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Ask ten people on a UK project who the principal designer is and you will get a confident answer. Ask them which principal designer you mean and the confidence usually evaporates.
There are two. They are created by different legislation, they cover different things, they carry different competence requirements, and there is no rule that says the same organisation has to hold both. The Health and Safety Executive’s own review of CDM 2015, which reported in May 2026, identified confusion arising from “similar but distinct roles under the Building Safety Act” and inconsistent interpretation across the market as a live problem — and it is one of the few things in that review that generated a commitment to new guidance.
Until that guidance lands, the fix is contractual and it is straightforward. But you have to know what you are separating.
The CDM principal designer
Created by the Construction (Design and Management) Regulations 2015. Required on any project with more than one contractor.
The CDM PD plans, manages and monitors the pre-construction phase, and coordinates health and safety during it. That means identifying and eliminating foreseeable risks to anyone building, using, maintaining, cleaning or eventually demolishing the structure; ensuring designers carry out their own duties; preparing and providing pre-construction information; and preparing the health and safety file for handover.
Its subject is health and safety. Its window is pre-construction. Its statutory home is CDM 2015, with L153 as the approved code of practice.
The Building Regulations principal designer
Created by Part 2A of the Building Regulations, introduced by the Building Safety Act 2022 and in force since October 2023. Required on any project with more than one designer.
The BR PD plans, manages and monitors the design work so that, if built, the building would be compliant with all applicable requirements of the Building Regulations. Not just fire. Not just structure. All of them — Parts A through S, and whatever else applies.
Its subject is regulatory compliance of the design. Its window is the whole design process. Its statutory home is Part 2A, with regulation 11G setting the competence requirement.
Why people conflate them
Because the names are identical, the appointments often land on the same organisation, and the client duty to appoint looks superficially similar in both regimes. On a straightforward project with a lead architect doing both, nothing goes visibly wrong and the distinction never gets tested.
It gets tested when something is missed, and the question becomes which role was supposed to catch it. A fire compartmentation error is a Building Regulations compliance failure — BR PD territory. A design that requires a temporary works sequence nobody can execute safely is a CDM matter. A cladding specification that is both non-compliant and creates a construction-phase hazard sits in both. If the appointments never distinguished the roles, that argument gets had retrospectively, under pressure, with insurers in the room.
The competence requirement is not a formality
Regulation 11G requires a principal designer to have the skills, knowledge, experience and behaviours to fulfil all of the role’s duties. Where the PD is an organisation, it must have the organisational capability, and it must formally designate a competent individual to carry the role.
The competence framework sits in a set of published standards:
- BSI Flex 8670 — the core criteria for building safety competence frameworks, which the others sit on top of.
- PAS 8671:2022 — competence for individual Building Regulations principal designers. Four mandatory areas: behavioural competence, which explicitly includes the obligation to refuse work beyond your limits; the legislative and regulatory framework; management of design work compliance; and the technical framework. Higher-risk buildings carry additional thresholds covering golden thread management and mandatory occurrence reporting.
- PAS 8672:2022 — the equivalent for principal contractors.
- PAS 8673 — competence for managing safety in occupied residential buildings.
There is no mandatory registration scheme yet. That is not the same as there being no requirement — the duty is in the regulations today, and the client has a corresponding duty to check that you meet it. What is coming is the formalisation: MHCLG ran a call for evidence on a strategy for the built environment professions which closed on 12 August 2026, covering licensing and registration approaches directly, with the resulting strategy due in Spring 2027. Principal contractor licensing for higher-risk building work is being developed separately, and a review of the dutyholder regime is expected imminently.
Which means the evidence you assemble now is the evidence you will be assessed against later.
The design-and-build novation problem
This is where most of the real damage happens.
On a novated design-and-build project, the design team transfers to the contractor at some point after planning. The CDM principal designer role frequently moves at the same time, or the principal contractor picks it up. The BR principal designer role often moves too — sometimes deliberately, frequently by assumption, occasionally without anyone naming it in a document.
Three questions that need answering in writing before novation:
- Is the BR PD role transferring at all? It does not have to. The architect can retain it while the CDM PD role goes to the contractor, if that reflects who is actually managing design compliance.
- If it is transferring, is the receiving party competent under regulation 11G? A contractor’s design manager may be extremely capable and still not have a designated competent individual mapped against PAS 8671. The client has a duty to check this. Very few do.
- Who owns the design decisions made before novation? The BR PD duty runs across the design process, and a novation does not erase what happened at Stage 3.
For an architectural practice specifically: if you are not taking the Building Regulations principal designer role, say so in writing at appointment. Not in a covering email. In the appointment. The default assumption in the market is that the lead designer holds it, and rebutting that assumption after the fact is considerably harder than stating it at the start.
The change most designers have missed
The Construction Products Reform White Paper, published on 2 March 2026, does something significant to the BR PD role that has had very little attention.
It makes Building Regulations principal designers explicitly responsible for ensuring that what is specified and installed is suitable and safe for the intended use. Installers, and by extension principal contractors, carry responsibility for correct and appropriate installation. Manufacturers get new duties under a General Safety Requirement, with regulations expected by the end of 2026 and implementation in late 2027.
The practical consequence for a designer is that product specification is being pulled decisively inside the compliance duty. Which means the records that matter are:
- A product substitution register. What was specified, what was actually installed, who proposed the change, on what evidence it was accepted, and who accepted it.
- The evidence of suitability itself. Test data, certification, the conformity assessment body, and the intended use it was assessed against.
- The point at which you relied on someone else. Where a specialist subcontractor’s design or a manufacturer’s assurance was the basis of acceptance, record that it was.
Separately, government is developing options for strengthening principal designer accountability as part of its response to the Grenfell Inquiry. The direction is not subtle.
What your appointment should say
Four things, in terms:
- Which principal designer role is being taken — CDM, Building Regulations, both, or neither.
- By whom, named — the organisation and the designated competent individual, not just the practice.
- For what scope and what period — including what happens on novation, and whether the role transfers.
- What is expressly excluded — particularly where a specialist package carries its own designer and its own compliance responsibility.
And keep the design decision register from day one. Not because a regulation names it, but because every one of the arguments above is won or lost on whether the decision and its basis were recorded at the time.
The two roles are not difficult once separated. What is difficult is separating them retrospectively, on a project where something has gone wrong and three parties have a reason to believe the other one held the duty.
If you are taking on principal designer duties and want the appointment scope, the competence evidence and the design decision record set up properly at the front of the job, we do exactly that — as a standing arrangement or on a single project.