Aptoris

Free CDM tool

Which CDM duty holders does my project need?

Answer two questions about the client and contractor structure to see which CDM 2015 roles apply and who carries the client duties.

Takes about 1 minute · No sign-up required

This checker assumes the work is a construction project under CDM 2015.Not sure?Check whether CDM applies first

Client type

Who is the construction work being carried out for?

This determines whether the client duties remain with a commercial client or are dealt with through the special domestic-client arrangements.

Choose an answer to continue.

When are a Principal Designer and Principal Contractor required?

For a project where more than one contractor is, or is reasonably foreseeable to be, working at any time, the client must appoint a Principal Designer and a Principal Contractor in writing. On a one-contractor project those principal appointments are not required solely by the project structure, although client, designer, contractor and worker duties can still apply. Regulation 5, CDM 2015: appointment of the Principal Designer and Principal Contractor, the written-appointment requirement and the consequence where a commercial client does not appoint (opens in a new tab)

The Principal Designer must be a designer with control over the pre-construction phase, and the Principal Contractor a contractor with control over the construction phase — never automatically the architect or the largest contractor. Both appointments must be made as soon as practicable and, in any event, before the construction phase begins. The trigger is the same on commercial and domestic projects; what differs is how the client duties are carried. Regulation 8, CDM 2015: skills, knowledge, experience and organisational capability (opens in a new tab)

What counts as more than one contractor under CDM?

A contractor is anyone who carries out, manages or controls construction work as part of a business — including companies, self-employed people and subcontractors. The test counts contractor organisations, not people on site. HSE: what do I need to do?: definitions of the CDM duty holders and an overview of each role (opens in a new tab)

  • One building company employing 25 workers is one contractor.
  • A main contractor plus an electrical subcontractor is more than one contractor.
  • A contractor who is reasonably foreseeable later in the programme counts from the start, not from the day they arrive.

Worker headcount never decides the trigger, and nor does project value, duration or whether the project is notifiable to HSE. The F10 Notification Calculator checks notification separately, and its answer does not change which duty-holder roles apply.

CDM duty holders at a glance

One line per role. The CDM duty holders guide sets out what each duty holder actually has to do.

The CDM 2015 duty holders and when each role applies
RoleWhen it applies
ClientEvery project has a client. Commercial and domestic client arrangements differ.
DesignerAnyone who prepares or modifies design as part of a business.
Principal DesignerProjects involving, or reasonably foreseeable to involve, more than one contractor.
Principal ContractorProjects involving, or reasonably foreseeable to involve, more than one contractor.
ContractorAnyone carrying out, managing or controlling construction work.
WorkerIndividuals carrying out construction work.

On a domestic project the specified client duties are carried by the contractor where there is only one contractor, by the Principal Contractor where there is more than one, or by the Principal Designer where the domestic client has made a written agreement to that effect. HSE: domestic clients: how the domestic client duties are carried by other duty holders (opens in a new tab)

One organisation may hold more than one role where it meets the requirements for each, without merging the duties. A construction phase plan is required on every construction project: prepared by the sole contractor where there is one, and by the Principal Contractor where there is more than one. HSE: summary of duties: duty-holder summary and the domestic-client arrangements (opens in a new tab)

Duty-holder checker FAQs

  • When is a Principal Designer required under CDM 2015?

    When more than one contractor is, or is reasonably foreseeable to be, involved. The client must appoint a designer with control over the pre-construction phase, in writing.

  • When is a Principal Contractor required?

    When more than one contractor is, or is reasonably foreseeable to be, involved. The client appoints a contractor with control over the construction phase, in writing.

  • Is a Principal Designer always required?

    No. Only on projects involving, or reasonably foreseeable to involve, more than one contractor. A genuine single-contractor project does not need the appointment, although designer duties still apply to anyone carrying out design work.

  • Does having many workers mean I need a Principal Designer and Principal Contractor?

    No. The trigger is more than one contractor, not the number of workers employed by one contractor. A single contractor with a large workforce is still one contractor.

  • Do CDM duties still apply on a one-contractor project?

    Yes. The absence of principal appointments does not remove the other CDM duties, and a construction phase plan is still required before construction begins.

  • Can one organisation hold more than one CDM role?

    Yes, provided it satisfies the requirements for each role and can carry out all of the relevant functions. Holding two roles does not merge or reduce either set of duties.

  • Are the CDM roles the same as the Building Regulations Principal Designer and Principal Contractor?

    No. The Building Regulations Principal Designer and Principal Contractor are separate legal appointments under different legislation. This checker covers the CDM 2015 roles only.

Checked against official CDM guidance

This checker applies the duty-holder rules in Regulations 5, 7 and 8 of the Construction (Design and Management) Regulations 2015, together with current HSE guidance. It is guidance based on the answers you select, not a compliance determination, and the sources below remain authoritative.

Last reviewed:

Read more on the CDM duty holders

This checker applies the project-structure rules. The guides explain what each role actually has to do.

  • Guide

    CDM duty holders explained

    The detailed guide behind this checker: who each duty holder is, what they must do, and how the roles fit together across a project.

  • Topic hub

    CDM Hub

    Plain-English CDM 2015 guidance, free tools, checklists and role-relevant training in one place.