The CDM Principal Contractor is a duty holder created by the Construction (Design and Management) Regulations 2015 (CDM 2015). On notifiable projects - those lasting more than 30 working days with more than 20 workers on site simultaneously, or exceeding 500 person-days in total - the client must appoint a Principal Contractor in writing before construction begins. The Principal Contractor is responsible for planning, managing, monitoring and coordinating all health and safety during the construction phase. They must prepare and maintain a Construction Phase Plan, ensure all contractors receive the site rules and pre-construction information, and manage the overall health and safety of everyone on site. The role is carried out by the main contractor on most projects - it is a legal function rather than a separate professional appointment.
What they do (CDM duties)
- Prepare and update the Construction Phase Plan before construction begins
- Plan, manage and monitor construction phase health and safety
- Coordinate health and safety across all contractors and subcontractors
- Ensure site welfare facilities meet the requirements of Schedule 2 to CDM 2015
- Liaise with the Principal Designer on pre-construction information
- Notify the HSE using the F10 form for notifiable projects
- Manage site inductions and ensure all workers are briefed on site rules
- Contribute to and maintain the Health and Safety File
When a Principal Contractor must be appointed
The legal threshold for a notifiable project - and therefore a mandatory Principal Contractor appointment - is set out in CDM 2015. The client must make the appointment in writing before the construction phase begins.
CDM 2015 duty holders at a glance
| Duty holder | Who they are / their role |
|---|---|
| Client | The organisation or individual for whom the work is carried out; ultimate CDM responsibility |
| Principal Designer | Appointed by client on notifiable projects; coordinates H&S in pre-construction phase |
| Principal Contractor | Appointed by client on notifiable projects; manages H&S during construction phase |
| Designer | Anyone who prepares or modifies construction drawings or specifications |
| Contractor | Any individual or company carrying out construction work |
On projects with only one contractor, that contractor carries out both the Principal Contractor and Contractor duties. The Principal Contractor role is a legal function, not a separate fee-earning appointment - it is carried out by the main contractor as part of their contract.
Qualifications and competence
CDM 2015 does not specify a particular qualification for Principal Contractors. Competence is assessed on the basis of skills, knowledge, experience and organisational capability relevant to the project. The HSE provides guidance on assessing contractor CDM competence in its pre-qualification guidance (PAS 91 and equivalent).
Site managers and supervisors on notifiable projects should hold Site Management Safety Training Scheme (SMSTS) or Site Supervisor Safety Training Scheme (SSSTS) certification as a minimum. These CITB-accredited courses cover CDM duties and site health and safety management.
Many public sector and framework clients require contractors to hold third-party health and safety pre-qualification accreditation (CHAS, Constructionline Gold, SafeContractor) as evidence of CDM competence. These schemes assess a contractor's health and safety management systems and documentation.
HSE CDM guidance
Frequently asked questions
When must a Principal Contractor be appointed under CDM 2015?
A Principal Contractor must be appointed whenever a project is notifiable to the HSE - that is, when it will last longer than 30 working days with more than 20 workers simultaneously on site, or when it will exceed 500 person-days in total. Once a project meets either of these thresholds, the client must appoint a Principal Contractor in writing before the construction phase begins. On a notifiable project, the client must also appoint a Principal Designer to coordinate health and safety during the pre-construction phase.
What is a Construction Phase Plan and who prepares it?
The Construction Phase Plan (CPP) is a document prepared by the Principal Contractor before construction begins on any notifiable project. It sets out how health and safety will be managed throughout the construction phase - covering site rules, welfare arrangements, emergency procedures, and how specific risks identified in the pre-construction information will be managed. On smaller projects the CPP can be brief and proportionate to the risk. On larger or more complex sites it is a comprehensive living document updated throughout the project.
Does a domestic extension need a CDM Principal Contractor?
Most domestic extensions do not trigger the CDM notification threshold and therefore do not require a formally appointed Principal Contractor. However, CDM 2015 still applies to all construction work including domestic projects - all contractors have CDM duties even on small sites. Where a domestic project does exceed the threshold (for example a very large new build with numerous trades over an extended programme), a Principal Contractor must be appointed. In practice, the main contractor normally takes on the Principal Contractor role on notifiable domestic projects.