The Construction (Design and Management) Regulations 2015 (CDM 2015) create five statutory duty holders with specific legal responsibilities for managing health and safety throughout the lifecycle of a construction project. Every construction project in Great Britain — regardless of size, value, or duration — involves at least one CDM duty holder, and most involve several. Understanding who these duty holders are, when they must be appointed, and what they are legally required to do is essential for anyone commissioning, designing, managing or carrying out construction work.
This guide explains the role and responsibilities of each CDM 2015 duty holder in plain English, sets out the legal requirements under the regulations, and clarifies how the system works in practice for domestic clients, commercial clients, small contractors, and multi-contractor projects.
What CDM 2015 requires from duty holders
CDM 2015 is structured around the principle that health and safety must be managed at every stage of a construction project — from initial concept through design, construction, and into future maintenance and demolition. The regulations divide these stages between five types of duty holder, each with defined legal obligations.
Under Regulation 4, clients must make suitable arrangements for managing the project and ensure other duty holders are appointed and carry out their functions. Under Regulation 5, where there is more than one contractor, the client must appoint a principal designer and a principal contractor in writing before the construction phase begins. These appointments cannot be made verbally; written confirmation is a legal requirement.
Regulation 8 places a duty on all those appointing duty holders to take reasonable steps to satisfy themselves that the appointee has the skills, knowledge, experience and organisational capability necessary to carry out the role safely. This competence assessment must be documented and must be proportionate to the complexity and risk of the project.
Regulation 15 makes clear that contractors — including sole traders and the self-employed — have duties under CDM 2015 regardless of whether they have been formally appointed as principal contractor. Every contractor must plan, manage and monitor their own work, ensure workers are competent, and cooperate with other duty holders. The HSE guidance document L153 (Managing Health and Safety in Construction) provides detailed explanation of these requirements.
Who CDM 2015 duty holders apply to
CDM 2015 applies to all construction work in Great Britain. The regulations define construction work broadly under Regulation 2(1) to include building, civil engineering, demolition, refurbishment, maintenance, decoration, installation of services, and any preparatory or ancillary work such as site clearance, scaffolding, and archaeological investigation. There is no minimum project size, value, or duration threshold — a one-day repair job carried out by a sole trader is subject to CDM 2015 in the same way as a multi-year infrastructure project.
The specific duty holders that apply to a project depend on the project structure:
- Single contractor, domestic client: The contractor takes on the client's duties automatically under Regulation 4(7). The contractor is the only duty holder and must comply with Regulation 15 contractor duties.
- Single contractor, commercial client: The client retains full Regulation 4 duties. The contractor must comply with Regulation 15. No principal designer or principal contractor is required.
- Multiple contractors, domestic client: The client must appoint a principal designer and principal contractor in writing, or the duties transfer to the contractor in control of the construction phase under Regulation 4(7).
- Multiple contractors, commercial client: The client must appoint a principal designer and principal contractor in writing before construction begins. All contractors on site remain subject to Regulation 15 duties.
Designers have duties under Regulation 9 whenever they prepare or modify a design, regardless of whether they are formally appointed. A contractor who designs a method statement or temporary works is acting as a designer and must comply with Regulation 9.
Key duties at a glance
Each CDM 2015 duty holder has distinct legal responsibilities:
- Client (Regulation 4): Make suitable arrangements for managing the project; ensure sufficient time and resources are allocated; provide pre-construction information to designers and contractors; appoint a principal designer and principal contractor where there is more than one contractor; ensure the principal designer prepares a health and safety file; retain and provide the health and safety file to anyone who needs it for future work.
- Principal designer (Regulation 11): Plan, manage, monitor and coordinate health and safety in the pre-construction phase; identify, eliminate or control foreseeable risks; ensure designers comply with their duties; prepare and provide pre-construction information; liaise with the principal contractor; prepare the health and safety file and hand it to the client at project completion.
- Principal contractor (Regulation 12): Plan, manage, monitor and coordinate the construction phase; prepare the construction phase plan and ensure it is maintained and reviewed; organise cooperation between contractors; coordinate implementation of the plan; ensure suitable site inductions; prevent unauthorised access; display the HSE F10 notification on site where required; provide information to the principal designer for the health and safety file.
- Designer (Regulation 9): Eliminate foreseeable risks in the design so far as reasonably practicable; reduce risks that cannot be eliminated; provide information about remaining risks; ensure the client is aware of their CDM duties before starting design work; take into account pre-construction information when preparing or modifying designs.
- Contractor (Regulation 15): Plan, manage and monitor own work; ensure workers have appropriate skills, knowledge and experience; provide supervision and site inductions; comply with the construction phase plan; comply with directions from the principal designer or principal contractor; report accidents, dangerous occurrences and near misses.
Penalties for non-compliance
Breaches of CDM 2015 are criminal offences under section 33 of the Health and Safety at Work etc. Act 1974. The Health and Safety Executive (HSE) enforces the regulations and has powers to issue improvement notices, prohibition notices, and to prosecute in the magistrates' court or Crown Court. In the Crown Court, fines are unlimited. Imprisonment for up to two years can be imposed for certain breaches under section 33(1)(a).
The HSE Fee for Intervention (FFI) scheme means that inspectors can charge £163 per hour (2024 rate) for time spent identifying and addressing material breaches of health and safety law. A site visit triggered by a missing construction phase plan or failure to appoint a principal designer can result in FFI invoices of several thousand pounds even where no prosecution follows.
According to HSE statistics for 2022/23, there were 45 fatal injuries to workers in the construction sector — the highest of any industry sector in Great Britain. Construction also accounted for 54 per cent of all fall from height fatalities. These figures demonstrate why CDM duty holder roles exist and why the HSE prioritises enforcement in this sector. Non-compliance with CDM 2015 is not a paperwork issue; it is a factor in preventable deaths and serious injuries.
In 2023, a principal contractor was fined £500,000 after a worker fell through a fragile roof. The HSE investigation found the principal contractor had failed to prepare a suitable construction phase plan and had not coordinated the work of contractors on site. The company pleaded guilty to breaching Regulation 13(1) of CDM 2015.
How CDM 2015 duty holders relate to risk assessments
CDM 2015 does not replace the requirement to carry out risk assessments under Regulation 3 of the Management of Health and Safety at Work Regulations 1999 (MHSWR). Every employer and self-employed person carrying out construction work must assess the risks to workers and others affected by the work, and put in place control measures to manage those risks. This duty applies regardless of whether a construction phase plan is required under CDM 2015.
For a single-contractor domestic project, the contractor must still complete a risk assessment even though no principal designer, principal contractor or construction phase plan is required. The risk assessment must be suitable and sufficient, cover the specific hazards of the work (working at height, manual handling, use of power tools, COSHH substances, excavation, electrical work), and set out the control measures that will be applied.
Where a principal contractor is appointed, the construction phase plan required under Regulation 12(1) must describe how the construction phase will be managed to ensure health and safety. The plan should reference and incorporate the risk assessments for the work being carried out. Contractors working under a principal contractor must provide their risk assessments to the principal contractor and comply with the site rules and control measures set out in the construction phase plan.
The principal designer's duties under Regulation 11 include ensuring that foreseeable risks are eliminated or controlled during the design stage. This feeds into the pre-construction information that designers and contractors use to prepare their own risk assessments. A well-executed CDM process produces better risk assessments because risks have been considered and controlled from the earliest design stage rather than being discovered on site.
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CDM 2015 duty holders and notifiable projects
Under Regulation 6, a project is notifiable to the HSE if the construction phase is expected to last longer than 30 working days and have more than 20 workers working simultaneously at any point, or if the project exceeds 500 person-days of construction work. When a project is notifiable, the client must give notice to the HSE before the construction phase begins using the F10 form available at hse.gov.uk.
The duty to notify rests with the client under Regulation 6(1). Where a domestic client's duties are transferred to the contractor or principal contractor under Regulation 4(7), the duty to notify transfers with them. The principal contractor must display a copy of the F10 notification in a prominent location on the site under Regulation 12(4).
A project does not need to be notifiable for CDM 2015 to apply. Most small domestic and commercial projects fall below the notification thresholds, but the duty holder structure, competence requirements, and contractor duties still apply. Notification is a reporting obligation, not a trigger for CDM compliance.
The principal designer role in practice
The principal designer role was introduced in CDM 2015 to replace the CDM coordinator role under the previous CDM 2007 regulations. The HSE's intention was that the principal designer should be an organisation or individual with design skills, knowledge and experience, who could integrate health and safety into the design process rather than simply coordinating others.
In practice, the principal designer is often the lead architect, structural engineer, or a specialist CDM consultancy. The client must appoint the principal designer in writing before any design work begins (Regulation 5(1)(a)). The principal designer holds the role throughout the pre-construction phase and continues to have duties during the construction phase, including liaising with the principal contractor and preparing the health and safety file.
On small projects with limited design input, determining who should be the principal designer can be unclear. The HSE guidance in L153 states that the client may appoint the principal contractor to act as principal designer if they have the necessary design skills, knowledge and experience. A groundworks contractor designing temporary works may have sufficient competence to act as principal designer on a small project involving minor structural alterations. The key test is competence under Regulation 8 — the appointee must be capable of carrying out the role.
For projects involving structural changes, extensions, new builds, or complex refurbishment, the principal designer will almost always be a design professional. The role cannot be assigned to someone who lacks the technical knowledge to identify and control design-stage risks.
The principal contractor and construction phase plan
Under Regulation 12(1), the principal contractor must draw up a construction phase plan before the construction phase begins. The plan must set out the health and safety arrangements and site rules, taking account of the pre-construction information provided by the principal designer. The construction phase plan must be maintained and reviewed throughout the project and updated as circumstances change.
The content of the construction phase plan must be proportionate to the project. For a small project involving two or three contractors working over a period of weeks, the plan may be a few pages covering welfare facilities, site induction procedures, emergency arrangements, coordination of trades, and the key risks (working at height, manual handling, COSHH, services). For a major project, the plan may be a substantial document covering traffic management, crane operations, permit-to-work systems, and detailed method statements.
The principal contractor must ensure that every contractor working on the site is provided with a copy of the relevant parts of the construction phase plan and understands the site rules. Under Regulation 12(2)(e), the principal contractor must ensure suitable inductions are provided. Under Regulation 12(2)(c), the principal contractor must take reasonable steps to prevent unauthorised access to the site.
Failure to prepare a construction phase plan before work starts is one of the most common CDM 2015 breaches identified by HSE inspectors. On single-contractor projects, no plan is required — but the moment a second contractor steps onto site, the principal contractor duties under Regulation 12 are triggered and the plan must be in place.
Contractors and subcontractors under CDM 2015
Every contractor on a construction site has duties under Regulation 15, whether they are the principal contractor, a main contractor, or a subcontractor employed for a single day. These duties are in addition to the principal contractor's duties under Regulation 12 and cannot be delegated or transferred.
Under Regulation 15(2), contractors must plan, manage and monitor their own work to ensure it is carried out without risks to health and safety. This includes conducting risk assessments for the specific tasks being carried out and ensuring that control measures are implemented. Under Regulation 15(3), contractors must ensure that every worker under their control has the necessary skills, knowledge, training and experience to carry out the work safely, or is under the supervision of someone who does.
Subcontractors must comply with directions given by the principal designer or principal contractor (Regulation 15(4)). A subcontractor cannot refuse to follow a reasonable instruction relating to health and safety, such as attending a site induction, following a permit-to-work system, or using specific access routes. If a subcontractor believes a direction is unsafe, they must raise the issue with the principal contractor rather than proceed with unsafe work.
Self-employed contractors are treated as both employers and employees for the purposes of health and safety law. A self-employed electrician working as part of a refurbishment project has the same Regulation 15 duties as a limited company contractor, including the duty to plan and manage their work, ensure their own competence, and cooperate with others on site.
For more detail on construction contractor obligations, see the CDM Regulations 2015 guide and construction risk assessment requirements.
Domestic clients and the transfer of duties
Regulation 4(7) of CDM 2015 automatically transfers a domestic client's duties to the contractor or principal contractor. A domestic client is defined in Regulation 2(1) as a client for whom a project is carried out not in the course or furtherance of a business. A homeowner commissioning a loft conversion, extension, or rewire is a domestic client. A landlord commissioning the same work on a rental property is not — they are a commercial client.
Where a domestic client engages a single contractor, that contractor takes on the client's Regulation 4 duties. Where a domestic client engages more than one contractor, the client must appoint a principal designer and principal contractor in writing under Regulation 5. If the client does not make these appointments, the duties transfer to the contractor in control of the construction phase.
This transfer mechanism is intended to protect domestic clients who lack the technical knowledge to assess competence, manage construction projects, or prepare pre-construction information. It does not exempt the project from CDM compliance — it shifts the compliance burden to the professional contractors on the job.
Domestic clients retain one key duty that does not transfer: under Regulation 4(1)(e), the client must ensure that the principal designer or principal contractor (where appointed) carries out their functions. In practice, this is rarely enforced against domestic homeowners, but the legal duty remains. A domestic client commissioning a major project may wish to appoint a project manager or contract administrator to oversee compliance on their behalf.
Designers and design risk management
Under Regulation 9, a designer is any person who prepares or modifies a design for a construction project, or arranges for another person to do so. This definition includes architects, structural engineers, building services engineers, civil engineers, quantity surveyors specifying materials, and contractors who design temporary works, formwork, scaffolding, or method statements. If you produce a drawing, specification, or written procedure that instructs how construction work is to be carried out, you are acting as a designer under CDM 2015.
Regulation 9(1)(a) requires designers to eliminate foreseeable risks to health and safety so far as reasonably practicable. Where risks cannot be eliminated, Regulation 9(1)(b) requires designers to reduce them through design changes. Under Regulation 9(1)(c), designers must provide information about remaining risks. This is a hierarchy: elimination first, then reduction, then information. Providing a warning about a residual risk without attempting to eliminate or reduce it does not comply with Regulation 9.
A structural engineer designing a residential extension can eliminate the risk of working at height during roof construction by specifying prefabricated roof trusses that can be lifted into place by crane, rather than traditional cut timber requiring prolonged work at height. That is elimination through design. If prefabrication is not feasible, the engineer can reduce risk by specifying fixed edge protection integrated into the roof structure, rather than relying on temporary barriers or personal fall protection. If residual risks remain, the engineer must provide information to contractors about safe erection sequences and load limits.
Designers must take into account pre-construction information when preparing or modifying designs (Regulation 9(2)(b)). If the principal designer has identified ground contamination, unstable ground, overhead power lines, or existing asbestos, the designer must incorporate this information into the design and ensure the design does not introduce additional risks.
Competence and organisational capability
Regulation 8 places a duty on all those appointing or engaging duty holders to take reasonable steps to satisfy themselves that the appointee has the necessary skills, knowledge, experience and organisational capability to carry out the role safely and without risk to health. This assessment must take place before the appointment is made, must be documented, and must be proportionate to the complexity and risk of the work.
For a client appointing a principal designer, reasonable steps might include: checking professional qualifications (architect, engineer, CDM consultant); reviewing evidence of previous similar projects; confirming professional indemnity insurance is in place; and requesting a brief explanation of how the principal designer role will be discharged on this project. For a straightforward domestic extension, this process may take 30 minutes. For a complex commercial project, a formal tender and competence assessment process may be appropriate.
For a principal contractor appointing a subcontractor, reasonable steps might include: checking CSCS cards or equivalent; confirming public liability insurance; reviewing method statements and risk assessments for the proposed work; checking references from previous principal contractors; and ensuring the subcontractor understands and will comply with the construction phase plan. A principal contractor who permits an uninsured, unqualified subcontractor onto site without checking competence has breached Regulation 8.
Self-employed contractors must be able to demonstrate their own competence. This may be through formal qualifications (City & Guilds, NVQ), industry cards (CSCS, ECS, CPCS), training certificates (IPAF, PASMA, asbestos awareness), or a portfolio of completed work with references. A sole trader electrician tendering for a commercial rewire should provide evidence of electrical qualifications (BS 7671 18th Edition), Part P certification, public liability insurance, and recent similar projects.
The HSE does not endorse specific competence schemes, but recognises that demonstrating compliance with Regulation 8 is easier where industry-standard schemes are used. Clients and principal contractors are entitled to set their own competence standards provided they are reasonable and proportionate to the work.
Health and safety file requirements
Under Regulation 12(5), the principal designer must prepare a health and safety file for the project. The file must contain information about the structure that will assist those carrying out future construction work, including cleaning, maintenance, alteration, refurbishment, and demolition. The file is handed to the client at the end of the project and must be revised as the structure is altered over time.
The content of the file must be proportionate and useful. For a domestic extension, the file might include as-built drawings showing the location of new drains, details of the roof construction, information about materials containing asbestos (if any), and details of structural alterations. For a large commercial building, the file might include full as-built engineering drawings, operation and maintenance manuals for building services, structural calculations, details of buried services, and records of hazardous materials.
The health and safety file is not a dumping ground for every document produced during the project. It should contain only information relevant to future construction work. CDM 2015 does not prescribe a specific format, but the HSE guidance in L153 recommends that the file should be clear, concise, easy to navigate, and stored in a format that can be updated.
Under Regulation 4(1)(f), the client must retain the health and safety file and ensure it is available to anyone who needs it for future work on the structure. A commercial client selling a property must pass the file to the new owner. A domestic client must be informed that the file exists, what it contains, and that it should be made available to contractors carrying out future work.
Cooperation and coordination requirements
CDM 2015 places specific duties on all duty holders to cooperate with others and coordinate their activities. Under Regulation 8(2), all those working on a construction project must cooperate with the client, the principal designer, and the principal contractor so far as is necessary to enable them to comply with their duties. A designer who withholds information that is relevant to construction safety, or a contractor who refuses to attend site coordination meetings, is in breach of Regulation 8(2).
Under Regulation 12(2)(b), the principal contractor must organise cooperation between contractors. This is not a passive duty — the principal contractor must actively manage coordination through site meetings, induction processes, communication systems, and ensuring that work sequences do not create risks for others. A principal contractor who allows two trades to work in the same area without coordinating their activities, resulting in a risk of falling materials or access obstruction, has failed to comply with Regulation 12(2)(b).
Under Regulation 11(4), the principal designer must liaise with the principal contractor to help plan and coordinate the construction phase. This includes sharing pre-construction information, identifying design risks that will affect construction sequencing, and ensuring the health and safety file is compiled with input from contractors on site. A principal designer who ceases involvement once planning permission is granted, and has no further contact with the principal contractor during construction, is not complying with Regulation 11(4).
