they understand the specific risks? Do they have adequate supervision and management?

You must also provide contractors with the information they need to do their work safely. This includes relevant parts of the Construction Phase Plan and any information about site conditions or hazards that could affect their work.

Information must flow in both directions. You must ensure that contractors share information that could affect the health and safety of others on site.

Consulting and engaging workers

CDM 2015 requires you to consult and engage with workers on health and safety matters. This is not just about having a suggestion box.

Workers should be involved in identifying hazards and developing solutions. They often know more about the practical risks of their tasks than anyone else. Ignoring this knowledge wastes a valuable safety resource.

Engagement also builds commitment. When workers feel involved in safety decisions, they are more likely to follow the rules and speak up when something is wrong.

This duty applies to all workers, not just your direct employees. If subcontractors have workers on your site, you need to ensure they are consulted and engaged too.

Maintaining the site safely

You have duties around the physical conditions of the site. This includes providing adequate welfare facilities, ensuring safe access and egress, and maintaining good order and housekeeping.

Welfare facilities must be available from the start of the construction phase. This means toilets, washing facilities, drinking water, changing rooms, and somewhere to rest and eat. These facilities must be maintained throughout the project.

Access routes must be kept safe. This means managing traffic, maintaining scaffolding and ladders, and ensuring people can move around the site without unnecessary risk.

Good housekeeping matters more than many people realise. Trips and falls are among the most common construction injuries. Keeping work areas tidy and access routes clear is basic but essential.

What about the Client and Principal Designer

The Principal Contractor does not work in isolation. CDM 2015 creates a framework where the Client, Principal Designer and Principal Contractor each have duties that complement each other.

The Client must make suitable arrangements for managing the project and ensure adequate time and resources are allocated for safety. They provide pre construction information about the site.

The Principal Designer leads on health and safety in the pre construction phase. They identify, eliminate and control foreseeable risks through design. They prepare the health and safety file.

As Principal Contractor, you must cooperate with both. You need to liaise with the Principal Designer on ongoing design work. You need to help the Client meet their duties. You need to contribute to the health and safety file with information relevant to future maintenance and operation.

Proving you have met your duties

If an incident occurs, the HSE will want to see evidence that you were meeting your duties as Principal Contractor. They will not accept verbal assurances.

This means keeping records. Not paperwork for the sake of paperwork, but genuine evidence that you were planning, managing, monitoring and coordinating the construction phase.

Useful records include:

The Construction Phase Plan and any updates to it. This shows you were planning ahead.
Records of site inductions and briefings. This shows you were communicating information to workers.
Inspection records and audit reports. This shows you were monitoring conditions and compliance.
Evidence of action taken when problems were found. This shows monitoring was leading to improvement, not just box ticking.
Minutes from progress meetings where safety was discussed. This shows coordination was happening.
Daily Safe Work Plans that document what work was happening, what hazards were identified, and what controls were in place. This shows safety management was happening at a practical level, every day.

The best evidence is systematic. If you have a clear process that generates records automatically, you will be in a strong position if you ever need to demonstrate compliance.

Summary

As Principal Contractor under CDM 2015, your duty is to plan, manage, monitor and coordinate the construction phase.

This means producing a Construction Phase Plan, establishing and enforcing site rules, checking contractor competence, engaging workers, and maintaining safe site conditions.

Documentation matters. If you cannot prove you were doing these things, it is very hard to show you were meeting your duties.

The regulations might be written in legal language but the practical requirements are straightforward. Know what is happening on your site. Make sure risks are controlled. Check that controls are working. Keep records that demonstrate you were doing all of this.

Need help meeting your Principal Contractor duties? See how SimpleSafeWork can help.