Compliance Guide

CDM 2015 Explained: The Regulations, Duty Holders and Duties for UK Site Managers

A plain English pillar guide to the Construction (Design and Management) Regulations 2015.

CDM 2015 is the legal backbone of health and safety management on UK construction projects. It sets out who is responsible for what, from the client who commissions the work down to the workers on site. This guide explains what the regulations cover, who the duty holders are, when a project has to be notified to the HSE, and the documents you are expected to produce, written for real site managers and principal contractors rather than lawyers.

What CDM 2015 is

CDM 2015 stands for the Construction (Design and Management) Regulations 2015. It is the main set of health and safety regulations for construction work in Great Britain, made under the Health and Safety at Work etc. Act 1974 and enforced by the Health and Safety Executive (HSE). It came into force on 6 April 2015, replacing the earlier CDM 2007 regulations, and it is supported by the HSE guidance document L153.

The core idea is simple: health and safety should be planned, managed and coordinated across the whole life of a project, not left to chance on site. CDM 2015 does that by placing specific legal duties on the people who are best placed to manage risk at each stage, from design through to construction and beyond.

When CDM 2015 applies

This is the point most people get wrong, so it is worth being clear. CDM 2015 applies to all construction work, of every size, commercial and domestic. There is no lower threshold below which the regulations stop applying. A single joiner refitting a kitchen is doing construction work covered by CDM, just as a multi million pound commercial development is.

What changes with the size and nature of the project is not whether CDM applies, but how much of it applies and to whom. Two things in particular scale up:

Whether more than one contractor is involved, which triggers the appointment of a principal designer and a principal contractor.
Whether the project is notifiable to the HSE, which triggers the F10 notification.

For domestic clients (someone having work done on their own home, not connected to a business), the client duties normally pass to the contractor on a single contractor job, or to the principal contractor on a project with more than one contractor. The client does not escape the duties, they simply sit with someone else.

The five CDM 2015 duty holders

CDM 2015 defines five duty holders. Knowing which one you are, and which one everyone else on the project is, is the single most useful thing to take from these regulations. Workers also have duties, which is why they are covered below as well.

1. The Client

The client is the organisation or individual for whom the construction project is carried out. The client sits at the top of the chain and sets the tone. Their duties include making suitable arrangements for managing the project, providing pre-construction information to designers and contractors, ensuring the right duty holders are appointed, ensuring welfare facilities are provided, and confirming a construction phase plan is in place before work starts. The client cannot simply hand the whole thing over and walk away; the duty to make sure the arrangements are working stays with them.

2. The Principal Designer

The principal designer is appointed by the client on any project involving more than one contractor. This is a designer with control over the pre-construction phase, not a job title for a specific person. Their role is to plan, manage, monitor and coordinate health and safety during design and planning. That means eliminating foreseeable risks through design where possible, reducing what cannot be eliminated, and passing information on the risks that remain to the principal contractor. The principal designer also prepares and updates the health and safety file.

3. The Principal Contractor

The principal contractor is appointed by the client on any project with more than one contractor, and is usually the organisation actually running the site. If you are a site manager, this is very often the duty holder you are working for. The principal contractor plans, manages, monitors and coordinates health and safety during the construction phase. Their duties include drawing up the construction phase plan, organising cooperation between contractors, controlling site access, providing site induction and welfare, and consulting workers on health and safety.

4. Designers

A designer is anyone who prepares or modifies a design, or arranges for or instructs someone else to. That includes architects, engineers, and in practice trades who make design decisions. Designers must eliminate, reduce or control foreseeable risks that may arise during construction and in the future use of the building, and provide information about remaining risks to those who need it.

5. Contractors

A contractor is anyone who carries out, manages or controls construction work. That covers most companies and trades on site. Contractors must plan, manage and monitor their own work so it is carried out without risks to health and safety, comply with directions from the principal contractor, and not start work until they have taken reasonable steps to prevent access by unauthorised people. On a single contractor project, that one contractor also picks up duties that would otherwise fall to the principal contractor.

And workers

Workers are the people who carry out the work. Under CDM they must be consulted on matters affecting their health and safety, must be given a suitable site induction and the information and training they need, must cooperate with the employer or other duty holders, and must report anything they see that is likely to endanger themselves or others. They also have to look after their own safety and that of others affected by their work.

The quick test: on any project, ask two questions. Is there more than one contractor? If yes, a principal designer and principal contractor must be appointed in writing. Is the project notifiable? If yes, an F10 must be sent to the HSE. Get those two answers right and the rest of the CDM structure falls into place.

When is a project notifiable to the HSE?

Some projects must be notified to the HSE using form F10. A project is notifiable if the construction work is scheduled to either:

last longer than 30 working days and have more than 20 workers working simultaneously at any point on the project, or
exceed 500 person days of construction work.

These are the two real thresholds. Meeting either one makes a project notifiable. Person days is simply the number of workers multiplied by the number of days they work, so a job with 10 workers over 60 days is 600 person days and is notifiable on that basis alone. The F10 is the client's duty to submit, though in practice it is often prepared by the principal contractor or principal designer on the client's behalf.

A common misconception worth correcting: notification does not decide whether CDM applies. CDM applies to every project regardless of the F10. Notification is an additional step for larger projects, not a switch that turns the regulations on.

The key CDM 2015 documents

CDM 2015 revolves around a small number of documents. Knowing which is required when, and who owns it, keeps you out of trouble during an HSE visit.

Pre-construction information

Pre-construction information is the health and safety information the client already holds or can reasonably obtain about the site and the project: existing services, asbestos surveys, ground conditions, structural information, site constraints and so on. The client must provide it to every designer and contractor who is, or may be, appointed. It feeds the design decisions and, in turn, the construction phase plan.

The construction phase plan

The construction phase plan is required on every single construction project, no matter how small, and it must be in place before construction work starts. It sets out the health and safety arrangements, site rules and specific measures for the work being carried out. On a single contractor job the contractor draws it up; on a project with more than one contractor the principal contractor does. It should be proportionate, a short focused plan for a small job and a fuller one for a complex project, and it is a live document that is updated as the work changes.

The health and safety file

The health and safety file is only required for projects involving more than one contractor. It contains the information anyone carrying out future construction, maintenance, cleaning or demolition will need to do that work safely: as built drawings, details of remaining hazards such as asbestos left in place, structural information, and the specification of key equipment. The principal designer prepares and updates it, and hands it to the client at the end of the project. The client must keep it and make it available to anyone who needs it in future.

Document	When required	Who owns it
Pre-construction information	Every project	Client provides to designers and contractors
Construction phase plan	Every project, before work starts	Principal contractor, or the contractor on a single contractor job
Health and safety file	Projects with more than one contractor	Principal designer prepares, client keeps
F10 notification	Notifiable projects only	Client submits to the HSE

What a site manager actually has to do

If you run a site for a principal contractor, CDM 2015 turns into a fairly practical daily checklist. The regulations sit behind almost everything you already do.

Confirm the appointments are in writing. On a multi contractor job, check that a principal designer and principal contractor have been appointed in writing before work starts. If they have not, the client duties default back to the client, and that is a gap.
Have the construction phase plan ready before work begins. Not after the first pour. It has to exist and be relevant to the actual job, and you should be able to produce it on request.
Check whether the project is notifiable. Run the 500 person day or the 30 days plus 20 workers test. If it is notifiable, confirm the F10 has been submitted and displayed on site.
Induct everyone and control access. Site induction, welfare facilities and controlled access are principal contractor duties that land on the site manager in practice.
Coordinate the contractors. Make sure trades are not creating risks for each other, that RAMS are reviewed before work starts, and that cooperation is actually happening, not just assumed.
Feed the health and safety file. Capture as built changes, retained hazards and key information as you go, so the file the client receives is accurate rather than reconstructed at the end.

The risk assessments and method statements each trade produces are how they demonstrate that planning under CDM. If you want the detail on producing those, see our step by step guide on how to write a RAMS for a UK construction project.

Common CDM 2015 failings

Assuming small jobs are exempt. They are not. CDM applies to all construction work, including domestic.
Starting work with no construction phase plan. Required on every project before work starts, with no exceptions for size.
No written appointment of the principal designer or principal contractor. On a multi contractor project this is a legal requirement, and without it the duties do not sit where everyone assumes.
Confusing notification with application. Treating a non notifiable project as if CDM does not apply.
A construction phase plan that is a generic template. It has to reflect the actual site, hazards and sequence, the same way a RAMS does.
Forgetting the health and safety file. On multi contractor projects it must be prepared and handed to the client, then kept available for future work.

Where judgement comes in

CDM 2015 is deliberately goal setting rather than prescriptive in places. It repeatedly asks for arrangements and plans that are "suitable" and "proportionate" without defining an exact page count or format. That is a judgement call, and it should be. A loft conversion and a hospital do not need the same construction phase plan. When you are unsure how much detail is enough, the honest answer is that it depends on the risk, and the reference point is the HSE guidance L153 and the Approved Code of Practice, plus your own competent assessment of the specific job.

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Frequently asked questions

Does CDM 2015 apply to small or domestic jobs?

Yes. CDM 2015 applies to all construction work, of any size, commercial and domestic. There is no lower threshold. For a domestic client the client duties normally transfer to the contractor on a single contractor job, or the principal contractor where more than one contractor is involved, but the regulations still apply to the work itself.

When is a construction project notifiable to the HSE?

A project is notifiable, and needs an F10, if the construction work will last longer than 30 working days and have more than 20 workers working at the same time at any point, or if it will exceed 500 person days of work. Meeting either threshold makes it notifiable. Notification is the client's duty, though it is often prepared by the principal contractor or principal designer.

Who are the CDM 2015 duty holders?

There are five: the client, the principal designer, the principal contractor, designers and contractors. Workers also carry duties under CDM. The principal designer and principal contractor are only appointed when a project involves more than one contractor.

Is a construction phase plan always required?

Yes. A construction phase plan is required on every construction project, however small, and it must be in place before construction work starts. On a single contractor job the contractor prepares it; where there is more than one contractor the principal contractor does. It should be proportionate to the risk and kept up to date.

What is the difference between the construction phase plan and the health and safety file?

The construction phase plan covers how the current work will be carried out safely and is required on every project. The health and safety file is only required on projects with more than one contractor, and it holds the information needed to carry out future work on the building safely, such as retained hazards and as built details. The client keeps the file after handover.

Conclusion

CDM 2015 is less complicated than its reputation suggests once you hold onto the structure: it applies to every project, it assigns clear duties to five duty holders, it requires a construction phase plan on every job, and it adds a principal designer, a principal contractor and, where the F10 thresholds are met, an HSE notification on larger work. Get the appointments in writing, have the right documents in place before work starts, and keep them proportionate to the actual risk. Where a requirement is unclear for your specific project, check the HSE guidance L153 and your own competent assessment.

This article is general guidance for UK construction and is not legal advice. For requirements specific to your project, check current HSE guidance, including L153, and take competent advice.