Who does what during your build

A building project involves multiple professionals, legal duties and statutory approvals. Confusion about roles often leads to delays, duplicated responsibility or assumptions about “who was meant to do that?”

Clarity at the outset prevents problems later. The key roles are explained below.

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You - the Client

You are at the centre of the project.
Your responsibilities are to:

  • Appoint competent professionals
  • Provide clear decisions when required
  • Approve scope and budget

You are not expected to understand regulations or technical detail — that is what your appointed team manages on your behalf.

Principal Designer

Leads the design phase and oversees regulatory coordination. Responsibilities include:

  • Coordinating architect, engineer and consultants
  • Ensuring compliance with Building Regulations
  • Managing legal duties under CDM Regulations
  • Liaising with planning authorities and statutory bodies

The Principal Designer ensures the project is properly defined before construction begins.

Structural Engineer

Ensures the structure is safe and capable of performing as intended. Responsibilities include:

  • Designing beams, foundations and load-bearing elements
  • Producing structural calculations
  • Confirming load paths and structural integrity
  • Advising during construction if conditions change

They protect the physical performance of the building.

Principal Contractor

Principal Contractor (PC)
Manages the construction phase once work begins. Responsibilities include:

  • Coordinating all trades and subcontractors
    Managing health and safety on site
  • Sequencing works according to programme
  • Building in accordance with approved drawings
  • Coordinating inspections with Building Control

They are responsible for controlled delivery on site.

Building Control Officer

Independent authority ensuring compliance with Building Regulations. Responsibilities include:

  • Inspecting key construction stages
  • Confirming structural and fire compliance
  • Reviewing insulation, drainage and ventilation
  • Issuing the final Completion Certificate

They provide legal confirmation that work meets current standards.

Local Planning Authority

Assesses whether the proposal is acceptable in principle. Planning focuses on:

  • Appearance and scale
  • Neighbour impact
  • Street character
  • Policy compliance

Planning does not assess construction safety or structural design.

How They Work Together

You appoint the team, and each role has a defined responsibility.

  • The Principal Designer develops the proposal and secures planning approval.
  • After approval, the Structural Engineer develops the structural design and Building Regulations detail.
  • Only once the technical package is complete does the Principal Contractor take responsibility for delivery on site.

Clarity between them ensures your project progresses in a coordinated and legally compliant way.

In Summary:

You are at the centre. Around you, a structured professional team manages design, compliance and construction – allowing your project to move from concept to completion in a controlled, organised manner.