Principal Designer is a legal role, not a professional title. Two Acts create it. Under CDM 2015 a Principal Designer must be appointed on any project involving more than one contractor — almost every project, including domestic. Under the Building Safety Act 2022 (in force October 2023), a separate Principal Designer role applies to all projects requiring building regulations approval, with expanded duties on higher-risk buildings. Both must be appointed in writing. Non-appointment isn’t a defence — the duty defaults to the client personally under CDM 2015. Most homeowners have no idea this is the law.
The two roles
The CDM 2015 Principal Designer plans, manages and monitors health and safety through pre-construction. Duties include identifying, eliminating or reducing foreseeable design risks; coordinating other designers; preparing pre-construction information and the health and safety file.
The Building Safety Act Principal Designer coordinates design work in relation to building regulations compliance. On all projects: plan, manage and monitor design work so it complies. On higher-risk buildings: expanded duties as part of the gateway regime.
When each applies
CDM 2015 PD: any project with more than one contractor. Includes almost every project of any size, and includes domestic — the pre-2015 domestic exemption was removed.
BSA PD: all projects requiring building regulations approval. Expanded on higher-risk buildings (residential ≥18m or ≥7 storeys with ≥2 units).
On a typical domestic project, both apply. The same person can hold both, and often does — we take both on our full-service appointments as standard.
What the role actually does
Design risk management — foreseeable risks identified, eliminated where possible, otherwise recorded.
Coordination of other designers’ CDM duties across the team.
Pre-construction information prepared for the Principal Contractor.
Building regulations compliance coordinated across all designers on BSA-applicable projects.
Health and safety file compiled and handed over at completion.
What we deliver
- Formal Principal Designer appointment under CDM 2015, in writing
- Formal PD appointment under the Building Safety Act where applicable
- Design risk register maintained through design
- Pre-construction information document
- Coordination of other designers’ CDM duties
- Compliance coordination under the Building Safety Act
- Higher-risk building gateway support where applicable
- Health and safety file compiled at completion
How the process runs
Appoint
Role confirmed in writing at the start, as both regulations require.
Plan
Design risks identified from the beginning and designed out where possible.
Coordinate
Other designers’ CDM duties managed. BSA compliance coordinated across the team.
Record
Design risk register and PCI maintained through the design stages.
Hand over
Health and safety file compiled and passed to the client at completion.
Standards and regulations that apply
The primary references.
The primary CDM 2015 legislation. Duties in Regulations 4-16.
The HSE’s Approved Code of Practice for CDM 2015.
Creates the BSA PD role. Core duties commenced October 2023.
The regulations against which compliance is coordinated.
Introduced the BSA duty-holder regime.
The Building Safety Regulator’s guidance on higher-risk buildings and the golden thread.
Common questions
Does my house extension really need this? +
If more than one contractor is involved (almost every project once you count subcontractors), CDM 2015 requires a PD to be appointed in writing. The BSA PD duty also applies to any project needing building regulations approval, which includes almost every extension.
Is it included in your full-service fee? +
Yes. On full appointments we take both PD roles as standard. No separate charge.
Can you be PD on a project designed by someone else? +
Yes. Stand-alone PD appointments are quoted separately. We’re frequently appointed on this basis where the designer doesn’t hold the role.
What’s a higher-risk building? +
Broadly, residential buildings of ≥18m or ≥7 storeys with ≥2 units. Care homes and hospitals of similar height too. These fall under the BSA gateway regime with substantially stricter duties.
What’s the golden thread? +
Structured information about the building maintained through design, construction and occupation. Required on higher-risk buildings under the BSA. The PD is responsible for it through the design phase.
What if no PD is appointed? +
Under CDM 2015, duties default to the client personally. Under the BSA on higher-risk buildings, non-appointment can prevent gateway approvals. Non-appointment itself is a breach, enforceable by the HSE or BSR.
Do I need to appoint the PD in writing? +
Yes. Both roles require written appointment. A verbal appointment or an assumption that “the architect will handle it” does not discharge the duty.
What’s a Principal Contractor? +
A separate CDM 2015 duty-holder role, normally held by the main contractor and appointed by the client for the construction phase. Both a PD and a PC must be appointed on any project with more than one contractor.
Get in touch and we’ll confirm what applies to your project.