CDM 2015 Core · Mandatory · Pre-Construction
Principal Designer Appointment Letter
This appointment letter formally designates the principal designer for a construction project as required under CDM 2015. The client must appoint a principal designer with the skills, knowledge, and experience to fulfil the role. The letter should clearly set out the scope of duties, responsibilities, and authority.
Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. CDM 2015 Reg 5 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.
| Legal basis | CDM 2015 Regulation 5(1)(a) — written appointment mandatory |
| When required | Any project with more than one contractor, or where more than one contractor is reasonably foreseeable |
| Who appoints | The client — this duty cannot be transferred |
| When | As soon as practicable — ideally at concept/RIBA Stage 2; must be before construction phase begins |
| Must be in writing | Yes — CDM 2015 Regulation 5(1) explicitly requires written appointment |
| Competence required | CDM 2015 Reg 8 — skills, knowledge, experience and (if org) organisational capability |
| If client fails to appoint | Client automatically takes on PD duties (commercial). Designer in control of pre-construction phase becomes PD (domestic). |
| Enforcing authority | Health and Safety Executive (HSE) |
1. What Is a Principal Designer Appointment Letter?
A Principal Designer Appointment Letter is the formal written document by which a client appoints an organisation or individual to act as Principal Designer on a construction project under CDM 2015.
It is not optional, it is not implied by an existing design appointment, and it is not satisfied by a verbal agreement. CDM 2015 Regulation 5(1) is explicit: the appointment must be in writing. Without a written appointment, there is no legally effective Principal Designer — and the client becomes responsible for all PD duties themselves.
“Where there is more than one contractor, or if it is reasonably foreseeable that more than one contractor will be working on a project at any time, the client must appoint in writing — (a) a designer with control over the pre-construction phase as principal designer...”— CDM 2015 Regulation 5(1)(a)
The appointment letter does three things simultaneously. It creates the legal CDM duty holder relationship between client and Principal Designer. It confirms that the PD has the skills, knowledge, and experience to carry out the role. And it defines the scope and duration of the engagement so there is no ambiguity about what the PD is — and is not — responsible for.
2. Important: There Are Now Two ‘Principal Designer’ Roles
Building Safety Act 2022 — October 2023 change
Since 1 October 2023, a second ‘Principal Designer’ role exists under the Building Regulations (Building etc. (Amendment) (England) Regulations 2023), separate from the CDM Principal Designer role. Both use the same title. Both are required on most projects with more than one contractor. They have different duties, different competence requirements, and different regulators. This guide covers the CDM Principal Designer only.
| Aspect | CDM Principal Designer | Building Regulations Principal Designer |
|---|---|---|
| Enabling legislation | Construction (Design and Management) Regulations 2015 | Building etc. (Amendment) (England) Regulations 2023 (under the Building Safety Act 2022) |
| Purpose | Health and safety during construction | Building regulations compliance (fire safety, structural integrity, energy performance, etc.) |
| Regulator | Health and Safety Executive (HSE) | Building control body (local authority or registered building control approver) |
| When required | Any project with more than one contractor (or where more than one is reasonably foreseeable) | Any project requiring a building regulations application where more than one designer is involved |
| Who can hold the role | A designer with control over the pre-construction phase | A registered building inspector, architect, or other competent professional — must be a designer |
| Can one person hold both? | Yes — if competent for both roles | Yes — if competent for both roles |
| This guide covers | Yes | No — separate appointment required |
For most SME construction projects, the CDM Principal Designer is the role covered by this guide. If your project also requires a building regulations application, you will need to consider both roles and may need separate appointments for each — even if the same person or organisation fills both.
3. Is It a Legal Requirement?
Yes — the written appointment is mandatory on any project involving more than one contractor, or where it is reasonably foreseeable that more than one contractor will work on the project at any time.
The ‘reasonably foreseeable’ threshold is important and often missed. A project that starts with a single contractor but where it is foreseeable at the outset that additional contractors will be needed — for example, specialist subcontractors for M&E, roofing, or groundworks — triggers the duty to appoint a Principal Designer from the start. Waiting until the second contractor actually arrives on site is too late.
| Written appointment required | Any project with more than one contractor, or where more than one contractor is reasonably foreseeable at any time during the project |
| Appointment not required | A project where only one contractor will carry out the entire works and no additional contractors are reasonably foreseeable |
| Consequence of no appointment | Commercial client: client takes on all PD duties. Domestic client: the designer in control of the pre-construction phase becomes PD automatically. |
| Competence check required | Yes — CDM 2015 Reg 8 requires the client to take reasonable steps to satisfy themselves the PD has the necessary skills, knowledge, experience, and (if an organisation) organisational capability |
| PD must refuse if not competent | Yes — a designer must not accept appointment as PD unless they have the skills, knowledge, and experience to fulfil the role (CDM 2015 Reg 8(3)) |
4. Who Can Be Appointed as Principal Designer?
CDM 2015 Regulation 5(1)(a) requires the PD to be ‘a designer with control over the pre-construction phase.’ This sets three requirements:
- A designer — they must fall within the CDM definition of a designer, meaning a person who prepares or modifies a design, or who arranges for or instructs another person to do so. This includes architects, engineers, building services consultants, interior designers, and others who make design decisions affecting the project.
- In control of the pre-construction phase — they must have authority to coordinate health and safety matters during the design and planning stages. This means practical control over design coordination, not merely an advisory role.
- Competent — CDM 2015 Reg 8 requires skills, knowledge, and experience (and, for an organisation, organisational capability) appropriate to the project. The client must take reasonable steps to verify this before making the appointment.
Who typically holds the CDM PD role?
In practice, the CDM Principal Designer role is most commonly held by the lead designer on the project — typically the architect, civil or structural engineer, or building services consultant who already has control over design coordination. This makes practical sense because the PD must have genuine authority to coordinate the pre-construction phase, and the lead designer already holds this position.
A standalone H&S consultant is not automatically a suitable PD
A health and safety consultant who is not a designer and does not have control over the pre-construction phase cannot be appointed as Principal Designer under CDM 2015. The regulations require the PD to be a designer with control — not merely an advisor. If a standalone H&S consultant is appointed, the appointment may be legally ineffective, leaving the client as PD by default. An H&S consultant can support the PD, but they cannot replace a designer in the role unless they also meet the design and control requirements.
5. When Must the Appointment Be Made?
As soon as practicable. The PD should be in place early enough to influence the design process and coordinate health and safety from the outset — not brought in as an afterthought once design decisions have already been made.
| HSE guidance timing | As soon as practicable — the PD should be appointed early enough to be involved in design decisions from the start |
| RIBA Plan of Work timing | Ideally at RIBA Stage 2 (Concept Design) or earlier — the PD needs to influence design before key decisions are locked in |
| Absolute latest | Before the construction phase begins — CDM 2015 Regulation 5(4) states that the PD must be appointed before the construction phase |
| Reasonably foreseeable rule | If it is reasonably foreseeable at the outset that more than one contractor will be needed, the PD must be appointed immediately — not when the second contractor actually starts |
| If PD appointment ends early | The client must appoint a replacement PD for the remainder of the project, or the client takes on PD duties themselves |
6. What Must the Appointment Letter Contain?
CDM 2015 does not prescribe a specific format or template for the appointment letter. However, for the appointment to be legally effective and practically useful, it must contain enough detail to clearly establish the identity of the parties, the scope of the role, the duties being taken on, and the duration of the engagement.
| Element | Detail | Status |
|---|---|---|
| Project details | Name, address, and brief description of the construction project | Essential |
| Client identity | Full legal name and address of the client making the appointment | Essential |
| PD identity | Full legal name and address of the designer or organisation being appointed as PD | Essential |
| Scope | Clear description of which parts of the project the PD appointment covers — especially important on phased projects or where the PD role may not extend to all works | Essential |
| Duration | Start date of the appointment and the point at which it ends (e.g., practical completion, handover of the H&S File, or a specified date) | Essential |
| PD's duties | List of the PD duties under CDM 2015 Regulations 11 and 12 that the appointee is taking on — reference to the specific regulations is recommended | Essential |
| Competence confirmation | Statement confirming the PD has the skills, knowledge, experience, and (if an organisation) organisational capability to fulfil the role on this project | Essential |
| Fee and payment | Agreed fee or fee basis for the PD role, payment terms, and any conditions | Recommended |
| Insurance | Confirmation of professional indemnity insurance adequate for the PD role | Recommended |
| Client duties transfer | Where the client is a domestic client, confirmation of whether the PD is taking on client duties under CDM 2015 Reg 7(1)(b) by written agreement | Where applicable |
| Handover obligations | Confirmation that the PD will prepare and hand over the H&S File at the end of the project, and the format in which it will be delivered | Essential |
| Building Regs PD | Confirmation of whether the appointee is also acting as the Building Regulations Principal Designer, or whether that is a separate appointment | Recommended |
| Signed acceptance | Signature of both parties confirming agreement to the terms of appointment | Essential |
The competence confirmation deserves particular attention. CDM 2015 Reg 8 requires the client to take reasonable steps to satisfy themselves that the PD is competent. The appointment letter should include a clear statement from the PD confirming their competence, and should record what steps the client took to verify this — for example, review of qualifications, relevant project experience, professional body membership, or organisational capability assessment.
7. What Are the Principal Designer's Duties?
The PD's duties are set out primarily in CDM 2015 Regulations 11 and 12. They are design-phase focused but extend beyond design into construction where the PD's appointment continues. The appointment letter should reference these duties explicitly so there is no ambiguity about what the PD is taking on.
Plan, manage, monitor and coordinate health and safety
The PD must plan, manage, monitor, and coordinate health and safety in the pre-construction phase. This means actively managing how design decisions affect buildability and safety — not simply reviewing designs after they have been completed. The PD must ensure that the design process itself is coordinated so that risks are identified and eliminated or reduced at source.
Assist the client in providing pre-construction information
The PD must help the client identify and compile the pre-construction information that must be provided to designers and contractors. This includes information about the site, existing structures, hazardous materials, and any other health and safety information relevant to the project.
Ensure designers comply with their duties
The PD must ensure that all designers on the project comply with their duties under CDM 2015 Regulation 9 — including eliminating foreseeable risks where possible, reducing risks that cannot be eliminated, and providing information about remaining risks to those who need it.
Facilitate cooperation and coordination
The PD must ensure cooperation between all persons working in relation to the pre-construction phase, and coordinate their work to ensure the health and safety of those carrying out, or affected by, the construction work.
Prepare and maintain the Health and Safety File
The PD must prepare a Health and Safety File appropriate to the characteristics of the project, and must review, update, and revise it as the project progresses. At the end of the project, the PD must pass the completed H&S File to the client.
Liaise with the Principal Contractor
The PD must liaise with the Principal Contractor for the duration of their appointment, sharing information relevant to the planning, management, monitoring, and coordination of the construction phase. This includes providing information needed for the Construction Phase Plan.
Advise the client of their duties
The PD should assist the client in understanding their own CDM duties — including the duty to provide pre-construction information, to ensure adequate welfare facilities are provided, and to ensure that the construction phase does not start unless a Construction Phase Plan has been prepared.
The PD's role continues beyond RIBA Stage 3
A common misconception is that the PD's duties end when the design is complete. In fact, CDM 2015 requires the PD to continue liaising with the Principal Contractor and updating the H&S File during the construction phase, unless their appointment is formally ended and a replacement PD is appointed. If the PD's contract ends at RIBA Stage 4 or 5, the appointment letter should address what happens next — either the PD's appointment is extended, or a new PD is appointed, or the client takes on PD duties.
8. What If There Is No Appointment?
The consequences of failing to make a written PD appointment depend on whether the client is commercial or domestic, but in both cases, the PD duties do not disappear — they fall on someone else by default.
| Commercial client — no appointment | The client takes on all PD duties themselves. Most commercial clients are not equipped for this and will be in breach of multiple CDM regulations from the outset. |
| Domestic client — no appointment | The designer in control of the pre-construction phase becomes PD automatically (CDM 2015 Reg 5(3)). This may happen without the designer's knowledge or consent — they become PD by default, with full legal duties. |
| Enforcement risk | The HSE can take enforcement action against the client for failing to appoint a PD, and against any designer who takes on PD duties without the competence to fulfil them. Both are criminal offences under CDM 2015. |
| Design team without written appointment | If the design team proceeds without a written PD appointment, it is unclear who holds the PD role. In an HSE investigation, this ambiguity works against everyone — the client for failing to appoint, and the designer who may be deemed to have been acting as PD without formal acceptance. |
9. Common Mistakes
Assuming the design appointment covers the PD role
A standard design services agreement (such as an RIBA or ACE appointment) does not constitute a PD appointment under CDM 2015. The PD role must be separately and explicitly appointed in writing. A design appointment that does not reference CDM 2015 Regulation 5(1)(a) does not create a PD.
Appointing the PD too late
The PD must be in place early enough to influence design decisions. Appointing the PD after the design is substantially complete, or just before construction begins, means they cannot fulfil their primary duty of coordinating health and safety during the pre-construction phase.
Appointing a standalone H&S consultant as PD where they have no design role
CDM 2015 requires the PD to be a designer with control over the pre-construction phase. A standalone H&S consultant who does not prepare or modify designs and has no control over the design process does not meet the statutory definition and cannot legally hold the PD role.
Not checking competence before appointing
CDM 2015 Reg 8 requires the client to take reasonable steps to satisfy themselves of the PD's competence. Simply appointing the lead designer without any competence check is a breach. The appointment letter should record what steps were taken.
Confusing the CDM PD role with the Building Regulations PD role
Since October 2023, two separate PD roles exist. They have different legal bases, different regulators, and different duties. Appointing someone as CDM PD does not make them the Building Regulations PD, and vice versa. Both may need separate appointments.
Not addressing what happens if the PD appointment ends early
If the PD's engagement ends before the project is complete — for example, if their design services contract concludes at RIBA Stage 4 — the appointment letter should specify how PD duties will be transferred. Without this, the client becomes PD by default.
11. Frequently Asked Questions
Is the PD appointment always required in writing?▾
Yes. CDM 2015 Regulation 5(1) explicitly states that the client must appoint the Principal Designer "in writing." A verbal agreement, an implied appointment through an existing design contract, or a handshake arrangement does not satisfy the legal requirement. Without a written appointment, there is no legally effective PD.
Can the architect be appointed as both designer and PD in one document?▾
Yes — provided the document clearly identifies and separately addresses the PD role under CDM 2015. A standard RIBA or ACE design appointment does not automatically include the PD role. The PD duties must be explicitly stated, the scope defined, and the competence confirmation included. Many practices use an addendum or schedule to their standard design appointment for this purpose.
What if I don't appoint a PD when one is required?▾
If you are a commercial client and fail to appoint a PD, you take on all PD duties yourself. If you are a domestic client, the designer in control of the pre-construction phase becomes PD by default. In both cases, failing to make a required appointment is a breach of CDM 2015 and may result in HSE enforcement action.
Can the contractor be the Principal Designer?▾
Only if the contractor meets the definition of a designer with control over the pre-construction phase. In a design-and-build contract where the contractor takes on design responsibility, they may be eligible — but only if they have genuine control over the design process and are competent to coordinate pre-construction health and safety.
Does the PD need to be registered with a professional body?▾
CDM 2015 does not require registration with any specific professional body. The test is competence — skills, knowledge, experience, and organisational capability. However, membership of a relevant professional body (such as RIBA, ICE, or IOSH) may be evidence of competence and is commonly checked as part of the client's reasonable steps under Reg 8.
What happens if the PD's appointment ends before the project is complete?▾
The client must appoint a replacement PD for the remainder of the project. If no replacement is appointed, the client takes on PD duties (commercial) or the designer in control of the pre-construction phase becomes PD by default (domestic). The outgoing PD must hand over all relevant information, including the draft H&S File, to the incoming PD or client.
Is the CDM PD the same as the Building Regulations PD?▾
No. Since 1 October 2023, two separate Principal Designer roles exist. The CDM PD is appointed under CDM 2015 and focuses on health and safety during construction. The Building Regulations PD is appointed under the Building etc. (Amendment) (England) Regulations 2023 and focuses on building regulations compliance. They have different legal bases, different regulators (HSE vs building control), and different duties. One person can hold both roles if competent for each, but separate appointments are needed.
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