CDM 2015 Explained: What Every UK Contractor Needs to Know
CDM 2015 — the Construction (Design and Management) Regulations 2015 — is the primary piece of legislation governing health and safety management on UK construction projects. It applies to virtually every construction project in the country, sets out who is responsible for what, and underpins almost every H&S document a UK contractor is ever asked to produce.
Yet for smaller contractors and subcontractors, CDM can feel opaque. The duty holder terminology is confusing. The boundaries of who needs to do what are not always clear. And the consequences of getting it wrong — enforcement action, prosecution, unlimited fines — are significant enough that it is worth understanding properly.
This guide explains CDM 2015 in plain English: what it requires, who it applies to, and what it means in practice for the contractors who work under it every day.
What is CDM 2015?
The Construction (Design and Management) Regulations 2015 replaced CDM 2007 and came into force on 6 April 2015. They are the legal framework through which health and safety in construction is planned, managed, and coordinated from a project's earliest stages through to completion.
CDM 2015 is based on a simple principle: that health and safety outcomes on construction projects are determined largely by decisions made early — at design stage, during procurement, and in the planning of construction work — not just by what happens on site. A building designed with safe maintenance access built in, a project with adequate time and money budgeted for safe working, a construction phase plan prepared before work starts: these are the things that prevent injuries and deaths.
CDM 2015 places duties on everyone involved in a project — clients, designers, and contractors — and allocates specific responsibilities to named duty holders depending on the scale and nature of the project.
The three duty holder roles
The Client
The client is the organisation or individual for whom the construction project is carried out. This can be a company commissioning new premises, a housing developer, a local authority, or a homeowner having an extension built.
Under CDM 2015, clients have specific duties regardless of how hands-off they intend to be. They must:
- Make suitable arrangements for managing the project, including allocating sufficient time and resources
- Ensure that the principal designer and principal contractor are appointed in writing where required
- Ensure a pre-construction information pack is prepared and provided to designers and contractors
- Ensure a construction phase plan is prepared before the construction phase begins
- Ensure a health and safety file is prepared and handed over on project completion
Domestic clients (homeowners commissioning work on their own home) have most of these duties transferred to the principal contractor or principal designer by default — but the duties still exist and must be discharged by someone.
The Principal Designer
The principal designer is appointed by the client on projects involving more than one contractor. They are responsible for planning, managing, monitoring, and coordinating health and safety in the pre-construction phase.
In practice, this means identifying and managing design risks: ensuring that the design does not create unnecessary hazards during construction, maintenance, or eventual demolition. The principal designer must have the skills, knowledge, and experience necessary to carry out this function — it is not automatically the lead architect or the largest design firm.
The Principal Contractor
The principal contractor is appointed by the client to plan, manage, monitor, and coordinate the construction phase. On any project involving more than one contractor, a principal contractor must be appointed in writing before the construction phase begins.
The principal contractor's duties include:
- Preparing and maintaining the construction phase plan
- Organising cooperation between contractors
- Ensuring that all workers on site receive a suitable site induction
- Ensuring that the construction phase plan is followed and updated as the project develops
- Displaying the project notification (F10) on site where required
- Liaising with the principal designer on H&S matters
For smaller contractors who operate as principal contractors on their own projects — managing subcontractors beneath them — this role carries significant legal weight. The principal contractor is accountable for the H&S management of the whole construction phase, not just their own direct work.
When does CDM 2015 apply?
CDM 2015 applies to all construction work in Great Britain. There is no minimum project size or value that exempts a project from the regulations.
However, certain additional duties — specifically the requirement to appoint a principal designer, notify the HSE (F10 notification), and manage the health and safety file — only apply to projects that are notifiable.
A project is notifiable if the construction phase will either:
- Last longer than 30 working days with more than 20 workers simultaneously on site at any point, or
- Exceed 500 person-days of construction work
For smaller domestic projects and short-duration commercial works, the F10 notification and the formal principal designer appointment may not apply. But the core duties — risk assessment, method statements, adequate resources, a construction phase plan — apply to all projects involving more than one contractor.
If you are the only contractor on a project, you are not required to have a principal contractor or principal designer. But you still need to plan and manage the work safely, and you still need to produce compliant risk assessments for your scope.
What documents does CDM 2015 require?
The specific documents required under CDM 2015 depend on the project type and your role, but the following are the core deliverables:
Pre-construction information — prepared by the client and principal designer, this covers existing information about the site: hazards, existing services, previous uses, asbestos surveys, and structural drawings. You should receive this before you price or plan your work.
Construction phase plan — prepared by the principal contractor before work starts and updated throughout the project. This is the live safety management document for the construction phase: how the site will be managed, the risks identified and controlled, the welfare arrangements, and the emergency procedures.
Risk assessments and method statements (RAMS) — required for every contractor's scope of work. As a subcontractor, you are responsible for producing RAMS for your activities and providing them to the principal contractor for review and approval before work starts.
Site induction records — every worker on a CDM project must receive a site induction. Records of who has been inducted, when, and on what topics must be kept.
Health and safety file — prepared by the principal designer and handed to the client on project completion. Contains information relevant to future maintenance, alteration, and demolition of the structure. As a subcontractor, you may be required to contribute information — equipment schedules, installation records, O&M manuals — to the H&S file.
The most common CDM mistakes small contractors make
Not appointing a principal contractor in writing — on a project with two or more contractors, the principal contractor must be formally appointed. Assuming one party is in charge without a written appointment is a common and significant compliance failure.
Starting on site without a construction phase plan — the construction phase must not begin until a construction phase plan is in place. A brief, functional plan prepared the day before the project starts is legal. No plan at all is not.
Generic RAMS submitted without review — subcontractors who submit identical, clearly generic RAMS for every project are not meeting their CDM duty. Principal contractors who accept them without review are not meeting theirs.
Ignoring domestic project duties — CDM 2015 applies to domestic projects. Many smaller contractors working on residential extensions, loft conversions, and refurbishments either do not know this or choose to ignore it. The duty to plan, manage, and assess risk does not disappear because the client is a homeowner.
No H&S file at the end of the project — on notifiable projects, the health and safety file must be handed to the client on completion. Failing to produce one — and more commonly, failing to gather contributions from subcontractors throughout the project — is a widespread compliance failure.
CDM documents and templates
Every document required under CDM 2015 for your scope of work as a subcontractor — RAMS, permits to work, risk assessments, method statements, sub-contractor review forms — is available in the SafetyPod library.
→ Sub-Contractor RAMS Review Form — for principal contractors reviewing subcontractor submissions
Written by the SafetyPod team — NEBOSH-qualified H&S professionals with hands-on experience across UK construction, civil engineering, and facilities management. All content is written to current HSE guidance and CDM 2015 compliance.
Last reviewed: June 2026