CDM 2015 Regulations: A Plain-English Summary for UK Contractors

The Construction (Design and Management) Regulations 2015 (SI 2015/51) apply to every construction project in Great Britain. Understanding the structure of the regulations — not just isolated duties — makes it easier to identify what applies to a specific project and role.

This guide works through the regulations by part, summarising what each requires and pointing to dedicated guides where more detail is needed.

CDM 2015 at a glance

The regulations replaced CDM 2007 on 6 April 2015. The major changes: the CDM coordinator role was abolished and replaced with the principal designer; domestic client duties were reduced; and the notification threshold (the F10) remained broadly similar but was clarified.

CDM 2015 is structured as four parts plus seven schedules:

Part 1 (Regulations 1-3): Interpretation and application
Part 2 (Regulations 4-7): General management duties
Part 3 (Regulations 8-14): Duty holder roles
Part 4 (Regulations 15-35): General construction site duties

The general management duties in Part 2 apply to the client, principal designer, and principal contractor. Part 3 defines what each duty holder must do. Part 4 covers on-site safety standards that apply to all contractors on all projects, regardless of size.

Part 1: Interpretation and application (Regulations 1-3)

Regulation 1 — Citation, commencement and transition provisions.

Regulation 2 — Definitions. Several key definitions:

Client: An organisation or individual for whom a construction project is carried out. Domestic clients have reduced duties; commercial clients carry the full set.
Construction work: Broadly defined. Includes building, altering, converting, fitting out, commissioning, renovating, repairing, upkeeping, redecoration, demolition, and dismantling. Also includes site preparation, excavation, and installation of mechanical, electrical, and related systems. The definition's only stated exclusion is the exploration for, or extraction of, mineral resources (and preparatory activities carried out where such exploration or extraction takes place).
Principal contractor: The contractor appointed to plan, manage, monitor, and coordinate health and safety during the construction phase.
Principal designer: The designer appointed by the client to plan, manage, monitor, and coordinate health and safety during the pre-construction phase.
Pre-construction phase: The period before the construction phase begins — design, planning, survey, investigation.

Regulation 3 — Application. CDM 2015 applies to all construction work carried out in Great Britain. There is no minimum project size.

Part 2: General management duties (Regulations 4-7)

Regulation 4 — Client duties

The client must make suitable arrangements for managing the project, allocating sufficient time and resources. Key obligations:

Appoint a principal designer (on multi-contractor projects) and a principal contractor, in writing, before the construction phase begins
Provide pre-construction information to designers and contractors
Ensure a construction phase plan is prepared before work starts
Ensure the principal designer prepares a health and safety file
Maintain oversight throughout the project

For a detailed breakdown, see our CDM client duties guide.

Regulation 5 — Appointments by the client

On a project with more than one contractor, the client must appoint:

A principal designer — a designer with control over the pre-construction phase (Regulation 5(1)(a))
A principal contractor — a contractor to coordinate the construction phase (Regulation 5(1)(b))

Both appointments must be made in writing as soon as is practicable, and in any event before the construction phase begins (Regulation 5(2)).

Both appointees must have the skills, knowledge, experience, and organisational capability needed for the role. If the client fails to make either appointment, the client assumes the relevant duties.

Regulation 6 — Notification (the F10)

A project is notifiable if construction work on the site is expected to:

(a) last more than 30 working days AND have more than 20 workers simultaneously at any point, OR

(b) exceed 500 person-days of construction work

On notifiable projects, the client must send written notice to HSE before the construction phase begins. The notice must contain the particulars listed in Schedule 1 and include a client declaration. See our guide to CDM F10 notifications.

Regulation 7 — Application to domestic clients

Domestic clients (those having work done on their own home for non-business purposes) have reduced duties. Except on notifiable projects, domestic client duties transfer under Regulation 7(1) as follows: on a single-contractor project, duties transfer to the contractor; on a multi-contractor project, duties transfer to the principal contractor; where a principal designer is appointed and there is a written agreement, duties transfer to the principal designer instead. This means the contractor or principal contractor takes on the client's CDM management duties — which is relevant for house-builders, extension contractors, and domestic refurbishment contractors.

Part 3: Duty holder roles (Regulations 8-14)

Regulation 8 — General duties of persons at work

Every person who is an employer, self-employed person, or employee working on a project must:

Plan, manage, and monitor construction work under their control to ensure risks are managed so far as is reasonably practicable
Satisfy themselves that any contractor they appoint has the skills, knowledge, experience, and organisational capability for the work
Provide workers with appropriate supervision and information

For principal contractors, this is the basis for the competence checks carried out on subcontractors before appointment. See our subcontractor compliance checklist.

Regulation 9 — Duties of designers

Every designer must:

Not commence work unless satisfied the client is aware of the client's CDM duties (Regulation 9(1))
When preparing or modifying designs, consider the prevention principles and available pre-construction information to eliminate foreseeable health and safety risks (Regulation 9(2))
Where risks cannot be eliminated, reduce or control them, and provide risk information to the principal designer and the health and safety file (Regulation 9(3))
Provide sufficient information with the design to assist the client, other designers, and contractors (Regulation 9(4))

Regulation 10 — Designs prepared outside Great Britain

Where a designer prepares or modifies a design outside Great Britain for use in a construction project in Great Britain, the regulation adjusts certain requirements to reflect the international dimension. The core design duties of Regulation 9 still apply.

Regulation 11 — Principal designer duties

The principal designer must plan, manage, monitor, and coordinate health and safety during the pre-construction phase. Specific duties:

Apply the prevention principles when design and organisational decisions are being made
Identify and eliminate or control foreseeable risks (Regulation 11(3))
Ensure all designers comply with their Regulation 9 duties (Regulation 11(4))
Ensure cooperation across the project team (Regulation 11(5))
Assist the client with pre-construction information and ensure it reaches everyone who needs it (Regulation 11(6))
Liaise with the principal contractor throughout (Regulation 11(7))

See our guide to principal designer duties.

Regulation 12 — Construction phase plan and health and safety file

The principal contractor must prepare a construction phase plan before the construction phase begins (Regulation 12(1)). The plan must address the matters in Schedule 3 (high-risk work categories) and must be updated as the project progresses.

The principal designer must prepare a health and safety file for each project. The file records residual risks and health and safety information for the structure's future owners and anyone carrying out future maintenance or construction work. At project completion, the file is handed to the client.

For the construction phase plan, see our practical guide to construction phase plans. For the health and safety file, see our CDM health and safety file guide.

Regulation 13 — Principal contractor duties

The principal contractor plans, manages, monitors, and coordinates health and safety during the construction phase. Key specific duties:

Organise cooperation between contractors and coordinate their activities
Ensure all contractors have the information they need for safe working
Ensure inductions are provided
Consult and engage with workers about health and safety
Prevent unauthorised access to the construction site

For the full duty list, see our CDM principal contractor duties guide.

Regulation 14 — Principal contractor's duty to consult and engage workers

Workers must be consulted about matters that could affect their health and safety, and given the opportunity to participate in the arrangements for managing risk. This is a specific legal duty alongside the general consultation requirements under the Safety Representatives and Safety Committees Regulations 1977 and the Health and Safety (Consultation with Employees) Regulations 1996.

Regulation 15 — Duties of contractors

All contractors on a project — not just the principal contractor — must:

Plan, manage, and monitor their own work to ensure it is carried out without risks
Comply with directions from the principal contractor
Report anything inconsistent with the construction phase plan to the principal contractor
Provide workers with information on site risks and emergency procedures

Part 4: General construction site duties (Regulations 16-35)

Part 4 covers the physical safety standards that apply on all construction sites. These apply to all contractors on all projects, not just the principal contractor. They cover:

Safe places of work (Regulation 16)
Stability of structures (Regulation 17)
Demolition and dismantling (Regulation 18)
Explosives (Regulation 19)
Excavations (Regulation 20)
Cofferdams and caissons (Regulation 21)
Reports of inspections of excavations, cofferdams, and caissons (Regulation 22)
Energy distribution installations (Regulation 23)
Prevention of drowning (Regulation 24)
Traffic routes (Regulation 25)
Vehicles (Regulation 26)
Prevention of risk from fire (Regulation 27)
Emergency procedures (Regulation 28)
Emergency routes and exits (Regulation 29)
Fire detection and fire-fighting (Regulation 30)
Fresh air (Regulation 31)
Temperature and weather protection (Regulation 32)
Lighting (Regulation 33)
Welfare facilities (Regulation 34)
Schedules (Regulation 35)

These are largely carried forward from earlier construction site regulations, with some updates to align with the revised duty holder structure.

Schedules

Seven schedules support the regulations:

Schedule 1 — Prescribed particulars for the F10 notification (15 items including site address, duty holder contacts, and client declaration)
Schedule 2 — Welfare facilities required on all construction sites (toilets, washing facilities, drinking water, changing rooms, rest facilities)
Schedule 3 — Specific high-risk construction work that the construction phase plan must address
Schedule 4 — Work requiring safety signs on existing structures and services
Schedule 5 — Duty holders to whom Chapter 1 of Part 3 applies (legacy domestic duty holder provision)
Schedule 6 — Requirements for reports of inspections
Schedule 7 — Revocations

CDM 2015 and the Building Safety Act 2022

The Building Safety Act 2022 sits alongside CDM 2015 and extends its scope for higher-risk buildings (defined by section 65(1) of the Act as buildings in England that are at least 18 metres in height or have at least 7 storeys and contain at least 2 residential units). The Building Safety Act creates additional competence requirements for principal designers and principal contractors on higher-risk buildings, introduces a new regulatory body (the Building Safety Regulator), and imposes a gateway process requiring regulatory approval at design and construction stages before work can proceed.

CDM 2015 continues to apply to higher-risk buildings. The Building Safety Act imposes additional requirements on top of CDM — it does not replace them.

Sources

This guide is for informational purposes and does not constitute legal advice. For project-specific CDM compliance questions, consult a qualified health and safety professional.

Last reviewed: 12 August 2026