CDM Regulations 2015: What Builders Need to Know
A plain-English guide to CDM 2015 regulations for builders. Covers duty holder roles, notification thresholds, the F10 form, and common mistakes.
What Are the CDM Regulations?
The Construction (Design and Management) Regulations 2015 — CDM 2015 for short — are the main set of regulations for managing health, safety, and welfare on construction projects in the UK. They replaced CDM 2007 and apply to every construction project, no matter how small.
That last point is worth repeating. There's a common myth that CDM only applies to big commercial jobs. It doesn't. A kitchen extension, a loft conversion, even a bathroom refit — CDM applies to all of them. What changes is the extent of the duties and whether the project needs to be notified to the HSE.
The Five Duty Holders
CDM 2015 defines five duty holder roles. On a large project, these will be different people or organisations. On a smaller job, one person might wear several hats.
1. Client
The person or organisation the work is being done for. On domestic projects, this is the homeowner. On commercial projects, it's the business commissioning the work.
Key duties:
- Make suitable arrangements for managing the project
- Make sure other duty holders are appointed
- Allow sufficient time and resources for the work
- Provide pre-construction information (what you know about the site — asbestos surveys, existing drawings, underground services, etc.)
- Ensure a construction phase plan is in place before work starts
- Ensure a health and safety file is prepared and kept
Important for domestic clients: Homeowners are technically the client, but their duties automatically pass to the contractor (or principal contractor if there's more than one contractor). The homeowner doesn't need to do anything themselves — but the contractor needs to pick up those duties.
2. Principal Designer
The designer with control over the pre-construction phase. Usually the architect or lead design consultant. Must be appointed on projects with more than one contractor.
Key duties:
- Plan, manage, and monitor the pre-construction phase
- Identify, eliminate, and control foreseeable risks in the design
- Ensure designers cooperate and coordinate their work
- Prepare and update the health and safety file
- Provide pre-construction information to designers and contractors
3. Principal Contractor
The contractor with control over the construction phase. Must be appointed on projects with more than one contractor.
Key duties:
- Plan, manage, and monitor the construction phase
- Prepare the construction phase plan
- Organise cooperation between contractors
- Ensure suitable site inductions are provided
- Prevent unauthorised access to the site
- Ensure welfare facilities are provided
4. Designer
Anyone who prepares or modifies a design for a building or structure, including drawings, design details, specifications, and bills of quantities.
Key duties:
- Not start work unless the client is aware of their duties
- Consider the health and safety implications of their designs
- Eliminate hazards where possible, reduce risks where not
- Provide information about remaining risks to other duty holders
5. Contractor
Anyone who carries out or manages construction work. This includes subcontractors.
Key duties:
- Not start work unless the client is aware of their duties and a construction phase plan is in place
- Plan, manage, and monitor their own work and their workers' work
- Ensure adequate welfare facilities
- Provide information, instruction, and training to workers
- Not employ or appoint someone who isn't competent
- Comply with the construction phase plan
When Do You Need to Notify the HSE?
Not every project needs notifying. The thresholds are:
- The project will last longer than 30 working days AND have more than 20 workers on site at any one time, OR
- The project exceeds 500 person-days of construction work
If either threshold is met, the client (or principal contractor on domestic projects) must notify the HSE using the F10 form before construction begins.
The F10 Form
The F10 is a notification form submitted online through the HSE's website. It includes:
- Project address and description
- Client details
- Principal designer and principal contractor details
- Planned start date and expected duration
- Estimated maximum number of workers on site
It's straightforward to fill in and takes about 10 minutes. You can update it if details change during the project.
Use the CDM Checker to work out whether your project needs notification and which duty holders need appointing.
The Construction Phase Plan
Every project needs a construction phase plan (CPP) before work starts on site. On single-contractor projects, the contractor prepares it. On multi-contractor projects, the principal contractor is responsible.
The plan doesn't need to be a 50-page document. For a small domestic job, it might be two or three pages. It should cover:
- Description of the project
- Management arrangements (who's responsible for what)
- Arrangements for controlling significant site risks
- The health and safety file (what needs to go in it)
Common risks that should be addressed:
- Working at height (scaffolding, ladders, roof work)
- Excavations (trenches, foundations)
- Services (gas, electric, water — especially buried services)
- Asbestos (any building built before 2000)
- Manual handling
- Noise and vibration
- Fire
- Traffic management
For the specific risk assessments, a RAMS Generator can help you build method statements and risk assessments quickly.
Common CDM Mistakes
1. Thinking CDM Doesn't Apply to Small Jobs
It does. Every construction project in the UK falls under CDM 2015. The level of paperwork and formality should be proportionate to the risk, but the duties still apply.
2. Not Having a Construction Phase Plan
This is the most common failing on domestic projects. Even a straightforward extension needs a basic plan before tools hit the ground. Building control inspectors are increasingly asking to see them.
3. Confusing "Competence" with "Qualifications"
CDM 2015 replaced the old "competence" requirement with a requirement for "skills, knowledge, training, and experience." You don't need a specific qualification — but you do need to demonstrate that you and your workers can do the job safely.
4. Ignoring Pre-Construction Information
The client must provide what they know about the site. If there's an asbestos survey, hand it over. If you know about underground services, share that information. Contractors turning up blind to a site's hazards is exactly what CDM is trying to prevent.
5. No Health and Safety File
The health and safety file is a record of information needed for future construction work on the building. It should include as-built drawings, details of hidden services, structural details, and any hazardous materials. The client must keep this file and pass it on if the building is sold.
6. Not Appointing a Principal Designer or Principal Contractor
If your project has more than one contractor (including subcontractors), you need both a principal designer and a principal contractor. Many projects get this wrong by treating subcontractors as if they're part of the main contractor's organisation.
Penalties
The HSE can and does prosecute for CDM failures. Penalties include:
- Improvement notices — requiring you to fix a problem within a set time
- Prohibition notices — stopping work immediately until a problem is resolved
- Prosecution — fines are unlimited for all offences, and individuals can face up to two years in prison for the most serious breaches
- Fee for Intervention (FFI) — if the HSE finds a material breach during an inspection, they charge you £174 per hour (2025/26 rate) for the time spent dealing with it
In practice, the HSE tends to focus on higher-risk projects. But they do inspect domestic jobs, especially after accidents. And if someone is seriously injured or killed, a lack of CDM compliance will make things significantly worse.
If an incident does occur on site, use the Incident Report tool to document it properly — RIDDOR reporting requirements apply to many construction injuries.
Quick Summary
- CDM 2015 applies to every construction project — no exceptions
- Five duty holders: client, principal designer, principal contractor, designer, contractor
- Principal designer and principal contractor must be appointed when there's more than one contractor
- Notify the HSE (F10 form) if the project exceeds 30 days with 20+ workers, or 500 person-days
- Every project needs a construction phase plan before work starts
- Keep it proportionate — a small extension doesn't need the same paperwork as a tower block
- Use the CDM Checker to see what applies to your project