CDM Regulations 2015 Explained Simply

The Construction (Design and Management) Regulations 2015 are the main set of regulations for managing health and safety on construction projects in Great Britain. They replaced CDM 2007 and apply to every construction project, regardless of size. Despite being in force for over a decade, many people in the industry still find them confusing. This guide explains CDM 2015 in plain English, without the legal jargon.

What Is CDM 2015?

CDM stands for Construction (Design and Management). The 2015 regulations came into force on 6 April 2015 and replaced the earlier 2007 version. The core purpose is straightforward: to make sure health and safety is properly considered throughout the entire life of a construction project, from the initial design concept through to completion and handover.

The regulations are enforced by the Health and Safety Executive (HSE). Non-compliance can result in enforcement notices, prosecution, and significant fines. In the event of a fatality, directors and individuals can face criminal charges including corporate manslaughter.

One of the most important changes in 2015 was removing the threshold that previously exempted smaller projects. Under CDM 2007, many requirements only applied to notifiable projects. Under CDM 2015, all construction work is covered, whether it is a multi-million pound development or a single tradesperson fitting a kitchen.

Who Does It Apply To?

CDM 2015 applies to everyone involved in a construction project:

• Clients who commission the work
• Designers who prepare or modify designs
• Contractors who carry out the construction work
• Workers on site

The term "construction work" is broadly defined. It includes building, alteration, fitting out, commissioning, renovation, repair, upkeep, redecoration, maintenance, decommissioning, demolition, dismantling, and any associated site clearance, exploration, or temporary works. In practice, almost anything that involves physical work on a building or structure falls within CDM.

The regulations apply in England, Scotland, and Wales. Northern Ireland has its own separate CDM regulations (CDM NI 2016) which are broadly similar.

The Five Duty Holders Explained

CDM 2015 identifies five categories of duty holder, each with specific legal obligations.

1. Clients

The client is the person or organisation for whom the construction work is being carried out. Their duties include:

• Making suitable arrangements for managing the project, including allocating sufficient time and resources
• Appointing a principal designer and principal contractor (on projects with more than one contractor)
• Providing pre-construction information to designers and contractors
• Ensuring a construction phase plan is prepared before construction begins
• Ensuring welfare facilities are in place before work starts

Clients do not need to manage health and safety themselves, but they must make sure someone competent is doing it.

2. Domestic Clients

A domestic client is someone who has construction work done on their own home or the home of a family member, where the work is not in connection with a business. Domestic clients have the same duties as commercial clients, but those duties are automatically transferred to the contractor (on single-contractor projects) or the principal contractor (on multi-contractor projects).

In practice, this means the domestic client does not need to do anything specific under CDM, but the contractor picks up the responsibility.

3. Principal Designers

The principal designer is the designer appointed by the client to plan, manage, monitor, and coordinate health and safety in the pre-construction phase. This is not the same as the lead designer or architect. The principal designer role is specifically about health and safety in design.

Their duties include:

• Planning, managing, and monitoring the pre-construction phase
• Coordinating matters relating to health and safety during pre-construction
• Identifying, eliminating, or controlling foreseeable risks through design
• Preparing the health and safety file
• Providing pre-construction information to the principal contractor

4. Principal Contractors

The principal contractor is appointed by the client on projects with more than one contractor. They are responsible for the construction phase. Their duties include:

• Planning, managing, and monitoring the construction phase
• Preparing the construction phase plan
• Organising cooperation between contractors
• Ensuring site inductions are carried out
• Ensuring welfare facilities are maintained
• Consulting and engaging with workers on health and safety
• Liaising with the principal designer

5. Designers

A designer is anyone who prepares or modifies designs for a building, product, or system relating to construction work. This includes architects, engineers, surveyors, and anyone who specifies materials or methods. Designers must:

• Consider the health and safety implications of their designs
• Eliminate foreseeable risks where possible
• Reduce risks that cannot be eliminated
• Provide information about remaining risks

When Do You Need to Notify the HSE?

Not all projects need to be notified to the HSE. Notification is required when a project:

• Will last longer than 30 working days AND will have more than 20 workers on site at any one time, OR
• Will exceed 500 person-days of construction work

Notification must be done by the client (or someone acting on their behalf) before the construction phase begins. It is submitted to the HSE online through the F10 notification form. The notification must be displayed in the site office where workers can see it.

Even if a project does not meet the notification threshold, CDM 2015 still applies in full. The only thing that changes is the requirement to notify.

Key Documents Required Under CDM

CDM 2015 requires several key documents to be produced and maintained:

Pre-Construction Information

Provided by the client to the principal designer and principal contractor. This includes information about the existing site, previous use, any known hazards (such as asbestos), ground conditions, and any client requirements or restrictions.

Construction Phase Plan

Prepared by the principal contractor before work starts. This sets out how health and safety will be managed during the construction phase. See our construction phase plan template for a detailed breakdown of what to include.

Health and Safety File

Prepared by the principal designer and handed to the client at completion. This contains information needed for future maintenance, repair, renovation, or demolition of the building. It is a record for the life of the structure, not just the construction phase.

Common Questions About CDM 2015

Does CDM apply to maintenance work?

Yes. The definition of construction work includes maintenance, repair, and upkeep. Even a single tradesperson carrying out repair work on a building is covered by CDM 2015.

What about work on domestic properties?

CDM applies to domestic projects. The difference is that the domestic client's duties transfer automatically to the contractor or principal contractor. The contractor still needs to plan the work properly and manage health and safety.

Can one person hold multiple CDM roles?

Yes, within limits. A designer can also be the principal designer. A contractor can also be the principal contractor. On single-contractor domestic projects, the contractor takes on both the principal contractor and principal designer roles by default.

What happens if you do not comply?

The HSE can issue improvement notices, prohibition notices (stopping work immediately), or prosecute. Fines for CDM breaches can be substantial. In 2025, several construction companies received fines exceeding one million pounds for CDM failures that led to serious injuries or fatalities.

Practical Steps for Compliance

CDM compliance does not need to be complicated. Here is what you should focus on:

1. Understand your role - know which duty holder category you fall into and read the specific duties for that role in the regulations
2. Appoint competently - make sure the people you appoint as principal designer, principal contractor, and individual contractors have the skills, knowledge, experience, and organisational capability for the project
3. Provide information early - the earlier designers and contractors receive pre-construction information, the better they can plan to manage risks
4. Plan before you start - the construction phase plan must exist before anyone sets foot on site. Do not start work without it.
5. Communicate - site inductions, toolbox talks, and regular briefings ensure everyone understands the risks and the plan
6. Monitor and review - check that the arrangements described in the phase plan are actually being implemented. Walk the site. Talk to workers. Audit compliance.
7. Keep records - document your decisions, inspections, briefings, and any changes to the plan. If the HSE visits, records demonstrate compliance.

Final Thoughts

CDM 2015 is not about generating paperwork. It is about making sure that health and safety is genuinely considered and managed throughout a construction project. The regulations place duties on specific people to ensure that no one falls through the gaps. If you understand your role, plan your work, and communicate effectively, compliance follows naturally.

The key message of CDM 2015 is simple: plan the work, manage the risks, and keep people safe. Everything else is detail.