The developer behind a three-storey office refurbishment had been the project’s principal designer for four months and had no idea. Asbestos survey done, soft strip due in a fortnight, five trades on the programme. He had an architect, a project manager, a quantity surveyor and a health and safety consultant all on fees, and he had appointed none of them in writing. CDM 2015 is blunt about what follows: where the client makes no appointment, the client holds the duties.
The role is narrower than most people assume. Under the Construction (Design and Management) Regulations 2015, the principal designer is the designer appointed in writing by the client to plan, manage and monitor health and safety through the pre-construction phase of a project involving more than one contractor. The work is to get risk out of the design while the design is still cheap to change, then pass on whatever cannot be removed to the people who will build the structure and later maintain it.
One thing needs settling first, because it derails a lot of appointment paperwork. Two unrelated roles in UK law now use this job title.
Two unrelated roles now share the name principal designer
The Building Safety Act 2022 created a dutyholder regime under the Building Regulations, in force since October 2023, and it uses the same words. Different role, different purpose. The CDM principal designer deals with health and safety risk arising from construction, use and maintenance. The Building Regulations principal designer is there to plan, manage and monitor the design work so that the design, if built out, would comply with the Building Regulations.
| CDM principal designer | Building Regulations principal designer | |
|---|---|---|
| Legislation | CDM 2015 | Building Regulations, under the Building Safety Act 2022 regime |
| Concerned with | Health and safety risk in construction, use and maintenance | Compliance of the design with the Building Regulations |
| Appointment trigger | More than one contractor | More than one contractor or designer on work subject to the Building Regulations |
| Key output | Health and safety file; risk designed out | Evidence that the design complies |
One organisation can hold both, and frequently does. The appointments are still separate, the competence requirements are assessed separately, and appointing someone under CDM does not appoint them under the Building Regulations. So if your appointment letters cite CDM 2015 and nothing else, check the Building Regulations side on anything currently in design. The gap turns up quietly on projects that started before October 2023 and are still running.
Anyone waiting for the duplication to be tidied up should stop waiting. HSE’s post-implementation review of CDM 2015 concluded this year that the regulations remain fit for purpose, made no regulatory changes, and explicitly ruled out combining the CDM principal designer role with the Building Safety Act one. New guidance is promised on client obligations and on principal designer competence, but the position on the roles themselves is settled: two appointments, made separately, for the foreseeable future.
Principal designer duties under CDM 2015
Seven duties. Only one of them is a document.
| Duty | What it means on the job |
|---|---|
| Plan, manage and monitor the pre-construction phase | Own health and safety coordination across the design programme, not just at gateways |
| Identify and eliminate foreseeable risks | Apply the general principles of prevention; design risk out where reasonably practicable, then reduce and control what is left |
| Ensure designers comply with their duties | Including specialist, subcontract and temporary works designers who join late |
| Coordinate and cooperate | Make sure designers talk to each other and to the client about buildability and residual risk |
| Assist with pre-construction information | Help the client assemble it and get it to designers and contractors early enough to be useful |
| Liaise with the principal contractor | Share design information affecting planning and construction throughout the project, not only at handover |
| Prepare the health and safety file | Build it as the project progresses; hand it over for the client to retain |
The health and safety file deserves its own note. It is required wherever more than one contractor is involved, and it is written for whoever does the next job on the structure: a refurbishment contractor in fifteen years, or a demolition contractor in forty. Where the principal designer’s appointment ends before the project does, the file passes to the principal contractor, who hands it to the client at completion.
Who appoints the principal designer, and when?
The client appoints, in writing, whenever a project involves or is reasonably expected to involve more than one contractor. That is the only trigger. Neither project value nor duration changes it, and nor does whether the job is notifiable to the HSE, which is where a lot of people go wrong.
The F10 notification does not trigger the appointment. Notifiability is a size test: construction lasting more than 30 working days with more than 20 workers on site at the same time, or exceeding 500 person days. The principal designer test counts contractors, not days or workers. A small non-notifiable refurbishment with three trades on it still needs one.
Timing should follow the design: as early in the process as possible. Appointing at tender stage, when the design is largely fixed, means the role can no longer do the thing it exists to do.
And where the client appoints nobody, the client is treated as holding the principal designer’s duties. Not the architect who happened to be leading the design. Not the safety consultant who wrote the risk register. The client.
A health and safety consultant cannot hold the role
The principal designer has to be a designer: an organisation or individual who prepares or modifies designs, or arranges for or instructs someone else to do so. A health and safety consultant who does no design work cannot lawfully hold the appointment, though plenty of them do valuable work supporting whoever does. The duty stays with the designer.
On competence, CDM requires the client to satisfy themselves that anyone they appoint has the skills, knowledge and experience, and for an organisation the organisational capability, to carry out the role. There is no statutory register or single qualification behind it. Sensible clients look for design experience in the relevant sector and evidence that the firm can coordinate a live design team, rather than a consultant who arrives at the end of Stage 4 with a report.
The realistic candidates are the lead designer, the architect, the engineer, or the in-house design function of a design-and-build contractor. Whoever takes it needs real authority over the pre-construction phase. An appointment without authority is paperwork.
What separates the principal designer from every other designer
Every designer on a project carries CDM duties. Regulation 9 requires any designer preparing or modifying a design to take account of the general principles of prevention, eliminate foreseeable risks so far as is reasonably practicable, and provide information about the risks that remain.
The principal designer carries all of that plus a coordination duty on top. Being answerable for your own drawings is one job. Being answerable for the interfaces between everybody’s drawings is a different one, and it is the job CDM created the role to do.
Where design-stage information breaks down
Four information products come out of the role. Pre-construction information, assembled with the client and issued early enough that designers and contractors can use it. Design risk information, recorded where it will be read, which means on the drawings and in the specification rather than only in a standalone register. Input to the construction phase plan, which the principal contractor writes but cannot write well without design information the principal designer holds. And the health and safety file, assembled progressively and issued at handover.
Consider what happens when one of those stalls. A structural engineer notes at Stage 3 that a section of first-floor slab was cored and patched during an earlier fit-out and now carries a load restriction. It goes into the design risk register. The register is never worked into the pre-construction information, and the drawing note is lost in a later revision. Eight months on, a strip-out subcontractor tracks a three-tonne excavator across that slab, because nothing in the RAMS or the drawings told anyone not to.
That is the chain the principal designer sits at the top of. Design risk information feeds the risk assessments and method statements each contractor writes, which in turn set up the point of work risk assessments done at the workface.
Where AI helps, and where it does not
Spotting hazards is not the hard part of this role. Keeping information consistent across a design that keeps moving is, and the document set spans years: pre-construction information, design risk records, construction phase plan input and the health and safety file all describe the same project, and all drift apart as the design changes.
Assistive AI suits that particular problem. It can hold one consistent set of project facts across the document family, draft first versions of routine pre-construction information from records the business already holds, flag where a design revision has left downstream risk information stale, and make years of project records searchable when the health and safety file has to be assembled.
It does not take on the duty. A competent designer reviews and owns every output. And in compliance work this is a capability rather than a measured result: Surtori’s measured outcomes sit in estimating, which is a different problem with a different evidence base. AI in construction sets out which applications have evidence behind them.
Principal designer FAQs
Is a principal designer needed on every project?
No. Only where more than one contractor is involved. On a single-contractor project there is no principal designer to appoint, though every designer still carries their design duties under regulation 9.
Can the principal contractor also be the principal designer?
Yes, provided they are a designer and have the skills, knowledge, experience and organisational capability the project needs. Standard practice on design and build. Two roles, two written appointments, and they stay distinct.
What happens if the client does not appoint a principal designer?
The duty defaults to the client. It is a common oversight on projects where everyone assumed the lead designer had picked the role up informally, and the client inherits a coordination job they are rarely resourced to do.
When should the principal designer be appointed?
As early as the design allows.
Does the principal designer need to visit site?
CDM does not require it. The duty to liaise with the principal contractor runs through construction though, and design changes made during the build still have to be coordinated, so a role conducted entirely by email tends to show.
Is the CDM principal designer the same as the Building Regulations principal designer?
No. Separate legislation and separate appointments, even where one organisation holds both.
The load is in keeping it current
Most design teams get the appointment right and then lose the money downstream: the same project facts rekeyed across four document sets, and a health and safety file assembled from scratch at handover because nobody built it as they went. That is an operating model problem.
The full CDM 2015 duty-holder guide shows how the role fits the wider regime, and the same load on the construction side is covered in the guide to the principal contractor. For demolition and strip-out packages, see our operational efficiency work with demolition contractors. Book a discovery call if you want us to look at where your design-stage documentation costs you time.