In short
CDM 2015 applies to all construction work in Great Britain, from a small refit to a major project. It gives specific duties to clients, designers, principal designers, contractors, principal contractors and workers. Where more than one contractor will work on a project, the client must appoint a principal designer and a principal contractor in writing.
Who does what
Client
- Who it is
- The person or organisation the project is carried out for
- Main duties
- Make suitable arrangements for managing the project; appoint a principal designer and principal contractor where needed; provide pre-construction information; make sure a construction phase plan is in place before work starts; notify HSE if the project is notifiable.
Domestic client
- Who it is
- Someone having work done on their own home, not for a business
- Main duties
- Their duties normally pass to the contractor or principal contractor, or to the principal designer by written agreement.
Principal designer
- Who it is
- A designer appointed by the client on projects with more than one contractor
- Main duties
- Plan, manage, monitor and coordinate health and safety in the pre-construction phase; help gather pre-construction information; prepare the health and safety file.
Designer
- Who it is
- Anyone who prepares or changes a design, such as architects, engineers and specifiers
- Main duties
- Eliminate, reduce or control foreseeable risks through the design, and provide information about the risks that remain.
Principal contractor
- Who it is
- A contractor appointed by the client on projects with more than one contractor
- Main duties
- Plan, manage, monitor and coordinate the construction phase; prepare the construction phase plan; provide inductions and welfare; liaise with the principal designer.
Contractor
- Who it is
- Anyone who carries out, manages or controls construction work
- Main duties
- Plan, manage and monitor their own work; make sure workers are competent and inducted; follow the principal contractor’s directions. On single-contractor projects, prepare the construction phase plan.
Workers
- Who it is
- Everyone working on the project
- Main duties
- Cooperate, report anything likely to endanger themselves or others, and take part in consultation on health, safety and welfare.
Does the project need to be notified to HSE?
A project is notifiable if the construction work on site is scheduled to either:
- last longer than 30 working days and have more than 20 workers working at the same time at any point, or
- exceed 500 person days.
Note: The client notifies HSE, using form F10, as soon as practicable before the construction phase begins.
The three key documents
- 01
Pre-construction information
Gathered by the client, with help from the principal designer, and shared with designers and contractors.
- 02
Construction phase plan
Drawn up by the principal contractor, or the contractor on single-contractor projects, before work starts.
- 03
Health and safety file
Prepared by the principal designer on projects with more than one contractor and handed to the client at the end.
Not to be confused with the Building Regulations roles
Since October 2023 the Building Regulations in England also use the titles principal designer and principal contractor, for duties about complying with the Building Regulations. One organisation can hold both roles on a project, but the duties are different and each appointment should be clear.
Sources
- HSE: CDM 2015 roles and responsibilities
- CDM 2015, regulation 6: notification
- HSE: how to notify a project (F10)
- HSE: domestic clients
Sources checked 26 September 2026 against current Health and Safety Executive guidance and legislation. This guide is general information, not legal advice; your legal duties stay with your business.