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Building Safety Act: what are the differences for architects between the CDM Principal Designer role and the Building Regulations equivalent?

Architects can learn more about the two dutyholder roles and the differences that make them distinct from one another.

28 March 2024

One of the most frequently asked questions by RIBA Members continues to reference the Principal Designer (PD) role defined by Building Regulations in England.

As the transition period to the new regime comes to an end on 6 April (2024), confusion still arises because the term ‘Principal Designer’ - introduced under the Construction (Design and Management) Regulations 2015 (CDM) - now applies to the new Building Regulations regime, creating one term with two completely separate and distinct sets of duties and regulatory requirements.

This has led some designers and their clients to initially regard the Building Regulations PD duties (BRPD) as an extension of the already established CDMPD duties when they are not. While under both regimes there is an underlying obligation to plan, manage and monitor, there are nuances that are important to each.

With RIBA encouraging members to take on both of these roles, it’s important to look at the main differences.

There are important differences between the CDM and Building Regulations Principal Designer roles to be aware of. (Photo: Canva)

What are the differences between the two Principal Designer roles under CDM and Building Regulations?

The CDMPD is responsible for planning, managing and coordinating health and safety during the pre-construction phase. This may involve working with different designers on a project to eliminate foreseeable health and safety risks during construction or taking steps to reduce and control potential risks.

CDM applies to all construction projects, including domestic projects, from concept to completion.

While the Health and Safety Executive (HSE) always expected the CDMPD role to be carried out by the lead designer, and many practices do offer this service, the 2015 regulations also saw the arrival of third-party consultants taking on the role.

This was perhaps amplified by many architects at the time not offering the CDMPD duties. However, the appetite and opportunity for architects to add this service has grown greatly in recent years (although some clients choose to use their own in-house team or third-party consultants for the role).

In contrast, the BRPD is required to plan, manage and monitor all design work during the design stage of a project to ensure that the design is compliant with the regulations. Again, the HSE expects these duties to be taken on by the lead designer, who must coordinate with other designers to achieve consensus that all design elements are compliant.

This requires the BRPD to be competent and to have the skills, knowledge, experience and behaviours necessary to fulfil the duties under the regulations. The duties of the BRPD should not be confused with the duties of the designer under this regime (though naturally if the one person is performing both duties their designer duties will still apply).

Read more about how to purchase RIBA’s Principal Designer Guide.

Are architects or Principal Designers under Building Regulations responsible for the building work?

Whether a designer or BRPD, your duties do not extend to responsibility for the building work. The Principal Contractor is responsible for ensuring that the building work is completed in accordance with the approved design. Each contractor is also responsible for ensuring that the work they undertake complies with the relevant regulatory requirements (under CDM and the Building Regulations).

While there are already third-party consultants starting to offer BRPD services, including some who previously provided CDMPD services before the Building Safety Act came into force in October 2023, the BRPD’s central role in coordinating design work is a different specialism and competency to the coordinating of design work for health and safety purposes.

RIBA strongly advises architects to make the BRPD role their own along with the CDMPD role, to further enhance and promote the protection of specialism and function.

Under CDM and the Building Regulations, a project’s main contractor is allowed by regulations to take on both the Principal Designer and Principal Contractor duties during the building work. Still, some contractors will not have the in-house design competence to do so. A contractor who agrees to be appointed BRPD without the requisite competence will be in breach of Regulations and may face sanctions imposed by the building control authority.

Whether a Designer, or BRPD, your duties do not extend to responsibility for the building work. (Photo:

RIBA’s Principal Designer Course (CDM and Building Regulations)

RIBA Principal Designer webinar series, which starts on 17 April (2024) on RIBA Academy will provide all practitioners – whether working on small or large projects – the essential skills they need to demonstrate competence in the Principal Designer role under CDM and the Building Regulations.

The redeveloped course will be delivered by experts including:

  • Nigel Ostime
  • Joan McCoy
  • David Brook
  • Paul Bussey
  • Keri Barr
  • Colin Blatchford-Brown
  • Dieter Bentley-Gockmann acting as key consultant

The course will help attendees show awareness and capability to deliver these roles there is an industry expectation for professionals to demonstrate competence.

Read more about the course and sign up on RIBA Academy.

The fact that the regulations allow a client to certify in writing that CDMPD becomes the BRPD could be a potential source of confusion. (Photo:

What are the implications of the new regime?

It is early days for the application of the new Building Safety Act regime. Joanna Lewis, partner at legal company Beale & Co, says the signs are that it is clients with a poor understanding of the new regulatory regime that are most likely to be conflating the BRPD and CDMPD roles and assuming that their usual CDM appointments can be readily extended to cover BRPD.

She believes that the fact that the regulations allow a client to certify in writing that CDMPD becomes the BRPD could be a potential source of confusion. It may not be at all appropriate to extend a CDMPD appointment if the appointed CDMPD does not have the relevant competence to carry out the duties of the BRPD. This is particularly the case where the CDMPD appointment is a third party rather than a lead designer.

“The legislation does allow for this, but the client needs to understand that there will be time and cost implications for the architect taking on the Principal Designer role for Building Regulations,” Joanna says. “Architects should be saying to clients: look, there are key differences between the two roles.”

Joanna suggests that other areas of potential confusion are a misconception that the BRPD role is primarily about safety (it is not, she contends - it covers Building Regulations as a whole) and that Principal Designers are only required on higher-risk buildings (HRBs) (they are not, she once again contends - they are required on most construction projects to which Building Regulations apply).

Joanna thinks the wording of the BRPD duties is much better than the consultation version of the regulations, which imposed an absolute requirement on the Principal Designer to ensure compliance, implying a legal liability that may have had PI implications.

“A key way of seeking to avoid confusion between the two roles is to write to your client at the outset of your appointment setting out the client’s key duties under the Building Regulations and CDM and the key differences between the roles,” she advises. “Given there is a requirement under both regulations for a designer to make the client aware of their duties this should be something architects are already doing but highlighting the differences may well be key.”

Want to read more about the Building Safety Act?

These professional features from the RIBA Practice team should help build a little more confidence in your part of the new regulatory regime in England:

Text by Neal Morris and the RIBA Practice team. Send us your feedback and ideas.

RIBA Core Curriculum topic: Legal, regulatory and statutory compliance.

As part of the flexible RIBA CPD programme, professional features count as microlearning. See further information on the updated RIBA CPD core curriculum and on fulfilling your CPD requirements as a RIBA Chartered Member.

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