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The Construction (Design and Management) Regulations 2015, known as CDM 2015, are the main set of regulations for managing health, safety and welfare on construction projects in Great Britain. They came into force on 6 April 2015, replaced CDM 2007, and apply to every construction project, from a kitchen refit to a new hospital.
CDM works by giving clear duties to the people who can most influence safety: the client who pays for the work, the designers who shape it and the contractors who build it. This guide sets out every duty holder, links to a full guide on each, and explains the key documents.
What counts as construction work?
The definition is wide. It includes building, altering, converting, fitting out, commissioning, renovating, repairing, maintaining, redecorating, decommissioning, demolishing and dismantling a structure. It also covers site clearance and investigation, assembling prefabricated elements on site, removing structures and waste, and installing, maintaining or removing fixed services such as electrical, gas, plumbing and telecoms. Some cleaning counts too, for example high pressure water or abrasive cleaning.
If you are unsure whether your work is covered, assume it is. Most building, maintenance and refurbishment work falls within CDM.
The duty holders at a glance
| Duty holder | Who they are | Main duties | Full guide |
|---|---|---|---|
| Client | The person or organisation the project is carried out for | Make suitable arrangements, allow enough time and resources, provide pre-construction information, appoint the principal designer and principal contractor | Client duties |
| Domestic client | A householder having work done on their own home, not for business | Duties pass automatically to the contractor, principal contractor or principal designer | Client duties |
| Principal designer | A designer appointed by the client where there is more than one contractor | Plan, manage, monitor and coordinate health and safety in the pre-construction phase, prepare the health and safety file | Principal designer duties |
| Designer | Anyone who prepares or modifies a design, or arranges or instructs someone else to | Eliminate, reduce or control foreseeable risks through design and pass on information | Designer duties |
| Principal contractor | A contractor appointed by the client where there is more than one contractor | Plan, manage, monitor and coordinate the construction phase, draw up the construction phase plan, provide welfare | Principal contractor duties |
| Contractor | Anyone who carries out, manages or controls construction work, including the self-employed | Plan, manage and monitor their own work, supervise and inform workers, follow the principal contractor’s directions | Contractor duties |
| Worker | Anyone working on the project under the control of a contractor | Cooperate, report anything likely to endanger anyone, only do work they are competent for | Worker duties |
When are a principal designer and principal contractor needed?
Whenever there is, or is likely to be, more than one contractor on a project, the client must appoint a principal designer and a principal contractor in writing, as early as possible. If the client does not, the client must carry out those duties itself. On a single contractor project neither appointment is needed, but the contractor must still draw up a construction phase plan.
Notifying HSE
A project must be notified to HSE if the construction work will last more than 30 working days with more than 20 workers working at the same time at any point, or will exceed 500 person days. Notification is the client’s duty and is made online using form F10. Being notifiable does not add extra duties beyond displaying the notice on site. Our F10 notification guide explains how it works.
The key documents
| Document | Who is responsible | When | Full guide |
|---|---|---|---|
| Pre-construction information | Client, with help from the principal designer | As early as possible, to every designer and contractor | Pre-construction information |
| Construction phase plan | Principal contractor, or the only contractor | Before the construction phase begins, kept up to date | Construction phase plan |
| Health and safety file | Principal designer, then the principal contractor | Built during the project, handed to the client at the end | Health and safety file |
| F10 notification | Client | Before the construction phase, for notifiable projects | F10 notification |
How the regulations are organised
| Part | What it covers |
|---|---|
| Part 1 | Commencement, interpretation and where the regulations apply |
| Part 2 | Client duties, appointments, notification and domestic clients |
| Part 3 | Duties of designers, principal designers, principal contractors and contractors, plus the plan and the file |
| Part 4 | General requirements for all construction sites, from safe places of work and excavations to traffic routes, fire and lighting |
| Part 5 | General provisions |
| Schedules | Notification particulars, minimum welfare facilities, high risk work needing specific measures, and more |
Duties that apply to everyone
- Competence. Anyone appointed as a designer or contractor must have the skills, knowledge and experience for the job, and organisations must have the organisational capability. Nobody should accept an appointment they cannot fulfil.
- Cooperation. Everyone with a duty must cooperate with anyone else working on or near the project.
- Reporting. Anyone working under someone else’s control must report anything likely to endanger themselves or others.
- Clear information. Any information or instruction given must be easy to understand.
The general principles of prevention
CDM expects duty holders to apply the general principles of prevention, set out in the Management of Health and Safety at Work Regulations 1999. In short: avoid risks, evaluate the risks that cannot be avoided, tackle risks at source, adapt work to the individual, use technical progress, replace the dangerous with the less dangerous, develop a coherent prevention policy, give collective measures priority over individual ones, and give workers proper instructions. Our guide to the hierarchy of controls shows how this works in practice.
CDM and the Building Regulations dutyholder roles
Since 1 October 2023, the Building Regulations in England also use the titles principal designer and principal contractor. Those roles are about compliance with building regulations, such as fire safety and structure. The CDM roles are about health and safety while the work is designed and built. They are separate duties, though the same organisation is often appointed to both. Our principal designer guide explains the difference.
Northern Ireland
CDM 2015 applies in England, Scotland and Wales. Northern Ireland has its own equivalent, the Construction (Design and Management) Regulations (Northern Ireland) 2016, which follows the same approach.
Training that helps
For a quick online introduction for anyone involved in projects, our CDM awareness eLearning covers the regulations and duty holders. Site managers usually need SMSTS and supervisors SSSTS. For directors and clients, the CITB Directors’ Role for Health and Safety course covers leadership duties, and the NEBOSH Health and Safety Management for Construction certificate covers CDM in depth for managers.
Where this fits in SMSTS and SSSTS
CDM duty holders, notification and the key documents are tested on both courses, especially SMSTS. Our free SMSTS mock test and SSSTS mock test let you check your knowledge before the course or a refresher, and you can email yourself the results sheet at the end.
When you are ready, the five day SMSTS course is for site managers and the two day SSSTS course is for supervisors. If your certificate is due, the SMSTS refresher and SSSTS refresher keep it current.
Frequently asked questions
What does CDM stand for?
Construction (Design and Management). The current regulations are the Construction (Design and Management) Regulations 2015.
Does CDM apply to small projects?
Yes. CDM 2015 applies to all construction projects, whatever their size or length, including work for domestic clients. The level of planning and paperwork should be in proportion to the risks.
Who are the duty holders under CDM 2015?
The client, principal designer, designers, principal contractor, contractors and workers. Domestic clients have their duties passed to others.
When must HSE be notified?
When the construction work will last more than 30 working days with more than 20 workers at the same time at any point, or will exceed 500 person days.
Who enforces CDM 2015?
HSE enforces CDM on construction sites in Great Britain. Its guidance L153 explains how to comply.
Read the source
The Construction (Design and Management) Regulations 2015 (SI 2015/51), including regulations 2 to 15 and Schedules 1 to 3; HSE guidance L153, Managing health and safety in construction; the Management of Health and Safety at Work Regulations 1999, Schedule 1; the Building Regulations etc. (Amendment) (England) Regulations 2023; and the Construction (Design and Management) Regulations (Northern Ireland) 2016. Facts checked on 6 October 2026.
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