The rules
CDM principal designer: when you must appoint one
Updated
Under regulation 5 of CDM 2015 you must appoint a CDM principal designer in writing whenever more than one contractor will work on the project, or it is reasonably foreseeable that more than one will, and do it before the construction phase begins.
The duty to appoint
Regulation 5(1) of the Construction (Design and Management) Regulations 2015 says that where there is more than one contractor, or it is reasonably foreseeable that more than one contractor will be working on a project, the client must appoint in writing a designer with control over the pre-construction phase as principal designer, and a contractor as principal contractor. The appointments must be made as soon as practicable and before the construction phase begins. A client that fails to appoint a principal designer must carry out the principal designer's duties itself.
Source: CDM 2015, regulation 5 (legislation.gov.uk)
Homeowners: the domestic client rule
Where the client is a domestic client, regulation 7 passes the client's duties to the contractor, or to the principal contractor where there is more than one, or to the principal designer by written agreement. If a domestic client does not make the appointments, the designer in control of the pre-construction phase becomes the principal designer by default.
Source: CDM 2015, regulation 7 (legislation.gov.uk)
The Building Regulations principal designer in England
Part 2A of the Building Regulations 2010, in force since 1 October 2023, adds a second role. Where there is more than one contractor, or it is reasonably foreseeable there will be, the client must appoint in writing a designer with control over the design work as principal designer for the Building Regulations. A client can certify in writing that the CDM principal designer is also treated as appointed to this role, so one firm can hold both.
Source: Building Regulations 2010, Part 2A (legislation.gov.uk)
Notifying HSE
Notification is a separate test. A project is notifiable to HSE if the construction work is scheduled to last longer than 30 working days and have more than 20 workers working at the same time at any point, or to exceed 500 person days. The client gives the notice before the construction phase begins.
Source: CDM 2015, regulation 6 (legislation.gov.uk)
What the principal designer does
- Plans, manages, monitors and coordinates health and safety in the pre-construction phase.
- Helps the client gather the pre-construction information and passes it to designers and contractors.
- Liaises with the principal contractor once work is on site.
- Prepares the health and safety file and hands it to the client at the end.
HSE's summary of the role.
Source: HSE: principal designers, roles and responsibilities