A CDM Principal Designer is responsible for planning, managing, monitoring and coordinating health and safety during the pre-construction phase of a project. The role is required under the Construction (Design and Management) Regulations 2015 where more than one contractor is involved.

Principal Designer duties?

Planning, managing and monitoring the pre-construction phase.
Coordinating health and safety matters between designers.
Identifying foreseeable design risks and seeking to eliminate or reduce them.
Ensuring designers comply with their duties under CDM 2015.
Helping the client assemble and provide suitable pre-construction information.
Liaising with the Principal Contractor and sharing relevant design-risk information.

The Principal Designer Is Not the Project’s Technical Expert

A CDM Principal Designer is not expected to be the most knowledgeable person in every technical discipline on a project. That would be unrealistic and, on complex projects, impossible.

The Principal Designer is the designer with control over the pre-construction phase, responsible for planning, managing, monitoring and coordinating health and safety in design. Their job is to make sure the right designers are involved, information is shared, significant design risks are identified and managed, and the design team is working together effectively.

Coordination — Not Omniscience

A Principal Designer may be an architect, engineer, building surveyor or another suitably competent designer. On a multidisciplinary project, they may be coordinating structural engineers, fire engineers, process engineers, mechanical and electrical designers, temporary works designers and specialist suppliers.

They are not expected to personally reproduce every calculation, redesign every system or possess deeper specialist knowledge than the competent designer responsible for that discipline.

What they must be able to do is challenge, coordinate, identify gaps, recognise when specialist input is required, and ensure designers are addressing foreseeable risks through the design process.

Specialist Designers Still Own Their Designs

Appointing a Principal Designer does not transfer every designer’s technical responsibility to one person.

A structural engineer remains responsible for the adequacy of the structural design. A fire engineer remains responsible for their fire engineering work. A process engineer remains responsible for the process design within their scope.

The Principal Designer’s role is to make sure those designers are communicating, cooperating and managing the interfaces between their designs, particularly where one design decision creates risk elsewhere.

A Good Principal Designer Knows When to Ask the Expert

Perhaps the most important competence of a Principal Designer is not pretending to know everything.

A competent Principal Designer understands their own limits, knows which questions need to be asked, and makes sure the people with the appropriate specialist knowledge are engaged before a significant design decision is allowed to progress.

That is design risk management under CDM 2015 — not one person attempting to become the architect, structural engineer, fire engineer, process engineer and safety professional simultaneously.