CDM 2015 guide
What is CDM? The Construction (Design and Management) Regulations 2015
A plain-English guide to CDM 2015 — what it means, who it applies to, and what you actually need to do as a builder or contractor working in the UK.
TL;DR
CDM means the Construction (Design and Management) Regulations 2015. They apply to construction work in Great Britain, including domestic jobs. In plain English: the job must be planned, the risks managed, the right people appointed when needed, and a Construction Phase Plan prepared before work starts.
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What does CDM stand for?
CDM stands for the Construction (Design and Management) Regulations 2015. These are the main health and safety regulations for the UK construction industry. They apply to all construction work in Great Britain — from a bathroom refit to a multi-storey office block. There are no exemptions based on project size or value.
CDM 2015 replaced CDM 2007 on 6 April 2015 and brought several changes — most notably extending the regulations to cover domestic projects and simplifying the duty holder structure. The full text is published by the Health and Safety Executive (HSE), along with guidance documents L153 and INDG411.
Who does CDM apply to?
CDM 2015 applies to every construction project in Great Britain — commercial and domestic. If you are doing construction work of any kind, CDM applies to you. This includes sole traders, self-employed subcontractors, small builders, and large contractors. The regulations cover new builds, extensions, refurbishments, demolition, maintenance, and repair work.
The extent of what you need to do depends on your role and the scale of the project. But the basic principle is the same for everyone: construction work must be planned, managed, and monitored to ensure it is carried out safely.
The CDM duty holders
CDM 2015 defines six duty holder roles. On a small domestic job, one person might fill several roles. On a large commercial project, each role is usually a separate appointment.
Client
The person or organisation the work is being done for. On commercial projects, the client must make suitable arrangements for managing the project, ensure adequate welfare facilities, and appoint a principal designer and principal contractor when there is more than one contractor. The client does not need to manage health and safety directly, but they must make sure someone competent is doing it.
Domestic Client
A homeowner or occupier having work done on their own home. Domestic clients have the same duties as commercial clients under CDM 2015, but those duties are automatically passed away from them — by default to the contractor if there is only one contractor (or to the principal contractor if there is more than one contractor), or, where there is more than one contractor, instead to a principal designer under a written agreement. Producing the Construction Phase Plan is a separate duty: the only contractor prepares it on a single-contractor project, while the principal contractor prepares it where there is more than one contractor.
Designer
Anyone who prepares or modifies a design for a building or structure. This includes architects, structural engineers, building services engineers, and interior designers — but also contractors who design temporary works or change a design on site. Designers must eliminate, reduce, or control foreseeable risks through their design choices.
Principal Designer
On projects with more than one contractor, the client must appoint a principal designer to plan, manage, monitor, and coordinate the pre-construction phase. The principal designer ensures that designers cooperate and that health and safety risks are addressed in the design. On domestic projects with one contractor, this role is not required.
Principal Contractor
On projects with more than one contractor, the client must appoint a principal contractor to plan, manage, monitor, and coordinate the construction phase. Where there is more than one contractor, the principal contractor must produce the Construction Phase Plan, ensure cooperation between contractors, and manage site safety. On domestic projects, the client's own duties (not the principal contractor's) transfer away from them by default — to the contractor if there is only one contractor or to the principal contractor if there is more than one contractor — or, where there is more than one contractor, instead to a principal designer under a written agreement.
Contractor
Anyone carrying out construction work, including sole traders, subcontractors, and self-employed tradespeople. Every contractor must plan, manage, and monitor their own work to ensure it is carried out safely. They must cooperate with the principal contractor (if there is one), provide information and training to workers, and not start work unless satisfied that adequate welfare facilities are in place.
When do you need to notify the HSE?
Not every project needs to be notified to the HSE. A project is notifiable if it meets either of these thresholds:
- The project will last more than 30 working days AND will have more than 20 workers on site at any one time, OR
- The project will exceed 500 person-days of construction work.
If a project is notifiable, the commercial client holds the regulation 6 duty. On domestic work it passes to the only contractor on a single-contractor project, or the principal contractor on a multi-contractor project, unless a principal designer agrees in writing to fulfil it. The duty holder, or someone acting on their behalf, submits an F10 notification form to HSE at the time regulation 6 requires. The Site Book checks notifiability and pre-fills the form from your project data.
Even if your project is not notifiable, you still need to comply with all other CDM 2015 requirements — including producing a Construction Phase Plan, carrying out risk assessments, and ensuring adequate welfare facilities.
Domestic vs commercial projects
One of the biggest changes in CDM 2015 was extending the regulations to domestic projects. Under CDM 2007, domestic clients were largely exempt. Now, the same duties apply — but with an important difference in how they are allocated.
On a domestic project (work done on a home that is not connected to a business), the homeowner’s CDM duties are automatically transferred away from them. If there is only one contractor, they take on the regulation 4 and 6 client duties. If there are multiple contractors, the duties transfer to the principal contractor — or, where there is more than one contractor, instead to a principal designer, if the domestic client and the principal designer agree in writing that the principal designer will take the duties on.
On a commercial project, the client retains their own duties and must actively manage them — including appointing a principal designer and principal contractor when there is more than one contractor on site.
In practice, the main builder may be the only contractor or the principal contractor on domestic work, but the project structure determines which duties it holds. The only contractor prepares the CPP on a single-contractor job; the principal contractor does so where there is more than one contractor.
How CDM affects small builders
If you are a sole trader or small builder working mostly on domestic projects, CDM 2015 means you need to:
- Produce a Construction Phase Plan (CPP) for every project — proportionate to the risks
- Carry out risk assessments and produce RAMS for work with significant hazards
- Ensure adequate welfare facilities are available on site — toilets, washing, rest areas
- Provide information, instruction, and training to anyone working on site
- Check whether the project is notifiable and who holds the F10 duty
- Cooperate with any other contractors or designers on the project
The good news is that CDM is proportionate. A domestic extension does not need the same level of documentation as a multi-storey commercial build. A 1-2 page Lightweight CPP and a site-specific RAMS are usually sufficient for a small domestic job. The Site Book is designed specifically for this — creating proportionate documentation structured around CDM 2015 requirements for competent review, without the enterprise overhead.
Common misconceptions about CDM
Myth: “CDM only applies to big commercial jobs”
Reality: CDM 2015 applies to ALL construction work in Great Britain — including domestic extensions, loft conversions, bathroom refits, and kitchen installations. There are no exemptions based on project size.
Myth: “I don’t need a CPP for domestic work”
Reality: Every construction project needs a Construction Phase Plan. On domestic projects where you are the sole contractor, the duties transfer to you. The CPP does not need to be a 20-page document — a proportionate plan covering the key risks is sufficient.
Myth: “The homeowner is responsible for CDM”
Reality: On domestic projects, the homeowner’s CDM duties are automatically transferred away from them — by default to the contractor if only one contractor is involved (or to the principal contractor if multiple contractors are involved), or, where there is more than one contractor, instead to a principal designer if the homeowner agrees this in writing. Checking competence is not a duty the homeowner keeps either: regulation 8(3) puts the duty to take reasonable steps to satisfy yourself that an appointed designer or contractor has the right skills, knowledge and experience on whoever makes the appointment, and regulation 8(7) hands it, so far as it would otherwise fall on a domestic client, to whoever holds the client duties under regulation 7(1). Where there is more than one contractor, the written-agreement route does still need the principal designer to agree to it in writing. The HSE encourages homeowners to ask about a firm’s health and safety track record, but that is good practice rather than a CDM duty. Neither route changes who does the day-to-day work: that responsibility is always the builder’s.
Myth: “CDM is just paperwork”
Reality: CDM is about planning and managing work safely. The documentation — the CPP, RAMS, and other records — is the evidence that you have done the thinking. But the purpose is to prevent accidents, not to produce paper.
Myth: “Only notifiable projects need CDM compliance”
Reality: All projects need CDM compliance. Notifiable projects (those lasting more than 30 working days with more than 20 workers at any one time, or exceeding 500 person-days) have the additional requirement of notifying the HSE via an F10 form. But every project — notifiable or not — must comply with CDM 2015.
CDM 2015 at a glance — key points and watchouts for small builders
Pros
- Clear legal framework: every duty is written down in one document (HSE L153) and free to download.
- Risk-based and proportionate: CDM explicitly allows a lightweight Construction Phase Plan on domestic jobs.
- Six defined duty holders cover every construction role — no ambiguity over who is responsible for what.
- Free HSE guidance plus worked examples are available at hse.gov.uk/construction/cdm/2015/.
Cons
- Applies to ALL construction work in Great Britain — even a single-day kitchen refit needs a CPP.
- On domestic projects with only one contractor, the homeowner’s duties pass to that contractor by default — often surprises sole traders.
- Notifiable projects (>30 working days with >20 workers at any one time, OR >500 person-days) need an F10 submission before work starts.
- Principal contractors carry the enforcement risk — sub-contractors cannot hide behind the PC if controls break down.
| Duty holder | Commercial project | Domestic project |
|---|---|---|
| Client | Arranges project + appoints PD/PC | Duties pass to only contractor (one contractor) or PC (more than one) by default; written-agreement PD alternative where there is more than one contractor |
| Principal Designer | Required if >1 contractor | Not appointed on single-contractor jobs. Where there is more than one contractor, can take the regulation 4(1)–(7) and 6 client duties under a written agreement (reg 7(1)(c)) |
| Principal Contractor | Required if >1 contractor | Required if >1 contractor; contractor in control is deemed PC if no appointment |
| Contractor | Plans own work safely | Same; also holds client duties if it is the only contractor or the principal contractor by default |
| Designer | Designs out foreseeable risk | Same |
| Worker | Cooperates, reports hazards | Same |
“The Construction (Design and Management) Regulations 2015 (CDM 2015) are the main set of regulations for managing the health, safety and welfare of construction projects.”
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Frequently asked questions
What does CDM stand for?
CDM stands for the Construction (Design and Management) Regulations. The current version is CDM 2015, which came into force on 6 April 2015 and replaced CDM 2007. The regulations set out the duties of everyone involved in a construction project — from the client and designers through to contractors and workers — to ensure that health, safety, and welfare are properly managed throughout the project.
Does CDM apply to domestic work?
Yes. CDM 2015 applies to all construction work in Great Britain, including work on domestic properties. The key difference is that on domestic projects, the client’s duties are automatically transferred away from the client — by default to the contractor if there is only one contractor (or to the principal contractor if there are multiple contractors), or, where there is more than one contractor, instead to a principal designer if there is a written agreement to that effect. If there is only one contractor, that contractor prepares the construction phase plan under regulation 15; if there is more than one contractor, the principal contractor prepares it under regulation 12. Preparing the plan is not one of the client duties regulation 7 moves.
What is an F10?
An F10 is required if a project is scheduled to last longer than 30 working days and have more than 20 workers on site simultaneously, or to exceed 500 person-days. The commercial client holds the regulation 6 duty. On domestic work it passes to the only contractor on a single-contractor project, or the principal contractor on a multi-contractor project, unless a principal designer agrees in writing to fulfil it. The duty holder, or someone acting on their behalf, submits the project details to HSE.
Who is responsible for CDM on a domestic project?
On a domestic project with only one contractor, the homeowner’s CDM duties are automatically transferred to that contractor, who takes on the regulation 4 and 6 client duties — including ensuring a construction phase plan is prepared and ensuring adequate welfare facilities. If there are multiple contractors, the client’s duties transfer to the principal contractor — or, where there is more than one contractor, instead to the principal designer if there is a written agreement that they will take the duties on. Writing the plan itself is a separate duty: the only contractor prepares it on a single-contractor project, while the principal contractor prepares it where there is more than one contractor. In practice, the main builder may be the only contractor or the principal contractor, but the project structure determines which duties it holds.
Related guides
CDM 2015 for Small Builders
Your duties under CDM as a sole trader or small builder.
CDM Domestic Client Duties
What builders need to know about domestic projects and CDM.
Principal Contractor Duties
CDM roles explained — principal contractor vs contractor.
F10 Notification
When and how to notify the HSE about your project.
What is a Construction Phase Plan?
Everything you need to know about CPPs.
What is RAMS?
Risk Assessments and Method Statements explained.
CDM paperwork — drafted for your review
The Site Book drafts CPP, RAMS and site documents from your project details, structured around CDM 2015. Your first project is on us.
Sources
- Construction (Design and Management) Regulations 2015 — legislation.gov.uk · Accessed 4 May 2026
- The Construction (Design and Management) Regulations 2015 — HSE · Accessed 4 May 2026
- Planning for construction work — HSE · Accessed 4 May 2026