Principal Contractor Duties: What You're Actually Responsible For

What is a Principal Contractor under the BSA?

The Principal Contractor (PC) is the dutyholder responsible for planning, managing, monitoring and coordinating the construction phase of a building project. Under the Building Regulations (Amendment) (England) Regulations 2023 (SI 2023/911), the PC role is now a formal legal status — not just a project management description.

The PC role under the BSA sits alongside (and does not replace) the Principal Contractor role under the Construction (Design and Management) Regulations 2015 (CDM). On most projects, the same company will be PC under both regimes. The duties overlap but are not identical — the BSA adds building regulations compliance obligations on top of the health and safety obligations under CDM.

When does the PC role apply?

The PC role applies to notifiable building work in England (work that requires building regulations approval from a building control body) wherever the project involves more than one contractor, or where it is reasonably foreseeable that it will. If you are the only contractor on a project, the client is not required to appoint a Principal Contractor, though you may still hold other dutyholder responsibilities directly. Where more than one contractor is involved, this covers the vast majority of construction work undertaken by SME contractors, including:

• New residential builds of any size
• Extensions to existing buildings (structural extensions, loft conversions, garage conversions)
• Commercial new builds and fit-outs where building regulations apply
• Material changes of use (converting a house to flats, converting commercial to residential)
• Structural alterations
• Installation of regulated services (drainage, heating systems, certain electrical work)

Minor repairs, painting, and decorating that do not affect the structural integrity or regulated services of the building are generally not notifiable. If in doubt, check with your building control body before starting.

Your core duties as Principal Contractor

The Building Regulations set out the PC's duties in Regulations 11A–11D (as amended by SI 2023/911). The core obligations are:

What you cannot delegate

The PC role carries personal legal responsibility. There are specific things that cannot be passed to a subcontractor or sub-contracted away:

• The competence check obligation. You must check the competence of contractors you appoint directly. You cannot instruct a subcontractor to run their own competence checks and discharge your obligation. If a sub-subcontractor causes a compliance failure, your failure to check the appointing subcontractor's competence can expose you.
• The construction control plan. The plan must be prepared by or on behalf of the PC. It cannot be a document inherited from the client or the previous occupier of the site.
• Building control cooperation. Notices, inspections and compliance declarations must be submitted by or with the authority of the PC. Delegating this to a subcontractor without oversight creates a compliance gap.
• For HRBs: Gateway process. The PC must be named in the Gateway 2 application. They cannot be substituted mid-project without notifying the BSR. The PC is legally responsible for ensuring no work begins before Gateway 2 approval and that Gateway 3 documentation is complete.

Your relationship with the client

The client appoints the PC — the appointment must be in writing before construction begins. This is not a formality. It is a legal act that transfers the day-to-day construction phase duties from the client to the PC.

What the client retains, even after appointing a PC:

• The duty to ensure that the appointed PC is competent for the role
• The duty to ensure that there is always a PC in place — if the PC withdraws, the client must appoint a replacement immediately or the construction phase must pause
• The duty to ensure that the PC has the information they need to carry out their role (including design information from the principal designer)
• For HRBs: the duty to apply for Gateway 2 (this is the client's obligation, not the PC's, though in practice the PC usually prepares the application)

The practical implication: if a client is pressuring you to start work before your PC appointment is formalised in writing, or before a PD is appointed, you should refuse — or obtain written confirmation of both appointments before commencing. The liability exposure if something goes wrong without a properly constituted dutyholder structure falls primarily on the party who proceeded without one.

Your relationship with the Principal Designer

The Principal Designer (PD) is responsible for coordinating the design phase and ensuring the design information needed for safe construction is produced and communicated to the PC. The PC and PD must cooperate — this is a legal obligation on both sides.

In practice, the PC's interface with the PD typically involves:

• Receiving design information before and during construction — including changes to design that affect the construction approach
• Providing feedback to the PD on buildability issues that may require design revision
• Notifying the PD of changes made during construction that differ from the approved design
• For HRBs: coordinating on golden thread information — what the PC records during construction, and what the PD needs for the overall handover package
• At completion: contributing the health and safety file information to the PD for collation and handover

On smaller SME projects, the same person sometimes fulfils both PC and PD roles — particularly where there is no separate architect and the builder is designing as well as building. This is permissible, but the obligations of both roles still apply and must be fulfilled by the same person.

Your own competence as PC

The PC itself must be competent for the PC role. This means the company (or individual, if you are a sole trader) must have the skills, knowledge, experience and organisational capability appropriate to the role of principal contractor on the specific project being undertaken.

You do not need a formal accreditation to be a PC. But you do need to be able to demonstrate competence if challenged. This is an area where being able to point to:

• Relevant trade body membership (Federation of Master Builders, CIBSE, CIOB, RICS etc.)
• Similar projects completed successfully
• A clear system for managing compliance (documentation, subcontractor checking, building control coordination)
• Staff with relevant qualifications and CSCS cards

... all strengthen your position. The BSR and building control authorities are increasingly looking at whether the PC has a credible compliance management system — not just a formal qualification.

Enforcement: what happens if you get it wrong

Failure to comply with the Building Regulations as PC can result in:

• Criminal prosecution — under Section 35 of the Building Act 1984 (as amended by the BSA). Fines are unlimited. On conviction, directors and senior managers can be personally liable.
• Stop notices — the building control body or BSR can issue a stop notice halting all construction work until compliance is demonstrated. On a live site, this is commercially devastating.
• Enforcement notices — requiring you to pull down and rebuild non-compliant work. The cost of non-compliant work is borne by the PC, not the building control authority.
• Civil liability — if a subcontractor causes injury and you cannot demonstrate you checked their competence before appointment, your exposure in negligence claims increases significantly.
• For HRBs: Gateway refusal — Gateway 3 refusal means the building cannot be occupied. The cost of rectification — and any losses incurred by the client while the building is vacant — may fall on the PC if the non-compliance is attributable to their failure.

How Subchecked supports your PC obligations

The obligation to check subcontractor competence before appointment is one of the clearest and most consistently enforceable of the PC's duties. It is also one of the easiest to fail on — not because contractors don't care, but because informal checks (looking at a card, taking someone's word for their CIS registration) leave no record and constitute no demonstrable due diligence.

Subchecked handles the objective, register-verifiable competence checks for every subcontractor:

• CSCS cards — verified against the CITB live register. Card type, trade, and expiry date recorded. A photo of a card is not sufficient — you need confirmation it is genuine and current.
• CIS registration status — verified via HMRC Government Gateway. Confirms whether the subcontractor is registered and what deduction rate applies. Required before first payment under CIS.
• Right to Work — document capture and verification with timestamp. A required pre-appointment check under the Immigration Act 2014.
• Insurance — insurer-confirmed cover or document-level verification, with the verification level explicitly recorded so the compliance pack is transparent about what was achieved.
• Trade-specific checks — Gas Safe verification for gas trades; NICEIC/NAPIT for electrical trades.

Every check is timestamped and exportable. The result is a compliance pack for each subcontractor that shows, clearly and specifically, what was checked, when, and what the result was. This is the record you need if the BSR, a building control officer, or a solicitor asks you to demonstrate that you took reasonable steps.