Building Regulations
Building Regulations and CDM principal designers compared
Short answer
They are two separate appointments under two separate sets of regulations. The Building Regulations principal designer, under Part 2A of the Building Regulations 2010, coordinates the design so the building work would comply with the Building Regulations. The CDM principal designer, under regulation 5 of the Construction (Design and Management) Regulations 2015, deals with health and safety through the pre-construction phase.
Both are triggered by the same test, more than one contractor, and both have the same default for a homeowner who appoints nobody. Appointing someone to one role does not appoint them to the other, unless the client certifies under regulation 11D(2) of the Building Regulations that its CDM principal designer is treated as appointed to the Building Regulations role.
Side by side
| Building Regulations principal designer | CDM principal designer | |
|---|---|---|
| Legislation | Building Regulations 2010, Part 2A, regulation 11D(1) | CDM 2015, regulation 5(1)(a) |
| In force in England | 1 October 2023 | 6 April 2015 |
| Purpose | Design that, if built, complies with the Building Regulations (regulation 11M(1)) | Health and safety in the pre-construction phase (CDM regulation 11(1)) |
| Work it covers | "Building work" as defined in regulation 3 | "Construction work" as defined in CDM regulation 2, which includes repair, redecoration, maintenance and demolition |
| When required | More than one contractor, or reasonably foreseeable (11D(1)) | The same test (CDM regulation 5(1)) |
| Appointed by when | Before the construction phase begins (11D(3)(b)) | As soon as practicable, and before the construction phase begins (CDM regulation 5(2)) |
| Who can hold it | A designer with control over the design work, competent for the role (11D(1), 11F, 11G) | A designer with control over the pre-construction phase (CDM regulation 5(1)(a)) |
| Homeowner appoints nobody | The designer in control of the design phase (11C(2)(a)) | The designer in control of the pre-construction phase (CDM regulation 7(2)(a)) |
| Business client appoints nobody | The client carries the duties until it appoints (11D(5)) | The client carries the duties (CDM regulation 5(3)) |
| Where the duties sit | Regulation 11M, on top of the designer duties in 11J and 11K | CDM regulations 11 and 12 |
| Work outside it | No client duties, so no appointment, where the work is only Schedule 4 minor work (11P) | No exclusion for minor work: the trigger is the contractor count |
| Who is told | Building control: the application (14(1)(c)), later appointments (11O) and the completion notice (16(4A)(e)) | Not part of the Building Regulations paperwork, unless certified under 11D(2) |
Where the two overlap
Part 2A follows the CDM structure closely: a client, a principal designer, a principal contractor, appointments in writing, and a default for domestic clients. Even the phases match. Part 2A defines the "design phase" as any period during which design work is carried out, which "may continue during the construction phase" (regulation 11Q). CDM defines the "pre-construction phase" in almost the same terms, adding preparatory work.
On a typical house extension with a design practice leading and a builder using subcontractors, both defaults often land on the same designer if the homeowner appoints nobody. That is how one firm can end up holding both roles without anyone choosing it. Whether that is safe is covered in can one person hold both roles.
Where they part company
- The work. Repainting the outside of a house with two decorating firms is construction work under CDM, because the definition includes redecoration. It is not building work under regulation 3, so Part 2A has nothing to say about it.
- Minor work. A client whose project is only Schedule 4 work, such as laying loft insulation on its own, is not bound by Part 2A (regulation 11P), however many firms take part.
- Competence. Part 2A sets its own tests: skills, knowledge, experience and behaviours to design work that complies (11F), and to carry out the principal designer duties (11G). Competence in health and safety coordination is not competence in Building Regulations compliance, and the reverse is also true.
- The paper trail. The Building Regulations role is named to building control and signs a declaration at the end. The CDM role is not part of that exchange.
ClearCDM compares the same two roles from the CDM side, including the CDM duties this page leaves out: CDM principal designer vs Building Regulations principal designer.
What this means for you
On any project with more than one contractor, expect two principal designer appointments, and make each one in writing, naming the regulations it is under. If one firm is to hold both, say so for each role. If you rely on the domestic defaults, check which designer is actually in control of the design, because that is who the law picks.
This guide covers England; Wales has its own dutyholder provisions for Building Regulations. Parallel Architecture coordinates Building Regulations information as part of its design work. Get in touch to talk a project through.
Sources
- Building Regulations 2010, Part 2A: dutyholders and competence legislation.gov.uk
- Building Regulations 2010, regulation 3: meaning of building work legislation.gov.uk
- CDM 2015, regulation 2: interpretation legislation.gov.uk
- CDM 2015, regulation 5: appointment of the principal designer and the principal contractor legislation.gov.uk
- CDM 2015, regulation 7: application to domestic clients legislation.gov.uk
- CDM 2015, regulation 11: principal designer duties legislation.gov.uk
- ClearCDM: CDM principal designer vs Building Regulations principal designer clearcdm.co.uk