What Is a Principal Designer?

Short answer: a Principal Designer is the designer appointed by the client to plan, manage and coordinate the design phase of a construction project. Since 2023 there are two such roles in England: one under the CDM Regulations 2015 (health and safety) and one under the Building Regulations (compliance). They can be held by the same competent person or firm.

Book a free 30-minute consultation

The CDM Principal Designer

Under CDM 2015, a Principal Designer is required where more than one contractor will work on a project. Their duties include:

• planning, managing and monitoring the pre-construction phase so health and safety risks are eliminated or controlled through design
• coordinating health and safety matters between designers
• helping the client prepare and share pre-construction information
• liaising with the Principal Contractor
• preparing, reviewing and handing over the health and safety file

The Building Regulations Principal Designer

Introduced through the Building Safety Act 2022 and in force from October 2023, this role applies where more than one designer is involved. The Building Regulations Principal Designer must plan, manage and monitor design work so that, if built, it complies with all relevant requirements of the Building Regulations. They coordinate designers, communicate with the Principal Contractor and provide a compliance statement at completion. On higher-risk buildings, their work underpins the Gateway 2 and Gateway 3 applications.

Principal Designer duties at a glance

Duty	CDM PD	Building Regs PD
Plan and manage the design phase	✓ (health and safety)	✓ (compliance)
Coordinate other designers	✓	✓
Pre-construction information	✓	n/a
Health and safety file	✓	n/a
Compliance statement at completion	n/a	✓

Who can be a Principal Designer?

Any designer, whether an organisation or an individual, with the skills, knowledge, experience and, for organisations, organisational capability to carry out the role. It is often the architect or lead designer. On design-and-build projects, the contractor may take the role if they control the design. The client must take reasonable steps to check competence before appointing.

What if no Principal Designer is appointed?

If the client fails to appoint one, the client takes on the duties themselves. For domestic clients, the duties normally pass to the designer in control of the pre-construction phase.

Need a Principal Designer? See our Principal Designer services.

When do you need a Principal Designer? A quick checklist

• More than one contractor will work on the project: a CDM Principal Designer is required.
• More than one designer is involved (for example architect, structural engineer and M&E designer): a Building Regulations Principal Designer is required.
• The building is higher-risk (18 metres or seven storeys with two or more homes): the Principal Designer’s work feeds directly into the Gateway 2 application.
• You are a domestic client: the roles still apply, but your duties normally pass to the designer or contractor.

CDM Principal Designer vs Building Regulations Principal Designer

The two roles share a name but answer different questions. The CDM Principal Designer asks “can this be built, used and maintained safely?”. The Building Regulations Principal Designer asks “if it is built as designed, will it comply?”. Appointing one competent firm to hold both roles usually avoids gaps between health and safety and compliance, and keeps a single point of responsibility for the design team.

Ready to appoint? See our Principal Designer services, or read how we prepare building regulations drawings.

Frequently asked questions

Do I need a Principal Designer for an extension or loft conversion?

Often yes. If more than one contractor or more than one designer is involved, the Principal Designer roles apply even on domestic projects, although the homeowner’s duties normally transfer to the designer or contractor.

Is a Principal Designer required under the Building Safety Act?

The Building Safety Act 2022 introduced the Building Regulations Principal Designer role through the dutyholder regime that came into force in October 2023. It applies where more than one designer works on a project.

What is the role of a Principal Designer?

To plan, manage, monitor and coordinate the design phase of a project: under CDM 2015 for health and safety, and under the Building Regulations for compliance.

Is the Principal Designer the same as the architect?

Not necessarily. The architect is often appointed as Principal Designer, but the roles are separate and must be appointed in writing.

Can the principal contractor be the principal designer?

Under CDM 2015 it is possible on some projects, typically design-and-build, if the contractor is a designer with control over the design and is competent.

Do domestic projects need a Principal Designer?

Yes, where there is more than one contractor (CDM) or more than one designer (Building Regulations). The domestic client's duties usually transfer to the contractor or designer.

Lucia Piccinini is the founder of LP ARKinnovation, a RIBA Chartered Practice working across London and beyond, including Chiswick, Hammersmith, Fulham, Chelsea, Kensington, Westminster, Tower Hill, Islington, Brentford, Hounslow, Richmond, Windsor and Maidenhead. ARB registered architect (085370D), RIBA Chartered Member and registered with the Ordine degli Architetti in Italy, with more than 15 years of practice across London, Florence and Milan. She writes a monthly column for Property Investor News, contributes to Fairness Magazine and speaks at property industry events. Press, articles and podcasts.