If you’re planning to build a new house, extend your home, or convert a building into a dwelling, you need to understand how the Construction (Design and Management) Regulations 2015 (CDM Regulations) affect your project. These regulations are designed to ensure health, safety, and welfare during construction work and apply to all construction projects in the UK, regardless of size or complexity.
This article explores how the CDM Regulations impact homeowners and developers, the role of the Principal Designer, and the requirements for notifying the Health and Safety Executive (HSE).
1. How Do CDM Regulations Affect Domestic Projects?
CDM applies to all construction work, including new builds, extensions, and conversions. If you’re hiring contractors (builders, architects, or surveyors) to work on your project, you have responsibilities under the regulations.
However, if you’re a domestic client (someone building or renovating their home for personal use), your legal duties are transferred to:
The contractor (if there is only one).
The Principal Contractor and Principal Designer (if there is more than one contractor).
This means that while you don’t need to manage health and safety yourself, you must ensure that competent professionals are appointed.
For commercial clients (property developers, landlords, or businesses), the duties under CDM cannot be transferred, and they must take an active role in compliance.
2. Who is the Principal Designer?
The Principal Designer (PD) is a key duty holder under CDM 2015. They are responsible for health and safety during the design phase and ensuring that risks are managed before construction begins.
When is a Principal Designer Required?
If your project involves more than one contractor (e.g., a builder and an electrician), you must appoint a Principal Designer.
If you fail to do so, the client assumes the role by default, meaning legal responsibility falls on you.
3. What Are the Duties of the Principal Designer?
The Principal Designer’s duties include:
Pre-Construction Phase (Design Stage)
Plan, manage, and monitor health and safety during the design phase.
Identify and eliminate risks that can be removed at the design stage.
Communicate risks to contractors and ensure safe methods are planned.
Ensure that designers follow their CDM duties.
Assist the client in understanding their obligations.
Construction Phase (On-Site)
Collaborate with the Principal Contractor to ensure safety on-site.
Update the health and safety file with relevant information.
Ensure any design changes do not introduce new, unmanaged risks.
Post-Construction
Provide the client with a Health and Safety File, containing essential safety information for future use (e.g., maintenance, renovations, or demolitions).
4. When Must the HSE Be Notified?
Some projects require formal notification to the Health and Safety Executive (HSE) before work begins.
A project must be notified if it:
Lasts more than 30 working days AND has 20 or more workers on site at any one time.
Involves more than 500 person-days of construction work.
If your project meets these criteria, you must submit an F10 Notification Form to the HSE. The form includes details such as:
The client’s details.
The Principal Designer and Principal Contractor’s details.
A brief description of the project.
The expected start and end date.
The maximum number of workers on-site at any time.
If your project does not meet these thresholds, it is not notifiable, but CDM Regulations still apply.
5. Key Takeaways for Homeowners and Developers
CDM Regulations apply to all construction work, including new builds, extensions, and conversions.
If you’re a domestic client, CDM duties transfer to your contractor or Principal Designer/Principal Contractor.
A Principal Designer must be appointed if there is more than one contractor.
The Principal Designer ensures health and safety in the design phase and hands over a Health and Safety File at project completion.
HSE notification is required for projects exceeding 30 days with 20+ workers or 500 person-days of work.
By ensuring compliance with CDM 2015, you protect not just workers on-site but also future occupants of your home. Always appoint competent professionals to manage these responsibilities and maintain health and safety standards throughout your project.
For more guidance, consult the HSE’s official CDM regulations documentation or speak to a qualified Principal Designer.
Jbh Architectural Services 
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