A fit-out contractor started a three-storey refurbishment last spring believing the architect held the principal designer role. The architect believed the client’s project manager had appointed a CDM consultant. The consultant had quoted for it and had never been instructed. Under the CDM regulations that gap already had an answer, and it was not the comfortable one: where the client makes no written appointment, the client holds the principal designer and principal contractor duties themselves.
The Construction (Design and Management) Regulations 2015, usually shortened to CDM 2015, are the principal health and safety regulations for construction work in Great Britain. They came into force on 6 April 2015, replacing CDM 2007, and the Health and Safety Executive enforces them. They apply to every construction project, however small. Their method is to place named duties on the people who shape the work as well as on the people holding the tools.
Why put legal duties on clients and designers at all? Because most construction accidents trace back to decisions taken long before anyone arrived on site. A detail that can only be built at height. A material choice that leaves someone a maintenance hazard for the next twenty years. CDM 2015 requires health and safety to be planned, managed and monitored across the whole life of a project, from the first design decision through to handover and eventual demolition.
Which projects do the CDM regulations cover?
All of them. CDM 2015 applies to all construction work in Great Britain, including domestic projects and including work that lasts two days. There is no lower threshold below which the regulations switch off. What changes with the size and shape of a project is how much structure the regulations impose, and that turns on two separate tests.
The first test is whether the project involves, or is reasonably expected to involve, more than one contractor. If it does, the client must appoint a principal designer and a principal contractor in writing. The second test is whether the project is notifiable to the HSE, which depends on duration and person-days rather than on how many firms are on the job.
Those two tests are independent, and confusing them is the most common CDM error there is. A project can be notifiable with a single contractor. A project can involve five contractors and never come near the notification thresholds. Submitting an F10 appoints nobody, and not needing an F10 excuses you from appointing nobody.
Who holds duties under CDM 2015?
Six roles, and one organisation can hold more than one of them. A design-and-build contractor is very often both principal designer and principal contractor, which is perfectly legitimate as long as both appointments exist in writing and both sets of duties are being discharged.
| Duty holder | Who it is | Core responsibility |
|---|---|---|
| Client | Anyone for whom a construction project is carried out | Make suitable arrangements for managing the project, and ensure they are maintained |
| Domestic client | An individual having work done on their own home, not in connection with a business | Duties normally pass to the contractor or principal contractor |
| Principal designer | Designer appointed in writing to control the pre-construction phase | Plan, manage and monitor pre-construction health and safety; prepare the health and safety file |
| Designer | Anyone who prepares or modifies a design, including specifiers and temporary works designers | Eliminate foreseeable risks through design; provide information about residual risks |
| Principal contractor | Contractor appointed in writing to control the construction phase | Plan, manage and monitor construction; draw up and maintain the construction phase plan |
| Contractor | Anyone who carries out or manages construction work | Plan, manage and monitor their own work; cooperate with the principal contractor |
Workers are not a duty holder in the same sense, but CDM places duties on them too: to take care of their own and others’ health and safety, cooperate, and report anything that looks likely to endanger someone.
The client’s list is longer than most clients expect
Under CDM 2015 the commercial client carries more weight than under any previous version of the regulations, and cannot hand the duties away by hiring a consultant. The client must:
- Make suitable arrangements for managing the project so it can be carried out without risks to health or safety, and maintain and review those arrangements.
- Satisfy themselves that everyone they appoint has the skills, knowledge, experience and organisational capability to do the job.
- Provide pre-construction information to every designer and contractor, as early as possible.
- Where more than one contractor is involved, appoint a principal designer and a principal contractor in writing. If the client fails to appoint, the client takes on those duties themselves.
- Ensure the principal contractor has drawn up a construction phase plan before the site is set up.
- Ensure suitable welfare facilities are provided from the outset.
- Ensure the health and safety file is prepared, and keep it available after handover.
Underneath all of that sits the allocation of time and money, which is the duty clients discharge worst. If the programme cannot be built safely at the price and in the window the client has set, the client has to move one of them.
What changes when the client is a homeowner
A domestic client is someone having construction work done on their own home, or the home of a family member, where the work is not connected to a business. Their CDM duties do not disappear. They transfer.
On a single-contractor project the client’s duties pass to the contractor. Where there is more than one contractor they pass to the principal contractor instead. They can pass to the principal designer, but only where there is a written agreement to that effect.
If you work in the domestic market, read that again. You are routinely carrying the client’s duties alongside your own, and the homeowner has no reason to know it.
What the principal designer is on the hook for
Pre-construction. The principal designer plans, manages and monitors health and safety while the design is still moving: identifying foreseeable risks, getting them designed out where that is possible, controlling whatever is left, checking that the other designers are complying with their duties, and passing the right information through to the principal contractor. They also prepare the health and safety file and hand it over.
The role has to be filled by a designer, meaning an organisation or individual with control over the pre-construction phase, and the client appoints in writing whenever more than one contractor is involved. For the full duty list, the appointment mechanics and the difference from the Building Regulations role, see our guide to the principal designer under CDM 2015.
What the principal contractor owns once the site is set up
The construction phase, and the plan that governs it. The principal contractor draws up and maintains the construction phase plan, organises cooperation between the contractors on site, makes sure inductions happen, secures the site against unauthorised access, provides welfare facilities and consults the workforce.
This is also the point where the CDM paper trail stops being paperwork and starts being evidence. The risk assessments and method statements, the point of work risk assessments and the site diary are what show, eighteen months later, that the plan was followed. Full detail: our guide to the principal contractor under CDM 2015.
Designers and contractors still carry their own duties
Every designer has duties under CDM, not only the one wearing the principal designer badge. When preparing or modifying a design, a designer must take account of the general principles of prevention and eliminate foreseeable risks so far as is reasonably practicable. Where a risk cannot be eliminated they must reduce or control it, and they must provide information about any residual risk to the client, the principal designer and the principal contractor. That catches specifiers and temporary works designers, who frequently do not think of themselves as designers at all.
Every contractor must plan, manage and monitor their own work, satisfy themselves that anyone they employ or engage has the necessary skills, knowledge, training and experience, and comply with directions from the principal designer or principal contractor. On a single-contractor project, the contractor also draws up the construction phase plan.
When does the HSE need telling?
Notification is a size test, nothing more. A project must be notified to the HSE if the construction work is scheduled to:
- last longer than 30 working days and have more than 20 workers working simultaneously at any point in the project; or
- exceed 500 person days.
The client makes the notification, using form F10, before the construction phase begins. It changes nobody’s duties. It does not trigger the appointment of a principal designer or a principal contractor either, because that trigger is the more-than-one-contractor test, and the two get muddled constantly. See our full guide to the F10 notification and the notifiability thresholds.
Take a strip-out package: eleven working days, nine operatives, with a licensed asbestos removal contractor and a demolition contractor both on site. Not notifiable, nowhere near it. It still needs a principal designer and a principal contractor appointed in writing, and it still needs a construction phase plan before anyone lifts a floor tile.
The CDM document set, and who owns each part
| Document | Who produces it | When | Purpose |
|---|---|---|---|
| Pre-construction information | Client (assisted by principal designer) | As early as possible, before design and tender | Tells designers and contractors what is already known about the site and the project |
| F10 notification | Client | Before construction starts, if notifiable | Tells HSE the project exists |
| Construction phase plan | Principal contractor (or the contractor on single-contractor jobs) | Before the site is set up; kept live throughout | Sets out how construction will be managed safely |
| Health and safety file | Principal designer, handed to client | Built through the project; issued at handover | Information for anyone doing future work on the structure |
| RAMS | Each contractor | Before the activity starts | Task-level risk assessment and method statement |
| POWRA | The work team | At the point of work | Last check that conditions match the plan |
Two details in that table get missed. The health and safety file is only required where more than one contractor is involved. And if the principal designer’s appointment ends before the project does, responsibility for the file passes to the principal contractor, who hands it to the client at the end.
Concept to handover, in order
- Concept and brief. Client sets up the management arrangements and starts assembling pre-construction information, testing capability before anyone is appointed.
- Design. Principal designer appointed in writing; designers eliminate and reduce risk; residual risk information recorded.
- Pre-construction. F10 submitted if notifiable; principal contractor appointed; construction phase plan drawn up before site set-up.
- Construction. Plan managed and monitored; RAMS, inductions, POWRAs and site records maintained; welfare provided throughout.
- Handover. Health and safety file completed and issued to the client, who keeps it available for future work.
Two different roles are called principal designer
Since October 2023 there has been a second principal designer role, created by the Building Safety Act 2022 regime under the Building Regulations. It shares a name with the CDM role and very little else. Appointing one does not appoint the other.
The CDM principal designer is concerned with health and safety risk across the project: how the thing gets built, and then maintained, without hurting anybody. The Building Regulations principal designer is concerned with whether the design complies with the Building Regulations themselves. The same organisation may hold both roles, and often does, but the appointments are distinct and should be documented separately. On projects starting now, assuming one covers the other is a live source of gaps.
What does non-compliance cost?
The HSE enforces CDM. It can issue improvement and prohibition notices, recover its costs through the fee for intervention regime, and prosecute. Sentencing for health and safety offences in Great Britain is turnover-linked, so penalties for larger organisations can be substantial, and individuals can be prosecuted personally.
The commercial exposure usually lands sooner than the regulatory one, though. A prohibition notice stops work. Missing or contradictory documentation weakens your position in any argument about delay or defect, because the CDM record and the commercial record are largely the same documents read by different people.
Where software takes some of the load
CDM compliance is rarely a knowledge problem. Most contractors know perfectly well what a construction phase plan has to contain. The problem is that the document set is interdependent and permanently a fortnight out of date. The same site facts get retyped into the pre-construction information, the plan, the RAMS and the file. Then the design moves, some of those documents get updated, and the rest quietly do not.
Take the connection detail that changes in week six because the steel supplier substituted a section. The revised drawing lands and gets issued. The method statement for that lift still describes the old sequence, and it will carry on describing it until an auditor or an accident makes somebody read it.
That is the shape of problem assistive AI suits. It can draft first versions of routine documents from information the business already holds, hold one consistent set of site facts across the whole document family, flag where a design change has left a method statement stale, and turn a year of site records into something searchable in seconds. What it cannot do is take on the duty. A competent person still reviews and owns every document that leaves the business, and the duty holder named in the appointment is still the duty holder afterwards.
For the wider view of which construction applications are proven and which are still emerging, see our piece on AI in construction. For demolition, our operational efficiency work with demolition contractors covers how this compliance load plays out on strip-out and demolition packages, including Section 61 applications.
Questions we get asked about CDM 2015
Do the CDM Regulations apply to small jobs?
Yes, to all of them. Size and duration change nothing about whether CDM applies. What they change is whether a principal designer and principal contractor must be appointed, and whether the project is notifiable.
Who appoints the principal designer and principal contractor?
The client, in writing, whenever a project involves more than one contractor. Skip it and the client is treated as holding those duties.
Is a construction phase plan needed on every project?
Every project, before site set-up. On a single-contractor job the contractor draws it up. Otherwise it belongs to the principal contractor.
What is the difference between a notifiable project and one that needs a principal contractor?
Size versus number of firms. Notifiability is the size test: over 30 working days with more than 20 workers on site at once, or over 500 person days. The principal designer and principal contractor appointments are triggered by the project involving more than one contractor. Neither test implies the other, and plenty of projects satisfy one without the other.
Who keeps the health and safety file?
The client, after handover. The principal designer prepares it and hands it over, and the client keeps it available to anyone who needs it for future work on the structure. If the principal designer’s appointment ends before the project does, the principal contractor takes the file on.
Do CDM duties apply to demolition?
Yes. Demolition is construction work under CDM 2015, and the regulations add a requirement of their own: the arrangements for demolition or dismantling must be recorded in writing before the work begins.
Most contractors reading this are already compliant. They are just compliant expensively, with the same site information keyed in four times and documents revised a fortnight after the change that made them wrong. That is an operating model problem wearing a compliance badge, and it is fixable.
Book a discovery call if you want to work out where your pre-construction and site documentation is costing you time.