Is my architect the CDM principal designer?

Only if they have been appointed in writing, or if it is a domestic project where nobody has been appointed and they are the designer in control of the pre-construction phase. It is not automatic on a commercial project.

Can one person be principal designer and principal contractor?

They are separate appointments with separate duties and are normally held by different organisations, because one is a designer role and the other a contractor role. A design and build contractor with in-house design can hold both, but the duties still have to be discharged separately.

Principal designer

What is a CDM principal designer?

Short answer

A CDM principal designer is the designer a client appoints, in writing, to plan, manage and monitor health and safety through the pre-construction phase of a building project, and to coordinate the designers so that the risks their designs create are dealt with before anyone is on site. The role is created by regulation 5 of the Construction (Design and Management) Regulations 2015, and the duties are in regulations 11 and 12. It is required on any project involving more than one contractor, including domestic ones.

The rule

Regulation 5(1) of CDM 2015: where there is more than one contractor, or if it is reasonably foreseeable that more than one contractor will be working on a project at any time, the client must appoint in writing a designer with control over the pre-construction phase as principal designer, and a contractor as principal contractor.

Note what the role is not. It is not a health and safety inspector, and it is not a job about the site. The regulations tie it to the pre-construction phase: the period when the project is being designed and planned, before and up to the point where construction begins, and afterwards for as long as design work continues.

What the duties actually are

Regulation 11 sets out five things the principal designer must do. Stated plainly:

Plan, manage and monitor the pre-construction phase
and coordinate health and safety matters through it, so the work can be carried out without risks to health or safety so far as is reasonably practicable.
Identify, eliminate or control foreseeable risks
to anyone carrying out or affected by the construction work, anyone maintaining or cleaning the structure afterwards, and anyone who will use the structure as a workplace.
Make sure every designer is doing their job
Regulation 11(4) requires the principal designer to ensure all designers comply with their own duties in regulation 9.
Get the information out
Assist the client in providing the pre-construction information, and provide it promptly and in a convenient form to every designer and contractor who needs it.
Liaise with the principal contractor
For the duration of the appointment, sharing what is relevant to planning, managing and monitoring the construction phase.

Regulation 12(5) adds the sixth: prepare a health and safety file appropriate to the characteristics of the project.

The five CDM 2015 dutyholders, drawn as the information actually moves. The client appoints a principal designer and a principal contractor in writing before the construction phase begins. Each designer passes up the risks their design leaves behind, under regulation 9(3). The principal designer gathers that with the client's own information and hands it to the principal contractor for the construction phase plan, under regulation 12(3). The principal contractor passes down the parts of that plan each contractor needs.

Who can be one

HSE describes a principal designer as a designer, an organisation or on smaller projects an individual, appointed by the client. The critical word is designer: the role must be held by someone with control over the pre-construction phase, not by a bystander.

It can be your architect or architectural designer, if they are appointed in writing and set up to do it. It can be a specialist appointed alongside them. It can be the client themselves on a commercial project, though regulation 5(3) means that is what happens by default rather than by design: if the client fails to appoint a principal designer, the client must carry out the principal designer's duties in regulations 11 and 12.

How it is different from the Building Regulations principal designer

Since 1 October 2023 there has been a second principal designer role in England, created by Part 2A of the Building Regulations 2010. It has a similar name and a completely different job: designing to meet the Building Regulations, rather than health and safety in construction. A project can need both, and one appointment does not make the other.

The full comparison.

What this means for you

If you are the client: the appointment is yours to make, in writing, before the construction phase begins. It does not happen automatically because your architect is involved.

If you are the designer: on a domestic project where the client appoints nobody, regulation 7(2) makes the designer in control of the pre-construction phase the principal designer, whether or not that was ever discussed. More on that.

If you are the contractor: the principal designer is where the pre-construction information should be coming from, and under regulation 12(3) the information you build the construction phase plan on.

Written by Robbie Thompson, BA (Hons) Dip Arch, SMSTSLast reviewed 28 August 2026How we write this

Sources

CDM 2015, regulation 5: appointment of the principal designer and the principal contractor legislation.gov.uk
CDM 2015, regulation 11: duties of a principal designer legislation.gov.uk
CDM 2015, regulation 12: construction phase plan and health and safety file legislation.gov.uk
HSE: principal designers, roles and responsibilities hse.gov.uk
Managing health and safety in construction, L153 HSE guidance on the Regulations

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