The Construction (Design and Management) Regulations 2015, usually just called CDM, apply to every construction project in Great Britain, from a one-day bathroom refit to a new hospital. There is no minimum size. Small contractors are often told they "need to be CDM compliant" by a client or main contractor, without anyone explaining what that means on a Tuesday morning on a small job.
This is the plain-English version: who the duty holders are and which one you are, what a contractor actually has to do, when a project must be notified to HSE, how to write a construction phase plan that fits on a few pages, what changes when the client is a homeowner, and the mistakes that cause trouble.
A note on scope: CDM 2015 covers England, Scotland and Wales. Northern Ireland has its own, very similar regulations (CDM (Northern Ireland) 2016). The official detail is in HSE's free guidance, L153, Managing health and safety in construction. Where this guide simplifies, L153 is the place to check, and for anything that matters on a specific job, confirm with your client, the principal contractor or a competent health and safety adviser.
What counts as construction work
CDM's definition is wide. It covers building, alteration, conversion, fitting out, renovation, repair, redecoration and maintenance; demolition; installing, maintaining or removing services such as electrical, gas, water, heating and telecoms; site clearance and excavation; and assembling prefabricated elements.
So a painter, an electrician rewiring an office and a shopfitter on a weekend fit-out are all doing construction work, and so is much of a facilities contractor's planned and reactive maintenance.
Who is who: the duty holders
CDM gives duties to seven groups. One organisation can hold more than one role, and on small jobs it often does.
| Duty holder | Who it is | Core job under CDM |
|---|---|---|
| Client | The organisation or person the project is for, in the course of a business | Make suitable arrangements for managing the project, with enough time and resources; provide pre-construction information; appoint a principal designer and principal contractor where needed; notify HSE if notifiable |
| Domestic client | Someone having work done on their own or a family member's home, not as a business | Duties pass to the contractor or principal contractor (see below) |
| Principal designer | A designer appointed when there is more than one contractor | Plan, manage and coordinate health and safety in the pre-construction phase; help gather pre-construction information; prepare the health and safety file |
| Designer | Anyone who prepares or modifies a design, or instructs others to | Eliminate, reduce or control foreseeable risks through the design, and pass on information about the risks that remain |
| Principal contractor | A contractor appointed when there is more than one contractor | Plan, manage and coordinate the construction phase; draw up the construction phase plan; organise inductions, site security and welfare |
| Contractor | Anyone who carries out, manages or controls construction work | Plan, manage and monitor their own work and workers; cooperate; follow the principal contractor's directions and site rules |
| Workers | The people doing the work | Cooperate, report anything likely to endanger themselves or others, work safely |
Three points trip people up.
You can be a designer without calling yourself one. If you design an electrical layout, specify a temporary support, produce drawings for a design-and-build extension or choose the fixings for a heavy item, you have designer duties for that part of the work.
Principal designer and principal contractor are triggered by the number of contractors, not by notification. The client must appoint both in writing where there is, or is likely to be, more than one contractor. A two-week job with a builder and one electrical subcontractor needs both roles, even though it is nowhere near the notification threshold. If a commercial client doesn't appoint them, the client has to carry out those duties itself.
"Contractor" includes subcontractors and the self-employed. A two-person firm working for a main contractor has contractor duties.
A note on the Building Safety Act
Since October 2023, building regulations in England have had their own dutyholder roles under the Building Safety Act 2022, which confusingly also include a "principal designer" and "principal contractor". Those roles are about compliance with building regulations, not health and safety on site. One firm is often appointed to both versions of a role, but the duties are separate and appointments should say which is meant. In Wales, or on higher-risk buildings, check the current position with the client or building control.
What a contractor must actually do
In plain terms, CDM expects you to do the following on every job.
- Check the client knows their duties. Don't start work for a commercial client unless you're satisfied they are aware of their CDM duties. A sentence in your quotation pointing them to HSE's client guidance does the job on small work.
- Plan, manage and monitor your own work so it is carried out without risks to health and safety, so far as is reasonably practicable: the order of work, the equipment, the people, and how you'll check it's going to plan.
- Use competent people. Everyone must have, or be in the process of getting, the skills, knowledge, training and experience for their task, with closer supervision while they're learning.
- Give your workers supervision, instructions and information: a site induction if the principal contractor isn't providing one, the hazards and controls for the task, emergency procedures, and who the principal designer and principal contractor are.
- Cooperate and follow the principal contractor's rules where there is one.
- Provide welfare facilities, or make sure they are available, from the start of the work.
- Keep unauthorised people out. Take reasonable steps to prevent access before you start. In an occupied house, that means agreeing which rooms are off limits and securing tools and materials.
- Draw up a construction phase plan when you are the only contractor, before you set up on site. Where there's a principal contractor, give them what they need for theirs, which usually means your risk assessments and method statements (see our guide to RAMS that get approved first time).
None of this is new to a well-run firm. CDM mostly asks you to be able to show you did it.
Competence, in practice
CDM doesn't prescribe particular cards or certificates, but clients and principal contractors need evidence, and they use familiar proxies: SSIP accreditation, a PAS 91 questionnaire, CSCS or equivalent cards, trade qualifications, training records and references from similar jobs. Keep them current and in one place; our post on subcontractor onboarding documents covers what to hold.
When a project must be notified to HSE
A project is notifiable if the construction work is scheduled to:
- last longer than 30 working days and have more than 20 workers working at the same time at any point, or
- exceed 500 person-days.
Notification is made to HSE online using form F10. It is the client's duty, done as soon as practicable before the construction phase begins, and a copy should be displayed on site where workers can read it.
- The first test needs both conditions. The second is a total: as an illustration, 25 people for 21 days is 525 person-days, which is notifiable.
- Notification doesn't change the duties. It is an administrative step. Everything else in this guide applies either way.
- Most small jobs aren't notifiable. A three-week refurbishment with six people on site is nowhere near. It still needs a plan, welfare and competent people.
- On domestic projects, the client duties pass to the contractor or principal contractor, so on the rare domestic job that is notifiable, notifying falls to you.
The construction phase plan, kept short
Every project needs a construction phase plan, whatever its size. The principal contractor writes it; where you are the only contractor, you do, before you set up on site.
It should be proportionate. For a small job, two to four pages is normal. What it can't be is generic: a reviewer, an inspector or your own supervisor should read it and recognise the job.
| Section | What to write | Example for a small job (illustrative) |
|---|---|---|
| Project details | Address, client, the work, start date and duration, key contacts | Kitchen extension at 14 Elm Road; 6 weeks from 3 March; supervisor Sam Patel, 07700 900000 |
| Management | Who is in charge, how work is supervised and checked, how you'll talk to the client | Supervisor on site daily; owner visits weekly; client update every Friday |
| Main risks and controls | The significant hazards for this job and how each is controlled, referencing RAMS | Digging near drains: services located with drawings and a CAT before digging, trench support planned in advance; work at height: scaffold erected and inspected by a scaffolding contractor; dust: on-tool extraction and RPE for cutting |
| Site rules | Hours, PPE, parking, deliveries, keeping the household clear of the work | 8am to 5pm; garden work area fenced off while children are home |
| Welfare | Toilets, washing, drinking water, rest and eating, and where they are | Downstairs toilet and utility sink, agreed with the client in writing; van for breaks |
| Emergencies | First aid, fire, nearest A&E, raising the alarm, how emergency services find the site | First aider and kit in the van; nearest A&E and route named |
| Induction and changes | How workers and visitors are inducted, and how changes are briefed | Everyone inducted on day one; rebriefed if scope changes |
HSE publishes a free construction phase plan template, and it's a fine starting point. The trap is filling it in once and reusing it unchanged. Keep a master version of the parts that don't change (management, standard site rules) and spend your time on the risks, welfare and emergency arrangements for each job.
Review the plan as the work develops. If the scope changes, a new subcontractor arrives, or you find something unexpected such as suspected asbestos or unmapped services, update it and tell the people affected before carrying on.
Welfare: what "suitable" means
CDM sets minimum welfare requirements for every site, from the start of the work. Workers must have access to:
- Toilets, ventilated, lit and kept clean.
- Washing facilities next to them, with running hot and cold or warm water, soap and a way of drying hands.
- Drinking water, with cups where needed.
- Somewhere to change and store clothing where special clothing is worn, with a way to dry wet clothes.
- Somewhere to rest and eat, with seating, tables and a means of boiling water and preparing food.
On short and domestic jobs it is common to agree to use the client's facilities. That can be acceptable, but agree it in advance, write it into the plan, and have a fallback. On an empty building with the water off, or a roadside job, you need portable welfare, and that is a cost to include in your price, not something to sort out on the first morning.
Induction and information flow
Much of CDM is about the right information reaching the right person before it's needed:
- The client provides pre-construction information: asbestos surveys, drawings, known services, access restrictions, and how the building will be occupied during the work.
- Designers pass on significant risks their design couldn't remove, such as a heavy lift or a fragile roof.
- The principal contractor, or the sole contractor, turns that into the plan, site rules and inductions.
- Contractors provide their RAMS and competence evidence and brief their own workers.
- Workers report hazards and changes back up the chain.
- At the end, on projects with more than one contractor, the principal designer compiles the health and safety file for the client's future maintenance and alterations. Contractors supply their part, such as as-built details and hidden hazards.
If you don't receive pre-construction information, ask for it in writing: "Is there an asbestos survey? Are there known services where we're digging?" Asbestos is the big one. On buildings constructed before 2000, don't start intrusive work without knowing what's there.
A site induction for a small job takes ten to fifteen minutes: who is in charge, the main hazards and controls, site rules, welfare, first aid and emergencies, and how to report a problem. Record who was inducted and when. A signed sheet is enough.
Domestic clients
A homeowner having work done on their own home is a domestic client. CDM still applies, but their duties are passed on automatically:
- One contractor: the client duties pass to you.
- More than one contractor: a principal designer and principal contractor are still needed. If the homeowner doesn't appoint them, and most don't, the designer in control of the pre-construction phase is the principal designer and the contractor in control of the construction phase is the principal contractor. The client duties pass to the principal contractor.
- Alternatively, the homeowner can agree in writing for the principal designer to take on the client duties.
So if you're a builder taking on a domestic extension and bringing in your own electrician and plasterer, you are very likely the principal contractor and carrying the client duties as well: the plan, the welfare and, if it's ever needed, the F10.
Explain this to the homeowner briefly. Most have never heard of CDM, and they'll accept a fenced-off area or shared toilet more readily if they understand why.
What this looks like on a small job
An illustrative example. A four-person firm is replacing the windows in a two-storey office for a commercial client, working alone on site over five days.
- Duty holders. Commercial client, one contractor, so no principal designer or principal contractor. The firm has designer duties for any fixings or opening changes it specifies.
- Notification. Four workers for five days is 20 person-days. Not notifiable.
- Before starting. The quotation includes a short note on the client's CDM duties. The firm asks for the asbestos register and which areas will be occupied.
- Plan. Three pages covering the main risks (a tower and a MEWP, glass handling, falling objects over a public footpath, occupied offices), site rules, welfare (office toilets and kitchen, agreed with the facilities manager by email) and emergencies.
- RAMS and competence. Method statements for tower and MEWP use and for glazing removal and installation, tailored to the building; PASMA and IPAF cards and supervisor training checked before day one.
- On site. Induction on the first morning, the footpath coned off with a banksman during lifts, and a short end-of-day check.
That's CDM done properly for a small job: perhaps half a day of preparation, most of it reusable next time.
Common mistakes
- Thinking CDM only applies to big or notifiable projects. It applies to all construction work.
- No construction phase plan because "it's only a week". It can be short, but it has to exist before you start.
- Copy-and-paste plans that name the wrong site or miss the hazards that are actually there.
- Not recognising a role change when a second contractor arrives, especially on domestic jobs.
- Welfare left to chance on empty properties with no water or working toilet.
- No record of inductions or briefings, so there's no evidence they happened.
- Not asking for pre-construction information, then finding asbestos or live services the hard way.
CDM is less about paperwork than about showing you thought before you started. The paperwork is just the evidence.
Where software can help
Because the duties repeat from job to job, approved master versions of your plan sections, RAMS and site rules make each new plan quicker to assemble, expiry tracking stops a lapsed card surfacing on day one, and consistency checks catch a plan that still names last month's site. The judgement about this job's risks stays with a competent person.
Start here
Take your next job and write its construction phase plan using the table above. Keep it to a few pages, make every section specific to that site, and save the parts that didn't change as your master template. Then read the contractor sections of HSE's L153 once, so you know where the detail lives when a client or principal contractor asks.