CDM Regulations Guide UK — Construction Design and Management 2015 for Tradespeople (2026)

What Are the CDM Regulations 2015?

The Construction Design and Management Regulations 2015 (CDM 2015) are the main piece of health and safety law covering the construction industry in Great Britain. They replaced the earlier CDM 2007 regulations and are enforced by the Health and Safety Executive (HSE).

CDM 2015 applies to all construction work — not just large new-build developments. Maintenance, refurbishment, repair, decoration, and even minor alteration work all fall within scope. If you're carrying out any kind of building work on behalf of a client, CDM duties apply to you.

The regulations exist to improve health, safety, and welfare across all construction projects by making sure the right people plan and manage risk throughout the project lifecycle — from initial design right through to handover and beyond.

When Do CDM Regulations Apply?

CDM 2015 applies to every construction project, regardless of size. Every project has at least some CDM duties — but the level of obligation scales with the project.

The key threshold is HSE notification. A project must be notified to the HSE (using the F10 online form) if it meets either of the following criteria:

• The construction phase will last more than 30 working days and will have more than 20 workers simultaneously on site at any point, or
• The project will exceed 500 person-days of construction work in total.

Once either threshold is crossed, the project is notifiable and must have a Principal Designer (PD) and Principal Contractor (PC) formally appointed. Below the thresholds, you still have CDM duties — there's just no formal notification obligation and no requirement for a PD on the smallest jobs.

The Five CDM Dutyholder Roles

CDM 2015 defines five dutyholder roles. Understanding which role applies to you on any given project is the starting point for knowing what you must do.

• Client — the organisation or individual for whom the construction work is carried out. Can be a commercial client or a domestic homeowner. Commercial clients have more duties than domestic clients.
• Principal Designer (PD) — appointed by the client on projects with more than one contractor. Usually an architect or design practice, but can be any designer with the right skills. Leads health and safety during the pre-construction phase.
• Designer — anyone who prepares or modifies designs for construction work, including drawings, specifications, and bills of quantities. Architects, structural engineers, surveyors, and even contractors who design temporary works are all designers.
• Principal Contractor (PC) — appointed by the client on projects with more than one contractor. Takes overall responsibility for managing health and safety during the construction phase.
• Worker — anyone who works on site carrying out construction work. Every worker has duties under CDM 2015, not just management.

On smaller projects with a single contractor, the roles overlap. For domestic projects, the contractor can take on the client's CDM duties if no formal appointment is made. Where there is only one contractor on a project, that contractor takes on the PC duties automatically.

Client Duties Under CDM 2015

Commercial clients carry the heaviest CDM obligations. If you're managing work for a commercial client — a landlord, property developer, facilities manager, or business — those client duties are theirs to fulfil, but you need to understand what to expect from them.

• Appoint a suitable Principal Designer in writing before the pre-construction phase begins.
• Appoint a suitable Principal Contractor in writing before the construction phase begins.
• Provide pre-construction information to the PD and PC — utility drawings, asbestos surveys, structural surveys, existing health and safety files, ground investigation reports.
• Ensure suitable management arrangements and sufficient time and resources are allocated throughout the project.
• Maintain and pass on the health and safety file once the project is complete.

Domestic clients (homeowners commissioning work on their own home) have reduced duties. If they don't appoint a PD, the designer in control of pre-construction takes on that role. If they don't appoint a PC, the contractor in control of the construction phase takes on the PC duties.

Principal Designer Duties

The Principal Designer (PD) leads health and safety during the pre-construction phase — before a single piece of ground is broken. This is often an architect or lead design consultant, but must be someone with the skills, knowledge, and experience to do the job properly.

• Plan, manage, monitor, and coordinate health and safety throughout pre-construction.
• Identify and eliminate foreseeable risks during the design stage — not just document them.
• Gather pre-construction information from the client and pass it to designers and contractors.
• Ensure all designers cooperate and coordinate their work to reduce risk.
• Produce and maintain the health and safety file during the pre-construction phase, then hand it to the PC to update during construction.
• Liaise with the PC throughout the project to share information.

The PD role ends when the construction phase begins, but responsibility for the health and safety file stays with the PD until the PC takes it over — and returns to the client at handover.

Principal Contractor Duties

The Principal Contractor (PC) is the main contractor on site — responsible for planning, managing, and monitoring health and safety throughout the construction phase. If you're the lead contractor managing other trades on a project, this is almost certainly your role.

• Produce a Construction Phase Plan (CPP) before work starts on site — this is a legal requirement.
• Set up and maintain suitable welfare facilities before the construction phase begins.
• Organise site inductions for all workers before they start work.
• Manage and coordinate the activities of all contractors and subcontractors on site.
• Prevent unauthorised access to the site.
• Consult with workers and ensure they have the right information, instruction, and training.
• Update and maintain the health and safety file during the construction phase.

If you're the only contractor on a project, you take on PC duties automatically — even on a small domestic job. The scale of your CPP can be proportionate to the project, but it must exist and be in place before work starts.

Worker Duties Under CDM 2015

CDM 2015 places duties on workers — not just management. Every person carrying out construction work on site has legal obligations.

• Take reasonable care of your own health and safety and that of others who may be affected by your work.
• Follow site rules and comply with instructions given by the PC or supervisor.
• Report any unsafe situation or shortcoming in health and safety arrangements without delay.
• You have the right to stop work and leave the area if you believe there is a risk of serious and imminent danger — and you cannot be penalised for doing so.
• Cooperate with employers and other dutyholders on health and safety matters.

Workers must also be consulted on matters that affect their health and safety. The PC has a duty to consult — but workers also have a responsibility to engage.

Pre-Construction Information

Pre-construction information is the package of existing information about the site and structure that the client must gather and share before tendering or appointing contractors. It's one of the most practically important CDM requirements for trade contractors.

If this information is incomplete or missing, you should flag it before starting work — not after. As the PC or lead contractor, you have a duty to request it. Proceeding without it — particularly asbestos information on pre-2000 buildings — is a serious breach of CDM and carries significant HSE enforcement risk.

If the client cannot provide the information, a survey should be commissioned before work starts, not during it.

The Construction Phase Plan

The Construction Phase Plan (CPP) is the document that sets out how health and safety will be managed on site during the construction phase. It's a legal requirement — and it must be ready before work begins on site.

The PC is responsible for writing and maintaining the CPP. It should be proportionate to the project — a simple refurbishment needs a much shorter plan than a major new build — but it must contain certain minimum elements:

• Project description — nature of the work, programme, key milestones
• Contact details — client, PD, PC, emergency contacts
• Site-specific risks — identified hazards and control measures
• Welfare arrangements — toilets, hand-washing, rest facilities, drinking water
• Emergency procedures — evacuation routes, assembly points, first aid provision
• First aid — first aider details, first aid kit location
• Site rules — PPE requirements, permit to work processes, restricted areas
• Subcontractor management — how other contractors will be coordinated

The CPP is a live document — it should be updated as the project progresses and conditions change. Keep a copy on site at all times.

The Health and Safety File

The health and safety file is a record of information that future owners, occupiers, or contractors will need to carry out work on the building safely. It's created during the project and handed to the client at completion.

The PD is responsible for creating and maintaining the file during the pre-construction phase. The PC takes it over during construction, adds to it, and hands it to the client at handover. For notifiable projects, producing the file is mandatory.

Typical contents include:

• As-built drawings and structural information
• Operation and maintenance manuals for installed plant and equipment
• Materials specifications — particularly for hazardous materials that remain in the structure
• Details of services routes (electrical, gas, water, drainage)
• Information about any residual risks that cannot be eliminated — e.g. asbestos left in situ
• Emergency procedures relevant to the completed building

The file stays with the building — not the contractor. If the building is sold, it transfers to the new owner. When future work is carried out, the file becomes the pre-construction information for the next project. Keeping it complete and accurate matters beyond the immediate job.