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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.

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 most relevant duties are those of the contractor and, on domestic jobs, the additional duties that transfer from the client.

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 CDM client duties themselves. Instead, those duties transfer automatically to the contractor. If there is one contractor on the job, all client duties transfer to you. If there are multiple contractors and a principal contractor has been appointed, the duties transfer to the principal contractor.

In practice, this means that on a domestic job, you cannot say “that is the homeowner’s responsibility.” You are responsible for:

  • Producing the Construction Phase Plan before work starts
  • Ensuring adequate welfare facilities are in place
  • Making sure the project is managed safely throughout
  • Providing site-specific inductions for all workers
  • Notifying the HSE if the project is notifiable (rare for domestic work)

The domestic client can choose to take on client duties themselves by making a written declaration, but this is extremely rare. Assume the duties are yours unless you have that declaration in writing.

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 your project meets either threshold, you must notify the HSE before the construction phase begins by submitting an F10 form. Most domestic projects carried out by sole traders or small firms will not come close to these thresholds, so notification is unlikely to be required. However, you still need a Construction Phase Plan regardless.

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 — you just review and submit.

The F10 form

The F10 is the form you use to notify the Health and Safety Executive (HSE) about a notifiable construction project. It must be submitted 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. It is not a complicated form, but it does require you to have certain 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 domestic projects these transfer to the contractor.

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. They 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 take on the duties that would otherwise fall to a principal contractor, including producing the CPP.

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

Common questions small builders ask about CDM 2015.

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 client duties themselves. Instead, those duties transfer automatically to the contractor (if there is one contractor) or the principal contractor (if there are multiple contractors). This means you, as the builder, take on the responsibility that would normally sit with the client.

Do I need to notify the HSE?

You only need to notify the HSE if your project is ‘notifiable.’ A project is notifiable if the construction phase will last longer than 30 working days and have more than 20 workers on site at any one time, or exceed 500 person-days in total. If your project does not meet either of these thresholds, you do not need to notify the HSE. Most domestic projects for sole traders and small builders will not be notifiable. However, you still need a Construction Phase Plan regardless of whether the project is notifiable or not. If your project is notifiable, you must submit an F10 notification to the HSE before the construction phase begins.

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.

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Related guides

What is a Construction Phase Plan?

A plain-English guide to CPPs for UK builders.

What is RAMS?

A builder’s guide to Risk Assessments and Method Statements.

Site Inductions Guide

What to cover, how to run one, and why digital beats paper.

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