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Part of our CDM 2015 series. See CDM Regulations 2015 explained for every duty holder and key document in one place.
The principal designer is the designer appointed by the client to plan, manage, monitor and coordinate health and safety in the pre-construction phase of a project with more than one contractor. It is the role that makes sure design risks are dealt with before anyone sets foot on site.
When a principal designer must be appointed
The client must appoint a principal designer in writing wherever there is, or is likely to be, more than one contractor on the project. The appointment should be made as early as possible, ideally at the concept stage, so the principal designer can influence the design. If the client does not appoint one, the client must carry out the duties itself.
Who can be the principal designer?
The principal designer must be a designer with control over the pre-construction phase. It can be an organisation or an individual, such as an architect, engineer, design and build contractor or specialist consultant. What matters is that they have the skills, knowledge, experience and organisational capability for the size and complexity of the project, and genuine influence over the design.
Every principal designer duty at a glance
| Duty | What it means in practice |
|---|---|
| Plan, manage, monitor and coordinate the pre-construction phase | Make sure the project is designed so it can be built, used and maintained without risks to health and safety, so far as is reasonably practicable. |
| Identify and eliminate or control foreseeable risks | Through design, during construction, maintenance, cleaning and use of the building as a workplace. |
| Make sure designers comply with their duties | Check that each designer is eliminating, reducing or controlling risks and passing on information. |
| Make sure everyone cooperates | Coordinate designers, the client and the principal contractor so information flows. |
| Help the client with pre-construction information | Assist the client to gather pre-construction information and pass it to designers and contractors. |
| Liaise with the principal contractor | Share information that affects the construction phase plan and the work on site. |
| Prepare the health and safety file | Build the health and safety file during the project, review and update it, and pass it on at the end. |
Does the role end when work starts on site?
No. Design work often continues during construction, and the principal designer keeps coordinating it. The principal designer also continues to build the health and safety file. If the principal designer’s appointment ends before the project finishes, they must pass the file to the principal contractor.
CDM principal designer or Building Regulations principal designer?
| CDM 2015 principal designer | Building Regulations principal designer | |
|---|---|---|
| Purpose | Health and safety during construction and in future use and maintenance | Compliance of the design with the building regulations |
| Where | Great Britain | England, from 1 October 2023 |
| Appointed by | The client, where there is more than one contractor | The client, where there is more than one contractor |
| Main focus | Design risk, pre-construction information, the health and safety file | Planning, managing and monitoring design work so it complies with building regulations |
The titles match, but the duties are separate and supplementary. One organisation can hold both roles if it is competent for each, and many clients appoint the same firm, but each appointment should be made clearly in writing.
Principal designer or principal contractor?
The principal designer leads on health and safety before construction and on design throughout. The principal contractor leads during the construction phase on site. The two must work closely together, especially on the construction phase plan and the health and safety file.
Common gaps
- Appointed too late to influence the design
- Appointed in name only, with no real control over designers
- Pre-construction information not gathered or not passed on
- Design risk registers full of generic hazards rather than project-specific decisions
- A health and safety file left until the last week of the project
Training that helps
Principal designers need a strong grasp of CDM and construction risk. The NEBOSH Health and Safety Management for Construction certificate covers CDM duty holders and design risk management, and NEBOSH Managing Risks covers risk assessment and controls. Our CDM awareness eLearning is a quick introduction for design teams.
Where this fits in SMSTS and SSSTS
The principal designer’s role and how it links with the site team are part of the CDM topics on SMSTS and SSSTS. Our free SMSTS mock test and SSSTS mock test let you check your knowledge before the course or a refresher, and you can email yourself the results sheet at the end.
When you are ready, the five day SMSTS course is for site managers and the two day SSSTS course is for supervisors. If your certificate is due, the SMSTS refresher and SSSTS refresher keep it current.
Frequently asked questions
Who appoints the principal designer?
The client, in writing, on any project with more than one contractor.
Can a contractor be the principal designer?
Yes, on a design and build project a contractor with design control can be appointed as principal designer, provided it is competent for the role.
Is the CDM principal designer the same as the Building Regulations principal designer?
No. They share a title but have separate duties. The same organisation can be appointed to both if it is competent for each.
Who prepares the health and safety file?
The principal designer, during the project. If their appointment ends early, the file passes to the principal contractor, who hands it to the client at the end.
Read the source
The Construction (Design and Management) Regulations 2015, regulations 5, 8, 11 and 12; HSE guidance L153, Managing health and safety in construction; the Building Regulations 2010, Part 2A, as inserted by the Building Regulations etc. (Amendment) (England) Regulations 2023; and CIBSE guidance on the dutyholder and competence regulations. Facts checked on 6 October 2026.
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