Principal Contractor Appointment Letter

1. What Is a PC Appointment Letter?

A Principal Contractor Appointment Letter is the formal written document by which a client appoints a contractor to act as Principal Contractor on a construction project under CDM 2015.

Like the Principal Designer appointment, this is not optional and is not satisfied by a verbal agreement or a reference in the main building contract. CDM 2015 Regulation 5(1) is unambiguous: the appointment must be in writing. Without a written appointment, there is no legally effective Principal Contractor — and the client automatically becomes responsible for all PC duties.

“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 — ... (b) a contractor with control over the construction phase as principal contractor.”— CDM 2015 Regulation 5(1)(b)

The appointment letter does three things simultaneously. It creates the legal CDM duty holder relationship between client and Principal Contractor. It confirms that the PC has the skills, knowledge, experience and organisational capability required by CDM 2015 Regulation 8. And it defines the scope and duration of the engagement — critically, confirming that the PC accepts the duty to prepare the Construction Phase Plan before works start on site.

2. PC vs PD — The Distinction

CDM 2015 creates two parallel duty holder roles that must be appointed on any multi-contractor project: the Principal Designer and the Principal Contractor. They have distinct responsibilities, cover different phases of the project, and produce different documents. Understanding the distinction prevents the common mistake of assuming one appointment covers the other.

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. CDM 2015 Regulation 5(1)(b) is explicit: the client must appoint a principal contractor in writing.

The critical change from CDM 2007 is that the PC appointment is no longer limited to notifiable projects. Under CDM 2007, a PC was only required on projects notifiable to the HSE. Under CDM 2015, the duty applies to all multi-contractor projects regardless of size, duration, or value. This significantly expanded the number of projects requiring a formal PC appointment.

4. Who Can Be Appointed?

CDM 2015 Regulation 5(1)(b) requires the PC to be ‘a contractor with control over the construction phase.’ This sets three requirements:

• A contractor — they must fall within the CDM definition of a contractor, meaning any person who carries out, manages, or controls construction work. This includes the main contractor, a management contractor, or a design-and-build contractor.
• With control over the construction phase — they must have authority to direct and coordinate the construction works on site. This means practical control over how the work is carried out, not merely a contractual relationship.
• 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.

5. When Must the Appointment Be Made?

CDM 2015 requires the PC to be appointed as soon as practicable, and in any event before the construction phase begins. The timing is not just a formality — the PC must be in place early enough to prepare the Construction Phase Plan, which must exist before any work starts on site.

The ‘reasonably foreseeable’ threshold applies here too. If it is clear at the outset that more than one contractor will be involved, the PC should be appointed as early as possible — not just before the first day on site. Early appointment allows the PC to contribute to buildability, sequencing, and logistics during the pre-construction phase.

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.

The PC appointment letter is a separate document from the building contract, even though the same contractor typically holds both roles. A JCT or NEC contract that names a party as ‘principal contractor’ does not automatically satisfy the CDM 2015 written appointment requirement unless it explicitly references CDM 2015 Regulation 5(1)(b), confirms the PC's duties, and includes a competence confirmation. In practice, a standalone appointment letter or a clearly identified CDM schedule within the building contract is the safest approach.

7. What Are the PC's CDM Duties?

The PC's duties are set out in CDM 2015 Regulations 12 to 14. They cover the full range of construction phase management — from preparing the CPP to managing welfare, coordinating subcontractors, and contributing to the H&S File. The appointment letter should reference these duties explicitly so there is no ambiguity about what the PC is taking on.

8. Domestic Clients and the PC Appointment

Domestic clients — individuals having construction work done on their own home, not connected to a business — are subject to CDM 2015, but their specific client duties under Regulations 4 to 6 and 8 automatically transfer to other duty holders. The domestic client is not expected to make formal CDM appointments themselves.

9. Common Mistakes

10. How It Relates to Other Documents

The PC Appointment Letter sits within a wider framework of CDM documentation. Understanding the relationships ensures that each document serves its intended purpose and that none is substituted for another.

11. A Real-World Example

A commercial client commissioned the fit-out of a new retail unit in a shopping centre. The project involved stripping out the previous tenant's fixtures, installing new mechanical and electrical services, fitting out the sales floor, and constructing a mezzanine storage area. The client appointed a main contractor through a JCT Intermediate Building Contract. The contract named the contractor as ‘principal contractor’ in the recitals, but contained no reference to CDM 2015, no list of PC duties, and no competence confirmation. No separate PC appointment letter was issued.

The main contractor engaged three subcontractors: M&E, steelwork for the mezzanine, and shop fitting. During the mezzanine steelwork, an operative fell from an unprotected edge at 3.5 metres and sustained serious injuries. The HSE investigated. Among their findings: there was no written PC appointment under CDM 2015 Regulation 5(1)(b). The reference in the JCT contract was not sufficient — it did not confirm the PC's duties, did not include a competence check, and did not reference the specific CDM regulations. The Construction Phase Plan was inadequate and had not been prepared before works started. The client had not provided pre-construction information to the contractor.

The HSE took enforcement action against both the client and the contractor. The client was found to have failed to appoint a PC in writing, failed to provide pre-construction information, and failed to ensure a CPP was in place before works started. The contractor was found to have failed in its duties as the de facto PC — despite never having formally accepted the role.

A standalone PC appointment letter, properly prepared and signed before the construction phase began, would have cost nothing beyond the time to prepare it. Its absence cost both parties enforcement action, legal fees, project delays, and reputational damage — all of which were entirely avoidable.

12. Frequently Asked Questions