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Part of our CDM 2015 series. See CDM Regulations 2015 explained for every duty holder and key document in one place.
The principal contractor is the contractor appointed by the client to plan, manage, monitor and coordinate health and safety during the construction phase of a project with more than one contractor. In practice, the site manager is usually the person who carries out those duties day to day.
When a principal contractor must be appointed
Under CDM 2015 regulation 5, the client must appoint a principal contractor in writing where there is, or is likely to be, more than one contractor working on the project. The appointment should be made as early as possible, before the construction phase starts.
- If the client does not appoint one, the client must carry out the principal contractor’s duties itself (regulation 5(4)).
- Domestic clients do not have to appoint anyone. The principal contractor role passes to the contractor in control of the construction phase, or the client’s duties pass to the contractors (regulation 7).
- Competence matters. Anyone appointed must have the skills, knowledge, experience and organisational capability to do the job (regulation 8).
The main duties at a glance
| Duty | What it means on site | CDM 2015 |
|---|---|---|
| Plan, manage and monitor the construction phase | Organise the work so it is carried out without risks to health and safety, so far as is reasonably practicable. | Regulation 13(1) |
| Apply the general principles of prevention | Take account of them when making design, technical and organisational decisions, and when estimating how long work will take. | Regulation 13(2) |
| Coordinate contractors | Organise cooperation between contractors, including sequencing of work and shared risks. | Regulation 13(3) |
| Ensure a suitable site induction | Every worker gets a site induction before starting. | Regulation 13(4) |
| Prevent unauthorised access | Secure the site boundary and control who enters. | Regulation 13(4) |
| Provide welfare facilities | Toilets, washing, drinking water, rest and changing facilities to Schedule 2, from the start and throughout. | Regulation 13(4) and Schedule 2 |
| Liaise with the principal designer | Share information that affects design and the health and safety file. | Regulation 13(5) |
| Draw up and maintain the construction phase plan | Before setting up the site, and keep it up to date. | Regulation 12 |
| Consult and engage with workers | Make sure workers can raise concerns and are involved in decisions that affect them. | Regulation 14 |
| Contribute to the health and safety file | Provide information for the file, and take over the file if the principal designer’s appointment ends first. | Regulation 12 |
The construction phase plan is the document that ties most of these duties together.
What principal contractor duties look like day to day
- Checking contractor RAMS before work starts, and checking they are followed
- Running inductions and keeping a record of who is on site
- Holding coordination meetings and planning the sequence of trades
- Managing traffic routes, deliveries, storage and access
- Inspecting scaffolds, excavations and temporary works arrangements
- Making sure welfare is clean, stocked and adequate for the number of workers
- Reviewing accidents and near misses, and reporting under RIDDOR where required
Notifying HSE
Notifying HSE of a project is the client’s duty, not the principal contractor’s, but the principal contractor must display a copy of the notification on site where workers can see it. A project is notifiable if it will last more than 30 working days with more than 20 workers at the same time at any point, or will exceed 500 person days.
CDM principal contractor or Building Regulations principal contractor?
Since 1 October 2023, the Building Regulations in England also use the term principal contractor, introduced alongside the Building Safety Act 2022. That role is about compliance with building regulations, such as fire safety and structural requirements. The CDM role is about health and safety during construction. The same organisation is often appointed to both, but they are separate duties and should be appointed separately.
Common gaps
- No written appointment from the client
- A construction phase plan written once and never reviewed
- Contractor RAMS accepted without being read
- Inductions that cover site rules but not the actual risks
- Welfare that falls behind as the workforce grows
- No clear system for workers to raise concerns
Training that helps
SMSTS is the course most principal contractors ask their site managers to hold. For a recognised management qualification, the NEBOSH Health and Safety Management for Construction certificate covers CDM duty holders in detail. Our managing contractors eLearning and CDM awareness eLearning are quick online options for wider teams.
Where this fits in SMSTS and SSSTS
The duties of the principal contractor, and how site managers carry them out, are a central part of SMSTS. Our free SMSTS mock test and SSSTS mock test let you check your knowledge before the course or a refresher, and you can email yourself the results sheet at the end.
When you are ready, the five day SMSTS course is for site managers and the two day SSSTS course is for supervisors. If your certificate is due, the SMSTS refresher and SSSTS refresher keep it current.
Frequently asked questions
Who appoints the principal contractor?
The client, in writing, on any project with more than one contractor. If the client does not appoint one, the client takes on the duties itself.
Can the principal contractor also be the principal designer?
Yes, on a design and build project one organisation can hold both roles, provided it has the competence for each.
Does a domestic project need a principal contractor?
If more than one contractor is involved, yes. The domestic client does not have to make the appointment; the role passes automatically to the contractor in control of the construction phase.
Is the site manager the principal contractor?
No. The principal contractor is the organisation. The site manager is usually the person who carries out its duties on site.
Read the source
The Construction (Design and Management) Regulations 2015, regulations 5 to 8 and 12 to 15 and Schedule 2; HSE guidance L153, Managing health and safety in construction; and HSE information on the Building Regulations dutyholder roles introduced from 1 October 2023 under the Building Safety Act 2022. Facts checked on 6 October 2026.
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