The Construction (Design and Management) Regulations 2015 — known as CDM 2015 — set out legal duties for managing health, safety and welfare on UK construction projects. They apply to all construction work, from a single tradesperson fitting a kitchen to a multi-million-pound infrastructure project. CDM 2015 defines five duty holders: client, principal designer, designer, principal contractor and contractor — each with specific responsibilities. Projects involving more than one contractor require a written construction phase plan. Notifiable projects (over 30 days with more than 20 workers, or more than 500 person-days) must be notified to HSE before work starts. Failure to comply is a criminal offence under the Health and Safety at Work etc. Act 1974.
CDM 2015 catches more people than expected. It applies to domestic clients, small builders, and one-person trades — not just major contractors. Many people who fall under the regulations don't realise they have legal duties at all until something goes wrong.
This guide covers what CDM is, who it applies to, what each duty holder has to do, the documents that need to exist on a project, and the common mistakes that catch employers and contractors out. It's written for site managers, contractors, designers, clients and anyone planning construction work who needs a clear picture of their CDM duties.
CDM stands for the Construction (Design and Management) Regulations 2015. They're a UK statutory instrument that applies to all construction work in Great Britain. Northern Ireland has equivalent legislation administered separately.
The 2015 version replaced the 2007 regulations and significantly broadened the scope — particularly bringing domestic clients (homeowners commissioning work) within the regulatory framework for the first time.
CDM applies to all construction work in Great Britain. The definition of construction work is broad and includes:
"Maintenance" is where CDM catches people out — repointing, gutter clearance, window cleaning at height, and similar work all fall within scope.
A project is "notifiable" — meaning HSE must be told before construction starts — if either:
Notification is made via HSE's online F10 form. Notification doesn't change the duties — projects still need a construction phase plan and the same duty holders — but failure to notify when required is a separate offence.
CDM 2015 defines five duty holders, each with specific responsibilities:
| Duty holder | Who they are | Key responsibility |
|---|---|---|
| Client | The person or organisation for whom the work is being carried out | Make suitable arrangements for the project; ensure other duty holders are appointed in good time |
| Principal Designer | The designer in charge of the pre-construction phase (only required where more than one contractor is involved) | Plan, manage and monitor the pre-construction phase; coordinate health and safety in design |
| Designer | Anyone preparing or modifying designs (architects, engineers, drainage designers, etc.) | Eliminate, reduce or control foreseeable risks through design choices |
| Principal Contractor | The contractor in charge of the construction phase (only required where more than one contractor is involved) | Plan, manage and monitor the construction phase; produce the construction phase plan |
| Contractor | Anyone managing or carrying out construction work | Plan, manage and monitor their own work; comply with directions from the principal contractor |
One person or organisation can hold multiple duty-holder roles. A small builder doing a domestic kitchen fit-out might be designer, principal designer, principal contractor and contractor simultaneously. The duties don't disappear — they all apply to the same person.
Clients carry significant responsibilities under CDM 2015 — more than most realise:
Homeowners commissioning construction work for their own home are "domestic clients." Their duties pass automatically to:
So a domestic client's duties don't disappear — they're transferred to the contractor or principal contractor by default. Many small builders take on these duties without realising it.
The Principal Designer (PD) leads health and safety in the pre-construction phase. They must:
The PD must have the skills, knowledge, experience and (if an organisation) organisational capability to perform the role. They're typically the lead designer on the project — the architect on a building project, the lead engineer on civil engineering works.
"Designer" under CDM 2015 includes anyone preparing or modifying designs — not just architects. The definition catches:
Designers must eliminate, reduce or control foreseeable risks through their design choices — applying the principle of "design out hazards where reasonably practicable." If risks cannot be eliminated through design, designers must provide information enabling others to manage what's left.
The Principal Contractor (PC) leads health and safety in the construction phase. They must:
Contractors — anyone carrying out or managing construction work — must:
This applies whether they're a contractor or sub-contractor, employer or self-employed. Even a one-person trade has these duties on every job they do.
CDM 2015 expects three key documents to flow through the project lifecycle:
Provided by the client (typically through the principal designer) to designers and contractors. Includes information about:
Produced by the principal contractor (or sole contractor on single-contractor projects) before construction starts. Sets out how the construction phase will be managed, including:
The CPP must be in place before construction starts. For domestic projects, the CPP is often a simple proportionate document — but it still has to exist.
Compiled during the project and handed to the client at completion. Contains information about the building or structure that future owners, occupiers, designers and contractors will need to manage health and safety risks during use, maintenance, refurbishment, demolition, etc.
Common contents include "as-built" drawings, structural details, hazardous materials registers, and design assumptions.
CDM applies to all construction work, regardless of size. The level of documentation can be proportionate — but the duties exist on every project.
Wrong. Domestic clients' duties pass to the contractor or principal contractor automatically. Small builders typically end up holding extra duties they didn't know about.
The principal designer is required on any project with more than one contractor, regardless of how many designers there are. The trigger is the construction phase — not the design team.
No. The CPP must be in place before construction starts. HSE inspections check this routinely.
Some maintenance work does fall within CDM — particularly anything involving working at height, hazardous substances, or significant risk. Window cleaning at height, gutter clearance, and roof inspections can all engage CDM duties depending on the work.
Notification is administrative. The substantive duties — appointment of duty holders, production of the CPP, coordination of designers and contractors — still apply and aren't satisfied by the F10 form alone.
CDM 2015 requires duty holders to have (or appoint people with) the skills, knowledge, experience and — for organisations — organisational capability to discharge their duties. There's no set qualification, but in practice:
Yes. CDM 2015 applies to all construction work regardless of size. The level of documentation and formality can be proportionate to the project, but the underlying duties apply on every job.
Yes. Homeowners are "domestic clients" under CDM 2015. Their duties pass automatically to the contractor (single-contractor project) or principal contractor (multi-contractor project) by default — but the duties exist nonetheless.
The client. Notification is via the F10 online form on the HSE website, and must be done before construction starts on notifiable projects. The principal contractor must display the F10 notification on site.
All designers have CDM duties to eliminate or control risks through design. The Principal Designer is appointed on multi-contractor projects to coordinate health and safety across all designers in the pre-construction phase. The PD is typically the lead designer on the project.
On any project where more than one contractor is or will be working — regardless of project size. Even a small domestic project with two trades requires both a principal designer and principal contractor.
Failure to comply is a criminal offence under the Health and Safety at Work etc. Act 1974. Penalties include unlimited fines and, for serious cases, imprisonment for up to two years. Enforcement notices, prohibition notices, and improvement notices are more common day-to-day responses.
The file should be kept for the lifetime of the building or structure. Each subsequent client (when the building is sold or transferred) should receive the file and keep it for use during future maintenance, refurbishment or demolition.
If you're a site manager, supervisor or contractor working on UK construction, the qualification that fits CDM-relevant duties is the NEBOSH National Construction Certificate. It covers CDM 2015 in detail alongside the broader hazard set you'll encounter on construction sites.
For directors or senior leaders carrying client duties, IOSH Leading Safely covers the strategic-level safety and CDM client duties at director level.
KeyOstas is a NEBOSH Gold Learning Partner with 41 years' experience delivering construction safety training. Call us on +44 (0) 3300 569534 for advice on the right CDM-related training for your team or project.
