Construction compliance guide
CDM 2015 Explained for Small Builders & Sole Traders
The Construction Design and Management Regulations 2015, explained without the jargon. What it is, what you need to do, and how it applies to your day-to-day work.
TL;DR
The Construction Design and Management Regulations 2015, explained without the jargon. What it is, what you need to do, and how it applies to your day-to-day work.
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What is CDM 2015?
CDM 2015 stands for the Construction (Design and Management) Regulations 2015. It is the main piece of UK legislation governing health and safety on construction projects, as published by the Health and Safety Executive, and it applies to virtually all construction work in Great Britain — from a one-day bathroom refit to a multi-year commercial development. The CITB also provides guidance and training resources for builders working under CDM.
The regulations replaced the earlier CDM 2007 and were designed to simplify the framework while extending it to cover domestic projects properly for the first time. Before CDM 2015, domestic work fell into a grey area. Now, the rules are clear: if you are doing construction work, CDM applies.
CDM 2015 sets out duties for everyone involved in a construction project: clients, designers, principal designers, principal contractors, contractors, and workers. For small builders and sole traders, the contractor duties are especially relevant. On domestic jobs, client duties also transfer under regulation 7.
Your duties as a contractor
Under CDM 2015, every contractor — including sole traders — has four core duties:
Plan
You must plan your work to ensure it can be carried out safely. This means thinking about the risks before you start, not making it up as you go. For most projects, this planning is captured in your Construction Phase Plan (CPP) and your Risk Assessments and Method Statements (RAMS).
Manage
You must manage the work so that it is carried out without risks to health and safety, so far as is reasonably practicable. This includes making sure workers have the right training, equipment is in good condition, and welfare facilities are available.
Monitor
You must monitor your work to make sure the plan is being followed and safety standards are being maintained. This does not mean standing around with a clipboard — it means keeping an eye on things, checking that controls are in place, and acting quickly when something is not right.
Coordinate
If you are working alongside other contractors, you must cooperate with them and coordinate your work to avoid creating risks for each other. Even if you are not the principal contractor, you have a duty to work safely alongside others on site.
These duties apply regardless of whether you are a principal contractor, the only contractor, or a subcontractor. The scope of what you need to do scales with the size and complexity of the project, but the fundamental obligations are the same.
Domestic client rules
This is one of the most important things to understand if you work on domestic projects. Under CDM 2015, a domestic client is a homeowner having construction work done on their own home that is not connected to a business.
Domestic clients do not have to carry out the regulation 4(1)–(7) and regulation 6 client duties themselves. Instead, those duties transfer automatically away from them. By default, if there is one contractor on the job, the regulation 4 and 6 client duties transfer to that contractor. If there are multiple contractors and a principal contractor has been appointed, the duties transfer to the principal contractor instead. Where there is more than one contractor, a domestic client can also make a written agreement with a principal designer to transfer those duties instead of the default arrangement — including the duty to notify the HSE. There is no equivalent duty-transfer agreement for a principal contractor — though, like a principal designer, a principal contractor must still be appointed in writing on a project with more than one contractor, under regulation 5. If the client never makes that appointment on a job with more than one contractor, regulation 7(2) deems whichever contractor is in control of the construction phase to be the principal contractor instead — a sole contractor instead holds the duties directly, with no principal contractor role to deem.
On a domestic job, first identify whether you are the only contractor, the principal contractor, or a contractor working under one. Across those roles, builders may need to:
- CPP responsibility as the only contractor on a single-contractor project or the principal contractor on a multi-contractor project.
- Ensuring adequate welfare facilities are in place.
- Safe management throughout the project.
- Providing suitable inductions to workers under your control, unless the principal contractor already has.
- Notifying the HSE if the project is notifiable and the domestic client duties sit with you.
Check which role you hold and who carries the client duties before work starts. There is no route under CDM 2015 for a domestic client to simply declare that they are keeping the duties themselves — the only way the default allocation above changes is a written agreement with a principal designer where there is more than one contractor (see above).
What ‘notifiable’ means
A construction project is ‘notifiable’ under CDM 2015 if it meets either of these thresholds:
Threshold 1
The construction phase will last longer than 30 working days and have more than 20 workers on site at any one time.
Threshold 2
The project will exceed 500 person-days in total. That is the number of workers multiplied by the number of days they work.
If a project meets either threshold, the regulation 6 duty holder must notify HSE as soon as practicable before the construction phase begins. The commercial client holds that duty. On a domestic project, it passes to the contractor where there is only one contractor, or to the principal contractor where there is more than one contractor, unless a principal designer agrees in writing to fulfil it. Every construction project still needs a Construction Phase Plan.
The Site Book checks your project details automatically and tells you whether your project is notifiable. If it is, the F10 form is pre-filled from your project data for the duty holder, or someone acting on their behalf, to review and submit.
The F10 form
The F10 is the form the regulation 6 duty holder, or someone acting on their behalf, uses to notify the Health and Safety Executive about a notifiable project. It must be submitted as soon as practicable before the construction phase begins.
The F10 contains information about:
- The client — name, address, contact details
- The principal designer — name, organisation, contact details
- The principal contractor — name, organisation, contact details
- The project — site address, description of work, expected start and end dates
- The number of workers expected on site at any one time
- The planned duration of the construction phase
The F10 is submitted electronically through the HSE website. Whoever submits it needs the project details to hand. The Site Book pre-fills the F10 from your project data, so you are not looking up information or filling in the same details twice.
Key CDM terms explained simply
CDM 2015 uses specific terms that can be confusing if you have not come across them before. Here is what they actually mean:
Client
The person or organisation paying for the construction work. On domestic jobs, this is the homeowner. On commercial jobs, it is usually the business or developer commissioning the project. The client has duties under CDM, but on a domestic job with only one contractor these transfer to that contractor by default. Where there is more than one contractor they pass to the principal contractor, or, where there is more than one contractor, to a principal designer under a written agreement.
Principal designer
The designer with control over the pre-construction phase of the project. Their job is to plan, manage, and monitor the design work to make sure health and safety risks are identified and managed from the outset. On projects with only one contractor, there is no legal requirement to appoint a principal designer, though the client may choose to.
Principal contractor
The contractor with overall responsibility for the construction phase when there is more than one contractor on the project. On a project with more than one contractor, the principal contractor must produce and maintain the Construction Phase Plan, coordinate all contractors on site, and ensure site-wide health and safety arrangements are in place. If there is only one contractor, there is no principal contractor — you are the ‘only contractor.’
Contractor
Anyone who carries out, manages, or controls construction work. This includes sole traders, small firms, and subcontractors. Every contractor has duties under CDM regardless of their size or the size of the project.
Only contractor
This is not an official CDM term, but it is widely used. It describes the situation where there is only one contractor on a project — no other firms, no subcontractors. On domestic jobs, this is the most common scenario. As the only contractor, you produce the CPP under regulation 15.
Worker
Anyone carrying out construction work on the project, including employees, self-employed individuals, and agency workers. Workers have their own duties under CDM: they must cooperate with others, report anything dangerous, and follow the site rules set out in the CPP.
Frequently asked questions
Does CDM apply to small jobs?
Yes. CDM 2015 applies to all construction work in Great Britain, regardless of the size of the project. There is no minimum value, no minimum duration, and no exemption for small jobs. A one-day bathroom refit is covered by CDM just as much as a multi-million-pound commercial development. The scale of what you need to do is proportionate — a small domestic job needs a short, simple Construction Phase Plan, not a 50-page document — but the legal obligation to plan, manage, and monitor health and safety applies from the smallest job upwards.
Am I a principal contractor?
You are only a principal contractor if there is more than one contractor working on the project. The principal contractor is the contractor with overall responsibility for the construction phase when multiple firms are involved. If you are the only contractor on a project — which is common on domestic jobs — you are the ‘only contractor,’ not the principal contractor. Your duties are similar but slightly simpler: you must produce a Construction Phase Plan, manage health and safety on site, and ensure any workers you bring on have suitable inductions and training. The distinction matters because certain CDM duties (such as coordinating subcontractors and ensuring their compliance) only apply to principal contractors.
What is a domestic client under CDM?
A domestic client is a person who has construction work carried out on their own home, or the home of a family member, where the work is not done in connection with a business. A homeowner having an extension built is a domestic client. A landlord having work done on a rental property as part of their letting business is not a domestic client — they are a commercial client. The key feature of domestic clients under CDM 2015 is that they do not have to carry out the regulation 4(1)–(7) and regulation 6 client duties themselves. Instead, those duties transfer automatically away from the client — by default to the contractor (if there is one contractor) or 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. By default, the only contractor takes those duties where there is one contractor, while the principal contractor takes them where there is more than one.
Do I need to notify the HSE?
An F10 is required only if the 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 a domestic project, the F10 duty passes to the contractor where there is only one contractor; where there is more than one contractor it passes to the principal contractor, or, where there is more than one contractor, to the principal designer if there is a written agreement to that effect. Whoever holds the duty must notify HSE as soon as practicable before construction begins. Every construction project still needs a Construction Phase Plan.
What’s the difference between CDM and COSHH?
CDM and COSHH are different sets of regulations that cover different aspects of health and safety. CDM 2015 (the Construction Design and Management Regulations) is the overarching framework for managing health and safety on construction projects. It covers everything from project planning and Construction Phase Plans to site inductions and incident reporting. COSHH (the Control of Substances Hazardous to Health Regulations 2002) specifically covers the use, handling, and storage of hazardous substances — such as cement, adhesives, solvents, paints, silica dust, and asbestos. COSHH applies across all industries, not just construction. On a construction site, you may need to comply with both: CDM for the overall project management, and COSHH for any hazardous substances you are using or storing on site. The Site Book handles both — your COSHH assessments feed into your CPP, site induction, and emergency plan automatically.
CDM 2015 for small builders — key points and watchouts
Pros
- Same four core duties (plan, manage, monitor, coordinate) apply whether you are a one-person band or a mid-sized firm.
- Scale is proportionate: a small domestic job needs a short, targeted Construction Phase Plan — not enterprise paperwork.
- Free HSE guidance (L153, INDG411) and HSE templates are readily available and aimed directly at small builders.
- CDM is your shield if something goes wrong: a competently written CPP and RAMS demonstrate due diligence.
Cons
- On domestic jobs with one contractor, client duties pass to that contractor by default; with more than one contractor, they pass to the principal contractor unless a PD agrees in writing.
- Every project needs a Construction Phase Plan, including a single-day kitchen refit — no exemptions based on size.
- 'Only contractor' and 'principal contractor' are not the same legal role — getting the distinction wrong misallocates duties.
- F10 applies if a project is scheduled for more than 30 working days and over 20 workers simultaneously, or more than 500 person-days.
| Duty | Only contractor | Principal contractor |
|---|---|---|
| Produce Construction Phase Plan | Yes (proportionate) | Yes (formal, coordinated) |
| Manage site safety day-to-day | Yes | Yes |
| Coordinate other contractors | N/A — no others on site | Yes (mandatory) |
| Ensure welfare facilities | Yes | Yes |
| Site-specific induction | For workers under its control (regs 15(8)–(9)) | Ensures a suitable induction (>1 contractor, reg 13(4)(a)) |
| Submit/display F10 if notifiable | On a domestic project with one contractor, that contractor holds the F10 duty under reg 7(1)(a) — there is no PD to take it by written agreement; commercial: client holds | On a domestic project with more than one contractor, the PC holds the F10 duty unless a PD agrees in writing; commercial: client retains it when the PC acts on its behalf |
| Maintain H&S file | No statutory file on a single-contractor project | On a multi-contractor project, only if the principal designer's appointment ends before completion |
“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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Sources
- Construction (Design and Management) Regulations 2015 — legislation.gov.uk · Accessed 17 April 2026
- CDM 2015 for small domestic projects — HSE · Accessed 17 April 2026