Principal Designer vs Principal Contractor on small jobs: who does what and how to stay compliant

Quick answer

From 1 October 2023, for most building work in England with more than one contractor, clients must appoint in writing:

• a Principal Designer (PD) to plan, manage and monitor the design so it would comply if built; and
• a Principal Contractor (PC) to plan, manage and monitor the build so it complies.

On domestic work, if the client does not appoint, the designer in control becomes PD and the contractor in control becomes PC by default. See the official GOV.UK guide to design and building work: meeting building requirements and the legal text in The Building Regulations 2010, Part 2A.

When you must appoint a PD and PC

• More than one contractor involved? Appoint PD and PC in writing before construction starts. You can certify your CDM PD/PC as your Building Regulations PD/PC if they are competent for both. Sources: GOV.UK guidance and SI 2023/911 Regulation 6.
• One contractor only? That contractor is treated as the PC by default. If there is only one designer, they may have to fulfil PD duties. Legal basis: Regulation 11D and 11M–11N.

Domestic jobs: what if the client does nothing?

For domestic clients, if no appointments are made:

• the designer in control is PD automatically; and
• the contractor in control is PC automatically.

That’s straight from Part 2A. See the GOV.UK page’s ‘Domestic clients’ section and the legislation cross‑heading ‘Duties of dutyholders’ in Part 2A.

What the PD must actually do

Plain English summary of the PD role under Part 2A:

• Plan, manage and monitor the design work.
• Coordinate designers so the design, if built, will comply with relevant requirements.
• Share information with the PC and help the client understand duties.
• When your appointment ends, hand over a short document explaining your arrangements.

References: Part 2A duties sections for PD [11M] and general duties [11J–11L] in legislation.gov.uk.

What the PC must actually do

Plain English summary of the PC role under Part 2A:

• Plan, manage and monitor the construction work.
• Coordinate contractors so the work complies with the Building Regulations.
• Share information with the PD and help the client understand duties.
• When your appointment ends, hand over a short document explaining your arrangements.

References: PC duties [11N] and general duties [11J–11L] in legislation.gov.uk.

Competence and evidence the inspector will expect

• Everyone must have the right skills, knowledge, experience and behaviours. Trainees must be supervised. Organisations need organisational capability with a named ‘designated individual’. Source: SI 2023/911 Regulation 6.
• The PD and PC must be competent for their roles. Many firms use BSI PAS standards (e.g., PAS 8671 for PDs, PAS 8672 for PCs) to evidence competence. See the government’s explanatory materials and circular letter on the new building control regime: DLUHC circular.
• At completion or early occupation, the notice must include signed statements from the PD and PC confirming they fulfilled their duties, plus appointment details. Legal basis: Regulation 16.

Minor works carve-out

Part 2A dutyholder requirements do not apply where the work is only the very low‑risk ‘minor work’ listed in Schedule 4. The technical Parts still apply. Check your scope carefully before assuming the carve‑out. See the Building Regulations text and local authority summaries (for example Maldon and Uttlesford council pages).

Simple workflows that pass muster

• Appointment letter: one page naming the PD and PC, the project address, scope, start date and the designated individual (if an organisation). Keep it with your building control application.
• Design coordination notes: PD keeps a log of design decisions and who was consulted. Short weekly note is fine on small jobs.
• Site diary: PC keeps a daily or weekly record of who was on site, key checks, and any changes. Photos of concealed works help with the ‘Golden Thread’ of information.
• Completion pack: add the PD/PC signed statements, certificates, manuals and as‑builts.

For photo and evidence habits, see our guide to Interim valuation evidence packs and our Waste transfer note template.

Templates you can copy

• PD/PC appointment line to drop into your contract: “The Client appoints [Name/Company] as Principal Designer and [Name/Company] as Principal Contractor for the purposes of the Building Regulations 2010 Part 2A. Each confirms competence and a designated individual (if applicable). Appointments take effect from [date].”
• Completion statement reminder: “On completion/early occupation, the PD and PC will provide signed statements confirming compliance with their Part 2A duties, including appointment details, for submission to building control.”
• Evidence list for domestic extensions: appointments, competence checks, design coordination notes, site diary entries, concealed‑work photos, certificates (electrical, gas, fire‑stopping), O&M manuals.