The Construction (Design and Management) Regulations 2015 (CDM 2015) are the main regulations governing how health, safety and welfare are managed on construction projects in Great Britain. They apply to all construction projects, whatever their size, and place legal duties on clients, designers, contractors, the Principal Designer and the Principal Contractor.

If you are commissioning a commercial project, CDM 2015 matters to you directly. The client sets the budget, the programme and the appointments, and the regulations hold the client accountable for those decisions. This guide explains what CDM 2015 is, when it applies, what you must do as a client, when a project has to be notified to the Health and Safety Executive (HSE) and which documents you should expect to see. If you would like support on a project, our CDM Services cover client advice and Principal Designer appointments.

KEY POINTS

CDM 2015 applies to all construction work in Great Britain, from a small fit-out to a new build. Northern Ireland has its own equivalent regulations.
A commercial client’s duties start as soon as the project begins, and they stay with the client even when advisers are appointed.
If more than one contractor will work on the project, the client must appoint a Principal Designer and a Principal Contractor in writing.
A project must be notified to HSE if it will last more than 30 working days with more than 20 workers on site at once, or exceed 500 person days.
Three documents run through the project: pre-construction information, the construction phase plan and, where there is more than one contractor, the health and safety file.

What Are the CDM Regulations 2015?

CDM stands for Construction (Design and Management). The regulations are a statutory instrument (SI 2015/51) made under the Health and Safety at Work etc. Act 1974. They came into force on 6 April 2015, replacing the CDM Regulations 2007. You can read the full text of CDM 2015 on legislation.gov.uk, and HSE publishes free official guidance, L153 Managing health and safety in construction.

The thinking behind CDM is simple: many of the risks on a construction project are decided long before anyone arrives on site. The design, the programme, the budget and the people appointed all shape how safely a building can be built, used, cleaned and maintained. CDM 2015 makes sure health and safety is planned in from the start and coordinated throughout, rather than left to the contractor once work begins. HSE describes the aim as a project that is safe to build, use and maintain while still offering good value.

In practice, CDM 2015 does three things:

It gives every party a defined role. Clients, designers, contractors, the Principal Designer, the Principal Contractor and workers each have duties, known as duty holder duties.
It requires those duties to be planned and coordinated across the design and construction phases, so information reaches the people who need it.
It sets minimum standards for every construction site, from site security and excavations to traffic routes, fire precautions and welfare facilities.

For a commercial client, the most important point is timing. Decisions about access, future maintenance, how work is phased in an occupied office or a trading store, and how much time the works are given all carry health and safety consequences. They are far easier to get right at the briefing and design stages than once a contractor is on site.

Does CDM 2015 Apply to Your Project?

If the work is in Great Britain, almost certainly. CDM 2015 has no minimum size, value or duration. Size only affects whether the project must be notified to HSE. Whether you need a Principal Designer and a Principal Contractor depends on the number of contractors, not the size of the project.

Office fit-outs and refurbishments are construction work under CDM 2015.

“Construction work” is defined broadly in the regulations. It includes:

Building new structures, and altering, converting, fitting out, renovating, repairing, maintaining or redecorating existing ones
Demolition and dismantling
Site clearance, investigation, excavation and preparation
Installing, commissioning, maintaining or removing mechanical, electrical, gas, telecommunications, computer and similar services that are fixed within or to a structure

So an office fit-out, a store refurbishment and an electric vehicle (EV) charging installation involving groundworks and new electrical supplies are all construction work under CDM 2015.

Are you a commercial or a domestic client?

You are a commercial client if the work is done in connection with a business, whether or not that business makes a profit. HSE confirms this includes local authorities, housing associations and landlords who own domestic property. A domestic client is someone having work done on their own home, or a family member’s, that is not connected with a business. A domestic client’s duties pass to the contractor, to the Principal Contractor where there is more than one contractor, or to the Principal Designer if they agree this in writing. This guide is written for commercial clients.

What about Northern Ireland?

CDM 2015 covers England, Scotland and Wales. Projects in Northern Ireland come under the Construction (Design and Management) Regulations (Northern Ireland) 2016, which follow a very similar structure.

What Are the Client’s Duties Under CDM 2015?

HSE points out that the commercial client has a major influence on how a project is procured and managed. The client controls the contracts, appoints the designers and contractors, and decides the money, time and other resources available, so CDM 2015 makes the client accountable for the effect of those decisions on health, safety and welfare.

Your duties begin as soon as the decision is made to go ahead and early planning and design work starts. They continue after construction ends, for as long as you keep an interest in the building. You do not need to be a construction expert, but you must make suitable arrangements for the project and appoint people who have the right expertise.

Client duty	What it means in practice
Make suitable arrangements for managing the project	Decide who does what, how information will flow and how health and safety will be managed. Allow sufficient time and other resources, and keep the arrangements under review throughout the project.
Appoint the right people	Take reasonable steps to check that designers and contractors have the skills, knowledge and experience, and, for organisations, the organisational capability, to carry out their role safely.
Appoint a Principal Designer and Principal Contractor	In writing, where more than one contractor will work on the project (see the next section).
Provide pre-construction information	As soon as practicable, to every designer and contractor appointed or being considered for appointment.
Make sure there is a construction phase plan	Before the construction phase begins, drawn up by the Principal Contractor, or by the contractor where there is only one.
Make sure there is a health and safety file	Where there is more than one contractor, prepared and kept up to date by the Principal Designer, kept available for anyone who needs it, and passed on if you sell your interest in the building.
Make sure welfare facilities are provided	Toilets, washing facilities, drinking water, rest areas and, where needed, changing facilities for everyone carrying out construction work.
Check that the Principal Designer and Principal Contractor are doing their jobs	Take reasonable steps to make sure they carry out their duties under the regulations.
Notify HSE if the project is notifiable	Before the construction phase begins (see below).

Checking competence is part of choosing your project team, not an extra step afterwards. Our guide to construction procurement explains how this fits into tender evaluation.

Can a client hand these duties to someone else?

A commercial client can appoint advisers, a project manager or a CDM consultant to help, but the legal duties stay with the client. Where there is more than one client, for example a landlord and a tenant on a fit-out, the clients can agree in writing that one of them will be treated as the only client. Every client must still cooperate with the project team and share relevant information they hold.

Time is a duty in its own right. An unrealistic programme is a CDM issue as well as a commercial one, and the HSE notification form even asks how much time the client has allowed for the construction work.

When Do You Need a Principal Designer and a Principal Contractor?

Where there is more than one contractor, or it is reasonably foreseeable that more than one contractor will work on the project at any time, the client must appoint in writing:

a Principal Designer: a designer with control over the pre-construction phase, to plan, manage, monitor and coordinate health and safety while the project is being designed and prepared
a Principal Contractor: a contractor to plan, manage, monitor and coordinate health and safety during the construction phase

Both appointments must be made as soon as practicable, and in any event before the construction phase begins. The Principal Designer adds most value while the design can still change, so the best time to appoint is while the brief and concept design are being developed. Our guide to the RIBA stages explains where that falls in a typical project.

More than one contractor is common, even on modest projects. A store refit with a shopfitter and a separate electrical contractor, or an EV project with a groundworks firm and a specialist charger installer, already has two contractors.

What if the client does not appoint them?

If the client fails to appoint a Principal Designer, the client must carry out the Principal Designer’s duties itself. The same applies to the Principal Contractor. For most commercial clients without in-house construction health and safety expertise, that is a significant legal responsibility to take on by default.

What if there is only one contractor?

With a single contractor, you do not need to appoint a Principal Designer or Principal Contractor. The contractor must draw up a construction phase plan before setting up the site, and a health and safety file is not required. Your other client duties, such as allowing enough time and resources and providing pre-construction information, still apply.

Who are the CDM duty holders?

Duty holder	Main focus
Client	Arrangements, appointments, time and resources, and information
Designer	Eliminating, reducing or controlling foreseeable risks through the design, and providing information about remaining risks
Principal Designer	Planning, managing, monitoring and coordinating health and safety in the pre-construction phase, and preparing the health and safety file
Principal Contractor	Planning, managing, monitoring and coordinating the construction phase, the construction phase plan, site inductions, site security and welfare
Contractor	Planning, managing and monitoring their own work, supervising and informing their workers, and making sure they have the right skills and training
Worker	Cooperating with others and reporting anything likely to endanger themselves or others

We look at each of these roles in more detail in our guide to CDM duty holders. [Editor: add the link to the CDM duty holders article when it is live]

GOOD TO KNOW
Not the same as the Building Regulations roles
Since 1 October 2023, the Building Regulations in England have their own Principal Designer and Principal Contractor roles. These are responsible for compliance with the Building Regulations rather than health and safety, so the names are the same but the duties are different. A client can appoint them separately, or certify in writing that its CDM Principal Designer and Principal Contractor are treated as appointed for Building Regulations purposes too.

Does Your Project Need to Be Notified to HSE?

A project is notifiable if the construction work on site is scheduled to:

last longer than 30 working days and have more than 20 workers working at the same time at any point, or
exceed 500 person days

A working day is any day on which construction work takes place, so weekends and bank holidays count if work is planned on them. Person days are the total number of days worked by everyone on the project. For example, a fit-out with an average of eight people on site over 70 working days adds up to 560 person days, so it is notifiable even though there are never more than 20 people on site at once.

On a notifiable project, HSE must be notified before the construction phase begins, and the notice displayed on site.

Who notifies, and how?

A commercial client must notify HSE in writing as soon as practicable before the construction phase begins, using HSE’s online F10 form. HSE no longer accepts paper forms or notifications by email or post. You can ask someone else, such as your Principal Designer or Principal Contractor, to submit the form for you, but the legal duty to notify remains yours. The form asks for contact details for the client, the Principal Designer and the Principal Contractor, the site address, a description of the work, the planned start date and duration, the time you have allowed for the construction work, the expected number of people and contractors on site, and a declaration that you are aware of your client duties.

The notice must be displayed in the construction site office where workers can read it, and updated if details change. Where the Office of Rail and Road is the enforcing authority for the work, the notice goes to it instead of HSE, and work on nuclear, authorised defence or new nuclear build sites is notified to the Office for Nuclear Regulation.

Notification does not decide whether CDM applies

A project below the notification thresholds still carries every other duty in the regulations. Assuming otherwise is a common misunderstanding carried over from CDM 2007, when notification decided whether certain appointments had to be made. Under CDM 2015, the number of contractors decides whether you need a Principal Designer and Principal Contractor, not the size of the project.

What Are the Key Documents Under CDM 2015?

Document	Who is responsible	When	What it is for
Pre-construction information	The client provides it; the Principal Designer helps gather and share it	As soon as practicable, to every designer and contractor appointed or being considered	Information about the project, its planning and management, and known hazards, such as asbestos surveys, existing drawings, details of services and site constraints, plus any existing health and safety file
Construction phase plan	The Principal Contractor, or the contractor where there is only one; the client makes sure it is in place	Before the site is set up, then reviewed and updated throughout the works	The health and safety arrangements and site rules for the construction phase, including specific measures for higher-risk work
Health and safety file	The Principal Designer prepares and updates it; the Principal Contractor takes it over if the Principal Designer’s appointment ends early	Needed where there is more than one contractor; started during the pre-construction phase and handed to the client at the end of the project	Information needed to carry out future construction work, maintenance, cleaning, alteration or demolition safely

These documents should be proportionate. Pre-construction information, for example, must be relevant to the work and at a level of detail that matches the risks involved. A short, accurate document that the team actually uses is worth more than a long generic one.

What Happens If CDM 2015 Is Not Followed?

CDM 2015 is criminal law made under the Health and Safety at Work etc. Act 1974. HSE inspects construction sites and can take enforcement action, including improvement notices, prohibition notices that can stop work, and prosecution. Weak CDM arrangements also tend to surface late, as redesign, delays and people put at risk, when they cost the most to fix.

Common CDM Mistakes Clients Make

Appointing the Principal Designer late, after the design is largely fixed and there is little left to influence.
Assuming the contractor handles CDM, when the client’s duties start before any contractor is appointed.
Setting an unrealistic programme that leaves too little time for design, procurement or the works themselves.
Holding back information such as asbestos surveys, drawings or knowledge of the building.
Forgetting the occupied building: a store that keeps trading or an office that stays open brings risks to staff and customers that need planning from the start.
Losing the health and safety file after handover, so the next project starts without it.

How CCM Supports Clients With CDM 2015

CCM provides CDM consultant and Principal Designer services for commercial, retail, and EV and energy projects across Great Britain, from our base in Cheltenham. Depending on what your project needs, we can:

help you understand your client duties, review your project arrangements and identify the appointments and information required
act as Principal Designer under a written appointment, planning, managing, monitoring and coordinating health and safety in the pre-construction phase
help bring together pre-construction information, identify gaps and coordinate designers on foreseeable design risks
as Principal Designer, prepare, review and update the health and safety file
liaise with the Principal Contractor about design risks that need managing during construction

Where we also provide Construction Project Management, CDM coordination can be aligned with the programme, procurement and reporting on your project.

Appointing CCM does not take your client duties away from you. The written appointment sets out exactly what we have accepted, and the client and every other duty holder remain responsible for their own duties under CDM 2015. To discuss a project, see our CDM Services or contact us.

Frequently Asked Questions

Do I need to comply with the CDM Regulations?

Yes, if you are having construction work carried out in Great Britain. CDM 2015 applies to every construction project, regardless of size or value. Commercial clients carry the client duties themselves. On domestic projects, those duties pass to the contractor, the Principal Contractor or, by written agreement, the Principal Designer.

What are the five main parts of CDM 2015?

CDM 2015 is split into five parts. Part 1 covers definitions and where the regulations apply. Part 2 sets out the client’s duties, including appointments and notification. Part 3 covers the health and safety duties and roles of designers, contractors, the Principal Designer and the Principal Contractor. Part 4 sets general requirements for all construction sites, such as site security, excavations, traffic routes and fire. Part 5 covers general matters, including transitional provisions.

How do I comply with CDM 2015 as a client?

Start early. Make suitable arrangements for the project and allow enough time and resources, appoint competent designers and contractors, and appoint a Principal Designer and Principal Contractor in writing if more than one contractor will be involved. Provide pre-construction information, make sure a construction phase plan is in place before work starts, notify HSE if the project is notifiable, and keep the health and safety file where one is required.

Is a CDM consultant the same as a Principal Designer?

No. “CDM consultant” is not a role defined in CDM 2015; it describes someone who advises a client or project team on CDM. The Principal Designer is a formal duty holder: a designer with control over the pre-construction phase, appointed in writing. Some firms, including CCM, offer both, but they are different appointments.

Who keeps the health and safety file after the project?

The client. At the end of the project, the Principal Designer, or the Principal Contractor if the Principal Designer’s appointment has already ended, hands the file to the client. The client must keep it available for anyone who needs it for future work on the building, and pass it to the new owner if they sell their interest.