Principal Designer Duties for Domestic Projects

What Principal Designer means

Confusingly, two separate regimes use the term “Principal Designer”, and they are not the same. One arises under the Construction (Design and Management) Regulations 2015 (CDM) and concerns health and safety during the design phase. The other arises under the Building Regulations and concerns design-stage compliance with those regulations. A project may engage one, both or neither, depending on its nature.

Domestic client context

For domestic clients — homeowners having work done on their own home — duties under CDM are often reduced and can pass to the contractor or principal contractor by default. The responsibilities do not vanish, however; they need to be clearly allocated. Understanding who holds which duty avoids gaps that can affect safety, compliance and accountability.

Building Regulations Principal Designer

The Building Regulations Principal Designer duty addresses the coordination of design work so that, when complete, the building work would be compliant with the building regulations. It applies where there is more than one designer, and it focuses on compliance rather than site safety. It is a design-stage coordination role, distinct from building control’s separate function of checking and approving the work.

CDM Principal Designer

The CDM Principal Designer coordinates health and safety during the pre-construction (design) phase where a project involves more than one contractor. The role includes planning, managing and monitoring design-stage health and safety, and ensuring relevant information is provided to those who need it. It is appointed in writing by the client where it applies.

When written appointments matter

Both roles benefit from — and in some cases require — a clear written appointment defining who holds the duty, the scope, and the terms. A written appointment removes ambiguity about responsibility, which matters if questions arise later. We confirm in writing whether we can accept a Principal Designer role on a given project, based on competence, scope and insurance.

What information clients should keep

Clients should keep the key project information: drawings, approvals, structural calculations, the building control completion certificate, warranties, and any health and safety information provided at handover. This record is valuable for maintenance, future works and any sale of the property.

What to ask before appointing a designer

Before appointing, ask which Principal Designer duties apply to your project, who will hold each, whether the designer is competent and insured to take on the role, and how the appointment will be documented. Clear answers at the outset prevent confusion during the project.

Frequently asked questions

Are the two Principal Designer roles the same?

No. One arises under CDM and concerns design-phase health and safety; the other arises under the Building Regulations and concerns design-stage compliance. A project may need one, both or neither.

Do I need a Principal Designer for work on my home?

It depends on the project. Domestic clients have specific, often reduced, duties, and the roles apply in defined circumstances. We advise on what applies to your project and what we can take on.