Principal Designer Under the Building Safety Act: Duties, Responsibilities and the BSR Interface

Of all the duty holder roles introduced by the Building Safety Act 2022, the Principal Designer (Building Regulations) has generated the most confusion — and the most risk for those who misunderstand it. It is frequently conflated with the CDM Principal Designer, delegated to the lead architect by default, or appointed far too late in the design process to discharge effectively. The consequences, at Gateway 2 stage, can be severe.

This article explains what the Building Regulations Principal Designer role actually requires, how it differs from the CDM role, what competence looks like in practice, and what the BSR will scrutinise when reviewing a Gateway 2 submission.

Two Principal Designers: The Distinction That Matters

Since the Building Safety Act, there are two distinct Principal Designer duties on any higher-risk building project:

The Building Safety Act 2022 created the Building Regulations Principal Designer role to ensure there is a single identifiable person responsible for coordinating Building Regulations compliance across the design team throughout the design phase. This is a substantively different obligation from the CDM role, and the two should not be casually merged.

The Legal Duties: What the BSA Requires

The Building Regulations 2010 (as amended by SI 2023/907) impose the following duties on the Principal Designer (Building Regulations) for higher-risk buildings:

Coordinate design work for compliance

The Principal Designer must plan, manage, monitor and coordinate the design phase to ensure that the design, as developed, complies with all applicable Building Regulations requirements. This is not a passive audit function — it requires active participation in design decision-making and the ability to challenge the design team when compliance risks are identified.

Maintain the Golden Thread

The Principal Designer is responsible, during the design phase, for ensuring that the Golden Thread of information — the comprehensive, structured record of all design decisions relevant to safety — is maintained and updated. This includes recording the basis for key design decisions, documenting changes and ensuring that information is held in a form that can be accessed and used at Gateway 3 and beyond.

Support Gateway applications

The Principal Designer must cooperate with the client and Principal Contractor in preparing the Gateway 2 submission. In practice, this means authoring or reviewing compliance statements, ensuring that duty holder information is accurate and complete, and confirming that the design documents submitted to the BSR accurately represent the designed scheme.

Change control

During the design phase and into construction, the Principal Designer must ensure that any changes to the design are assessed for their compliance implications before being implemented. This is not merely administrative — it requires technical judgment about whether a proposed change affects compliance with any Approved Document.

Competence Requirements

The most significant shift introduced by the Building Safety Act regime is the statutory competence requirement for duty holders. The Principal Designer must have the skills, knowledge, experience and behaviours to fulfil the role. For higher-risk buildings, this is assessed against the frameworks set out in BSI Flex 8670 (Competence of Individuals Working on Higher-Risk Buildings) and the RIBA/CABE guidance on Principal Designer competence.

In practice, the BSR expects to see evidence of:

• Demonstrable experience of Building Regulations compliance on comparable higher-risk building projects — not merely design experience generally
• Knowledge of the relevant Approved Documents and associated British Standards across multiple disciplines (structural, fire, accessibility, energy, etc.)
• An understanding of the Gateway 2 process and what is required of the Principal Designer within it
• A structured approach to coordinating compliance across multi-disciplinary design teams, including documented design review processes
• Familiarity with the Golden Thread concept and the information management obligations under the Building Safety Act

The BSR has been explicit that membership of a professional body — RIBA, RICS, IStructE — does not in itself constitute evidence of competence for this role. The assessment is specific to the Principal Designer (Building Regulations) function.

What the BSR Looks for in a Gateway 2 Submission

When reviewing a Gateway 2 application, the BSR's assessors will scrutinise the Principal Designer's contribution on several levels:

Has the Principal Designer been appointed in writing at an appropriate stage? Late appointments — at Stage 4, shortly before submission — are a red flag. The BSR will ask how the Principal Designer could have coordinated design compliance if they were not involved until the design was substantially complete.

Is there evidence of active design review? A Principal Designer who has genuinely fulfilled the role will have produced design review records, compliance tracking matrices, risk registers or equivalent documentation. A submission that contains compliance statements but no evidence of a coordinated design process is vulnerable to requisition.

Do the competence documents meet the required standard? The Principal Designer's competence evidence must be specific and substantive. The BSR has issued requisitions where competence evidence consisted of a CV and a professional membership certificate without further detail.

Is the Golden Thread started? The Gateway 2 submission should include at least an outline of how the Golden Thread will be maintained through construction. A Principal Designer who cannot articulate their approach to information management at Gateway 2 stage has likely not engaged seriously with the role.

Common Failures

The following failures are consistently identified in BSR Gateway 2 requisitions relating to the Principal Designer role:

• Appointment too late. The Principal Designer must be appointed no later than RIBA Stage 3. Appointments at Stage 4 or during the Gateway 2 preparation period are almost always insufficient.
• No documented design review process. The Principal Designer must be able to demonstrate, with contemporaneous records, that design reviews were conducted with a compliance focus throughout the design phase.
• No change control records. Changes to the design between RIBA stages should be recorded and assessed. A submission that shows a design that has clearly evolved but contains no change assessment records is problematic.
• Conflation with CDM PD. Where a single individual is acting as both CDM Principal Designer and Building Regulations Principal Designer, the submission must demonstrate clearly that they hold competence for both roles. Many requisitions arise because this dual-role appointment has been made without any analysis of whether the individual is competent to fulfil the Building Regulations PD function.
• No engagement with the Golden Thread. A Gateway 2 submission that says nothing meaningful about how the Golden Thread will be maintained — or that simply refers to the project's document management system without explaining what information will be captured — is likely to draw a requisition.

Applicable Legislation and Guidance

The Principal Designer (Building Regulations) role is one of the most substantive and legally consequential positions on any higher-risk building project. Appointing the right person, at the right time, with the right evidence of competence — and then ensuring they genuinely fulfil the role — is not optional. It is the foundation on which a credible Gateway 2 submission is built.