The Construction (Design and Management) Regulations 2015 set out health and safety duties for everyone involved in construction projects in the UK. CDM applies to ALL construction work regardless of size or duration. It defines roles for clients, designers, principal designers, contractors and principal contractors.

When is a project notifiable to the HSE?

A project is notifiable if it will last longer than 30 working days AND have more than 20 workers on site at any one time, OR exceed 500 person days of construction work. Notification is via the F10 form submitted to HSE online before the construction phase begins.

Do domestic projects need CDM compliance?

Yes, CDM 2015 applies to domestic projects. However, domestic clients (homeowners) have their CDM duties automatically transferred to the contractor (single contractor) or principal contractor (multiple contractors). Domestic clients do not need to appoint a principal designer or submit F10 notifications themselves.

When do I need a Principal Designer and Principal Contractor?

A Principal Designer (PD) and Principal Contractor (PC) must be appointed on any project involving more than one contractor. The client makes these appointments. For domestic projects, if no appointment is made, the duties default to the designer/contractor. PD manages pre-construction health and safety; PC manages the construction phase.

What is the F10 notification form?

The F10 is a notification submitted to HSE for notifiable projects. It includes: project description and address, client details, principal designer and principal contractor details, planned start date and duration, estimated maximum number of workers. It must be submitted as soon as practicable before construction begins.

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CDM Compliance Calculator — Duty Holder Requirements

Determine CDM 2015 duties, F10 notification requirements and duty holder appointments based on project value, duration and workforce numbers.

Project type

Project duration

Max workers on site at once

More than one contractor

Includes demolition work

How We Calculate This

This calculator checks CDM 2015 requirements based on project characteristics.

Notification threshold

Projects exceeding 30 days with 20+ workers OR 500+ person days require F10 notification to HSE.

Duty holders

Projects with more than one contractor require a Principal Designer and Principal Contractor. All projects require designers and contractors to fulfil CDM duties.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.