Principal Designer vs Principal Contractor: what is the difference?

The roles are closely connected, but they are not interchangeable. Each has a different area of control, different legal duties and different responsibilities for coordinating the people involved in the project. HSE summary of CDM 2015 duties: side-by-side summary of the duty holders and the domestic-client arrangements (opens in a new tab)

What is a Principal Designer under CDM 2015?

A Principal Designer is a designer appointed by the client to take control of the pre-construction phase on a project involving more than one contractor. HSE guidance for principal designers: principal designers: roles and responsibilities under CDM 2015 (opens in a new tab)

The role focuses on planning, managing, monitoring and coordinating health and safety while design and pre-construction work is being carried out. The Principal Designer must also work with other designers to eliminate foreseeable risks where possible and reduce or control risks that cannot reasonably be eliminated. Read Regulation 11 on legislation.gov.uk: duties of a principal designer in relation to health and safety at the pre-construction phase (opens in a new tab)

The Principal Designer duties guide sets out each of those duties in full.

What is a Principal Contractor under CDM 2015?

A Principal Contractor is a contractor appointed by the client to take control of the construction phase on a project involving more than one contractor. HSE guidance for principal contractors: principal contractors: roles and responsibilities under CDM 2015 (opens in a new tab)

The role focuses on planning, managing, monitoring and coordinating health and safety while construction work is being carried out. This includes coordinating contractors, preparing and maintaining the construction phase plan, providing site inductions, preventing unauthorised access, providing welfare and consulting workers. Read Regulation 13 on legislation.gov.uk: duties of a principal contractor in relation to health and safety at the construction phase (opens in a new tab)

The Principal Contractor duties guide sets out each of those duties in full.

Principal Designer vs Principal Contractor at a glance

When are both roles required?

The client must appoint both a Principal Designer and a Principal Contractor where there is more than one contractor, or where it is reasonably foreseeable that more than one contractor will be working on the project at any time. Read Regulation 5 on legislation.gov.uk: appointment of the principal designer and the principal contractor, and the client fallback (opens in a new tab)

The appointments must be made in writing as soon as practicable and, in any event, before the construction phase begins. Read Regulation 5 on legislation.gov.uk: appointment of the principal designer and the principal contractor, and the client fallback (opens in a new tab)

The trigger is the number of contractors, not the size, value or duration of the project, and not whether it is notifiable. The duty holders guide explains how that test works in practice.

Who appoints the Principal Designer and Principal Contractor?

For a commercial project, the client makes both appointments. The client must also take reasonable steps to ensure the people or organisations appointed have the skills, knowledge and experience, and where relevant the organisational capability, needed to fulfil their roles in a way that secures health and safety. HSE L153 guidance: Managing health and safety in construction, appointments, capability and coordination, PDF (opens in a new tab)

Domestic-client projects have special arrangements under Regulation 7. The roles are still required on a multi-contractor project, but domestic-client duties normally transfer to other duty holders. Read Regulation 7 on legislation.gov.uk: application to domestic clients, including transferred duties and the fallback appointments (opens in a new tab)

What are the Principal Designer’s main duties?

• Plan, manage, monitor and coordinate health and safety during the pre-construction phase.
• Identify, eliminate or control foreseeable health and safety risks through design.
• Ensure designers comply with their CDM duties.
• Assist the client with identifying, obtaining and providing relevant pre-construction information.
• Coordinate cooperation and communication between designers and others involved in pre-construction work.
• Liaise with the Principal Contractor and provide information about risks that need to be managed during construction.
• Prepare, review and update the health and safety file on projects where one is required.

Each of these is explained in detail in the Principal Designer duties guide. Read Regulation 11 on legislation.gov.uk: duties of a principal designer in relation to health and safety at the pre-construction phase (opens in a new tab)

What are the Principal Contractor’s main duties?

• Plan, manage, monitor and coordinate health and safety during the construction phase.
• Prepare the construction phase plan before construction begins and keep it under review.
• Coordinate contractors and organise cooperation between them.
• Provide suitable site inductions and relevant health and safety information.
• Take reasonable steps to prevent unauthorised access to the construction site.
• Provide and maintain suitable welfare facilities.
• Consult and engage workers on matters affecting their health, safety and welfare.
• Liaise with the client and Principal Designer and take account of relevant design and pre-construction information.

Each of these is explained in detail in the Principal Contractor duties guide. Read Regulation 13 on legislation.gov.uk: duties of a principal contractor in relation to health and safety at the construction phase (opens in a new tab)

How do the Principal Designer and Principal Contractor work together?

The interface between the two roles is critical. Design and construction phases can overlap, so information cannot simply be handed over once and forgotten.

The Principal Designer should keep the Principal Contractor informed about design risks and relevant pre-construction information. The Principal Contractor should provide information back where construction methods, sequencing or site conditions create issues that may affect design or future work.

Both roles should cooperate with the client and with each other so that risks are managed consistently as the project moves from design into construction. HSE summary of CDM 2015 duties: side-by-side summary of the duty holders and the domestic-client arrangements (opens in a new tab)

Can the same organisation be Principal Designer and Principal Contractor?

CDM 2015 does not prevent the same organisation from carrying out both roles, provided it genuinely meets the requirements for each role and can fulfil both sets of duties. HSE L153 guidance: Managing health and safety in construction, appointments, capability and coordination, PDF (opens in a new tab)

The organisation must still be a designer for the Principal Designer role and a contractor for the Principal Contractor role, with appropriate control of the relevant project phases. Holding both titles does not merge or reduce the legal duties.

Can an individual be Principal Designer or Principal Contractor?

Yes. Depending on the project, either role can be carried out by an individual or an organisation, provided the person or organisation is capable of fulfilling the role and has the relevant control of the phase concerned. HSE summary of CDM 2015 duties: side-by-side summary of the duty holders and the domestic-client arrangements (opens in a new tab)

On larger or more complex projects, the functions will often be delivered by a wider team even though the appointment is made to a particular individual or organisation.

What happens if the client does not make the appointments?

On a commercial project, if the client fails to appoint a Principal Designer, the client must fulfil the Principal Designer duties. If the client fails to appoint a Principal Contractor, the client must fulfil the Principal Contractor duties. Read Regulation 5 on legislation.gov.uk: appointment of the principal designer and the principal contractor, and the client fallback (opens in a new tab)

Different fallback arrangements apply to domestic clients. Where a domestic client does not make the required appointments, the designer in control of the pre-construction phase becomes the Principal Designer and the contractor in control of the construction phase becomes the Principal Contractor. Read Regulation 7 on legislation.gov.uk: application to domestic clients, including transferred duties and the fallback appointments (opens in a new tab)

Are the CDM roles the same as the Building Regulations Principal Designer and Principal Contractor?

No. In England, Principal Designer and Principal Contractor roles also exist under the Building Regulations duty-holder regime. The titles are similar, but the legal duties and purposes are different.

A project may appoint the same person or organisation to corresponding roles where the relevant requirements are satisfied, but an appointment under CDM 2015 should not be treated as automatically proving that the Building Regulations role has also been correctly appointed or fulfilled. The role guides cover this for the Principal Designer and the Principal Contractor.

Principal Designer and Principal Contractor checklist

For a project involving more than one contractor, check that:

• The client has identified that Principal Designer and Principal Contractor appointments are required.
• Both appointments are made in writing.
• The appointments are made as soon as practicable and before the construction phase begins.
• The Principal Designer is a designer with control of the pre-construction phase.
• The Principal Contractor is a contractor with control of the construction phase.
• The client has taken reasonable steps to assess capability for each appointment.
• Pre-construction information is provided and kept relevant.
• The Principal Designer and Principal Contractor have clear arrangements for cooperation and information exchange.
• The construction phase plan is prepared before construction starts.
• The health and safety file is being developed where required.
• Any overlapping design and construction work is actively coordinated rather than treated as a one-off handover.

Common Principal Designer vs Principal Contractor mistakes

Treating the roles as interchangeable

They control different phases and have different statutory duties.

Appointing a project manager by title alone

A job title does not itself make someone a suitable Principal Designer or Principal Contractor.

Making the appointments too late

The appointments should be made as soon as practicable and before construction begins.

Assuming the Principal Designer stops being relevant once site work starts

Design work and construction often overlap, so liaison may continue throughout the project.

Assuming the Principal Contractor owns design risk

The Principal Contractor manages the construction phase, but designers and the Principal Designer retain their own design-related duties.

Confusing CDM roles with Building Regulations roles

The titles may be the same in England, but the statutory regimes and duties are different.