CDM Regulations 2015
Construction (Design and Management) Regulations 2015 (SI 2015/51), supported by HSE L153 Managing health and safety in construction
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Why This Matters for Part 3
CDM 2015 is one of the most heavily tested regulations in Part 3. Examiners probe the five duty holder roles and their precise statutory duties, the client's overarching responsibility, the notification thresholds under Regulation 6, the difference between the Pre-construction Information and the Construction Phase Plan, and the relationship between the CDM Principal Designer and the new statutory Principal Designer under the Building Safety Act 2022. Candidates are expected to quote regulation numbers, not just describe duties in general terms.
The Construction (Design and Management) Regulations 2015 (SI 2015/51) are the primary statutory instrument governing health and safety in UK construction. They came into force on 6 April 2015, replacing CDM 2007, and abolished the CDM Coordinator role in favour of a new Principal Designer role to be held by a member of the design team. The regulations apply to every construction project, however small, and place specific duties on five categories of duty holder: clients, designers, principal designers, principal contractors, and contractors. The 2015 regulations were the first to bring domestic clients into scope, although their duties are transferred to others by default. HSE guidance L153 is the official companion document.
Duty Holder Framework
Client Duties
CDM 2015 Regulation 4
The client carries the primary responsibility for setting standards and making suitable arrangements for managing health and safety on the project. Regulation 4 requires the client to ensure that suitable arrangements are in place, that sufficient time and resources are allocated, that the Principal Designer and Principal Contractor are appointed when more than one contractor is involved, and that the Pre-construction Information is provided. The client must check duty holder competence before appointment.
Examiners often ask who is 'ultimately responsible' for site safety. The answer is the client under Regulation 4, even when work is delegated. The architect should never let a client believe they can transfer this duty away.
Designer Duties
CDM 2015 Regulation 9
Every designer (including the architect) must, when preparing or modifying a design, eliminate foreseeable risks to anyone affected by the construction, use, maintenance, or demolition of the building. Where risks cannot be eliminated, the designer must reduce or control them through the design and provide information about the residual risks. Designer duties apply from the earliest concept stage, not only from technical design.
The duty under Reg 9 is to eliminate so far as is reasonably practicable, then reduce, then inform. This hierarchy is examined directly. Saying you would only 'provide information' without first trying to eliminate the risk is a wrong answer.
Principal Designer Duties
CDM 2015 Regulation 11 and Regulation 12
The Principal Designer (PD) is appointed by the client where more than one contractor is involved. Regulation 11 requires the PD to plan, manage, monitor, and coordinate health and safety during the pre-construction phase. The PD must assist the client in preparing the Pre-construction Information, ensure designers cooperate, and prepare the Health and Safety File. Regulation 5 requires the appointment to be in writing.
Do not confuse the CDM PD with the BSA 2022 PD. The CDM PD is appointed under Reg 5 of CDM 2015. The BSA PD is appointed under s.31 of the Building Safety Act 2022 and applies only to higher-risk buildings. The same person may hold both roles if competent for each.
Principal Contractor Duties
CDM 2015 Regulation 12 and Regulation 13
The Principal Contractor (PC) is appointed by the client where more than one contractor is involved. Regulation 12 requires the PC to plan, manage, monitor, and coordinate health and safety during the construction phase. The PC prepares the Construction Phase Plan before construction begins, ensures site rules are in place, controls site access, and coordinates contractors. Regulation 13 details specific duties including induction and consultation with workers.
Contractor Duties
CDM 2015 Regulation 15
Every contractor must plan, manage, and monitor their own work to ensure it is carried out without risk to health and safety. Regulation 15 requires contractors to comply with directions from the Principal Contractor, provide site inductions, and ensure their workers have the necessary skills, knowledge, training, and experience. Where there is only one contractor on a project, that contractor must prepare the Construction Phase Plan themselves.
Notifiable Projects
Notification Thresholds
CDM 2015 Regulation 6
A project is notifiable to the HSE if construction work is likely to last longer than 30 working days and have more than 20 workers working simultaneously at any point, OR if it will exceed 500 person-days. Either limb triggers notification. The two limbs are alternatives, not cumulative. Domestic projects under Regulation 7 are not exempt from notification if the thresholds are met.
The thresholds are AND within the first limb (30 days AND 20 workers simultaneously), but OR between the two limbs (30+20 OR 500 person-days). Examiners test this with carefully framed numbers, so read the question precisely.
F10 Form to HSE
CDM 2015 Regulation 6(2) and Schedule 1
Notification is made via the F10 form, submitted electronically to the HSE before construction begins. Schedule 1 lists the required information: client details, project address, anticipated dates, duty holder names, and brief project description. The client must ensure the notice is displayed on site in a position visible to workers. Failure to notify a notifiable project is a criminal offence.
Domestic Client Rule
CDM 2015 Regulation 7
A domestic client (one having work done not in connection with a business) cannot themselves be expected to discharge client duties. By default, the client duties pass to the contractor on a single-contractor project, or to the Principal Contractor on a multi-contractor project, unless there is a written agreement transferring the duties to the Principal Designer. The architect should make this transfer explicit at appointment.
If asked who carries client duties on a domestic project: default is contractor or Principal Contractor. The PD can take them on by written agreement. The domestic client never escapes scope of CDM, the duties simply transfer.
Pre-construction Information and Construction Phase Plan
Pre-construction Information (PCI)
CDM 2015 Regulation 4(4) and Appendix 2 of HSE L153
The client must provide Pre-construction Information to every designer and contractor on the project as soon as practicable. The PCI must include information already in the client's possession, or reasonably obtainable, that is relevant to the project. Typical contents: existing surveys, asbestos register, ground conditions, services drawings, structural information, site constraints, and any client requirements. The Principal Designer assists the client with the PCI.
Construction Phase Plan (CPP)
CDM 2015 Regulation 12(1) and Appendix 3 of HSE L153
The Principal Contractor must prepare the Construction Phase Plan before construction begins. The CPP sets out the health and safety arrangements, site rules, and specific measures for high-risk work. It must be proportionate to the scale and risk of the project. On a single-contractor project, the sole contractor prepares the CPP. The plan must be kept under review and updated as the project progresses.
Construction must not start until the CPP is in place. The PD should advise the client that letting work begin before the CPP exists is a breach of Reg 12. Watch for scenarios where the client wants 'a quick start' and the contractor is on site without a plan.
Health and Safety File
CDM 2015 Regulation 12(5) and Appendix 4 of HSE L153
The Principal Designer prepares the Health and Safety File for projects involving more than one contractor. The File contains information for future use during occupation, maintenance, refurbishment, and demolition. On handover, the PD passes the File to the client. If the PD's appointment ends before completion, the duty transfers to the Principal Contractor under Regulation 12(8).
Coordination and Cooperation Duties
Designer Cooperation
CDM 2015 Regulation 8
Every duty holder must cooperate with any other person working on the project to the extent necessary to enable each to comply with their duties. Regulation 8 also requires designers and contractors to coordinate their work. Information sharing must be timely and in a form that the recipient can use. A designer cannot withhold information that another duty holder needs to discharge their statutory duty.
Principal Designer Coordination
CDM 2015 Regulation 11(1) to 11(7)
The PD must plan, manage, monitor, and coordinate the pre-construction phase, including the activities of all designers. The PD must ensure designers comply with their Regulation 9 duties, that information flows efficiently, and that risks identified at design stage are communicated to the Principal Contractor. The PD also liaises with the Principal Contractor through the transition into construction.
The PD's coordination duty does not make them responsible for the design itself. Each designer retains their Reg 9 duty. The PD is a coordinator, not a design checker. Examiners may test whether candidates wrongly extend the PD's liability into design adequacy.
Mutual Cooperation
CDM 2015 Regulation 14
Designers and contractors must cooperate with the client, the Principal Designer, and other duty holders. Regulation 14 reinforces Regulation 8 by making clear that no contractual silence or commercial reluctance is a defence to a failure to share safety information. The duty is statutory, not contractual, and exists regardless of the appointment terms.
Interaction with the Building Safety Act 2022
Two Principal Designer Regimes
CDM 2015 Regulation 5 and Building Safety Act 2022 s.31
Since the BSA 2022 dutyholder provisions took effect (October 2023 via the Building Regulations etc. (Amendment) (England) Regulations 2023), two separate Principal Designer roles can exist on the same higher-risk building project. The CDM PD coordinates health and safety risks during the pre-construction phase. The BSA PD coordinates compliance with Building Regulations. The two roles can be held by the same person if competent for each, but the duties are not identical.
If asked whether the CDM PD and BSA PD must be the same person: no. They can be the same, but only if the individual or organisation meets the competence requirements for both. On an HRB project, the appointment paperwork should make clear which role is being undertaken.
Competence Requirements
CDM 2015 Regulation 8(1); Building Safety (Competence and Organisational Capability) Regulations 2023
Under Regulation 8(1) of CDM 2015, no person may accept an appointment unless they have the skills, knowledge, experience, and where relevant the organisational capability to fulfil the role. On HRB projects, the Building Safety (Competence and Organisational Capability) Regulations 2023 add specific competence demonstration requirements for BSA duty holders. The CDM and BSA competence regimes operate in parallel.
Concurrent Documentation
CDM 2015 Regulation 4(4); BSA 2022 Gateway 2 submission
The PCI under CDM 2015 and the Gateway 2 information package under the Building (Higher-Risk Buildings Procedures) (England) Regulations 2023 cover related but distinct content. PCI is about safety risks for designers and contractors. Gateway 2 is about Building Regulations compliance for the Building Safety Regulator. The architect should not rely on one document to satisfy both regimes.
Dual PD appointment on mid-rise residential refurbishment crossing BSA threshold
Scenario
You are appointed as architect on a refurbishment and vertical extension of an existing seven-storey residential block in inner London. After the extension the building will be 19 metres tall with 28 residential units. The client (a registered provider) appoints you as both CDM Principal Designer (under Regulation 5) and Building Safety Act Principal Designer (under s.31 BSA 2022). The Principal Contractor is appointed at RIBA Stage 4 finalisation. Three weeks after construction starts you receive a request for information from the PC asking for asbestos survey data for a stairwell that was not previously identified as containing ACMs. The original PCI does not cover this area in detail.
Analysis
Two duties trigger simultaneously. As CDM PD under Regulation 11, you must coordinate pre-construction information and assist the client in making the PCI suitable. The gap in PCI is a Reg 4(4) issue: the client did not provide adequate information. As architect-designer you are also under Regulation 9 to eliminate or reduce risks so far as is reasonably practicable, and to inform the PC. The correct sequence is: (1) Issue written confirmation to the client that the PCI gap is a CDM 2015 Reg 4 matter and requires immediate update. (2) Instruct an intrusive asbestos refurbishment and demolition survey under the Control of Asbestos Regulations 2012 Reg 5 and 6 before any further work in that stairwell. (3) Advise the PC in writing that work in the affected area must be suspended until survey results are available. (4) Update the PCI and record the change. Under BSA 2022 s.31, you must also assess whether the survey results have any implication for the Gateway 2 information package, particularly fire compartmentation and means of escape. If they do, you may need to make a major change application to the Building Safety Regulator.
Outcome
The PC suspends work in the stairwell pending survey results. The asbestos survey identifies licensed ACMs in the stairwell lining. A licensed removal contractor is appointed. The PCI is updated, and the CPP is revised. Your contemporaneous documentation, in particular your written notice of the Reg 4 gap, protects your professional position. The client absorbs the four-week delay and additional cost. Neither the BSR notification nor a Gateway 2 change is required because the fire strategy is not affected.