NOTE Nº 0635 · REV B

CDM Regulations 2015 for Domestic Clients Explained

How CDM 2015 applies to home building projects: the automatic transfer of client duties, who is principal contractor, and the DIY project-manager trap.

By The Renovation Notes Team · 4 min read · Published 29 August 2026 · updated within the last month · Sources checked 30 September 2026

Close-up of a skilled worker welding a steel pipe outdoors at a construction site.

In short

CDM 2015 applies to every building project including domestic ones, but as a domestic client your legal duties transfer automatically, to your contractor on single-contractor jobs, or the principal contractor where there are several. The catch is the homeowner who directly hires and coordinates multiple trades: the legal duties still pass to the contractor in control of the work, but nobody may actually be doing the coordinating, and the practical risk sits with you.

Health and safety law on construction sites doesn’t stop at your garden gate, the Construction (Design and Management) Regulations 2015 apply to a loft conversion exactly as they apply to a hospital. The reassuring part is that Parliament knew homeowners aren’t safety professionals and built in an automatic hand-off. The part worth reading carefully is where that hand-off works on paper but not on site.

The automatic transfer

A domestic client, someone commissioning work on their own home, not in the course of business, has their CDM client duties transferred by default:

One contractor on the job → that contractor carries the client duties.¹
More than one contractor → the principal contractor (the one in overall control, which your contract should name) carries them, and a principal designer coordinates the pre-construction phase. If you don’t appoint them, the contractor in control of the construction phase becomes principal contractor and the designer in control of the pre-construction phase becomes principal designer.¹

You don’t file anything to make this happen; it’s the legal default.² Your practical residue is simply choosing competent people, which the vetting process covers anyway, and not obstructing the arrangements they make.

What the duty-holders should be doing

Knowing what good looks like lets you spot its absence:

a construction phase plan for the project: on a domestic extension this is a short, proportionate document, not a lever-arch file, and HSE’s CIS80 leaflet includes a blank template for it (CITB also offers a construction phase plan app), so a principal contractor who’s never heard of one is telling you something;³
site management basics: induction of trades, welfare provision (the toilet question is actually a legal one), scaffold inspections, protecting the public and your family from the works;⁴
designers (architects, engineers) weighing buildability and safety in their design, the reason awkward maintenance-access questions get asked at drawing stage.⁵

Notifiable projects, lasting more than 30 working days with more than 20 workers simultaneously, or exceeding 500 person-days, need an F10 notification to HSE.⁶ Almost no ordinary domestic job reaches this; a very large self-build can.

The trap: running the site yourself

The transfer works because there’s a contractor to transfer to. The homeowner who directly engages the groundworker, brickie, chippie, sparky and plasterer separately, sequences their work, and runs the site, the classic money-saving self-project-manager, still isn’t a contractor in law: CDM defines a contractor as someone who carries out, manages or controls construction work in the course of a business.⁷ The client duties pass instead to whichever contractor is in control of the construction work, but in practice nobody may be coordinating the trades, and you are the one standing in the middle of the site.² The exposure is real when someone is hurt: civil liability doesn’t need HSE’s interest.

If you self-manage, borrow the structure the regulations expect: one written plan of who’s on site when, induction of each trade to the site’s risks, welfare sorted, scaffold from a proper firm with inspection tags, and the discipline not to let trades stack dangerously (sequencing is half of project management anyway). Better still, on anything structural or multi-trade, hire a main contractor and let the transfer do its job, the margin you pay them is partly the price of carrying this.

The practical checklist

Before start on site: principal contractor named in writing where there are multiple trades; construction phase plan seen (two pages is fine); welfare agreed; your neighbours and household warned about the risky phases. During: leave site management to the people holding the duty, the client who rearranges the scaffold is volunteering for it back. CDM is one of those regimes where the compliant path and the sensible path are the same road; the construction law pillar shows where it sits among the rest.

This guide is general information for homeowners in England and Wales, not legal advice.

References (7)

Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

1technicalvery strongThe National Archives, legislation.RN-MEXGZNRegulation 7 of CDM 2015, application to domestic clients. A homeowner's client duties pass automatically to the contractor where there is one contractor, to the principal contractor where there is more than one, or to the principal designer under a written agreement. This is the provision that means a householder does not personally carry CDM duties, and it is also why appointing several trades directly quietly makes somebody the principal contractor.
2technicalvery strongHealth and Safety Executive, guidance.RN-D7GLU7HSE page (updated 7 October 2025) defining a domestic client under CDM 2015 as any individual having construction work done on their own home or a family member's home that is not part of a business. On a single-contractor project the contractor automatically takes on the client's legal duties; where there is more than one contractor the principal contractor takes them on, unless the client makes a written agreement for the designer to act as principal designer.
3technicalvery strongHealth and Safety Executive, guidance.RN-E9A39QHSE's two-page leaflet for small builders on the CDM 2015 construction phase plan, with a blank template, for jobs such as extensions and loft conversions.
4technicalvery strongThe National Archives, guidance.RN-8N9L39Schedule 2 of CDM 2015, the minimum welfare facilities required on construction sites, including toilets, washing facilities and drinking water.
5technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-X9NPARRegulation 9 of CDM 2015 sets what an architect, architectural technologist or engineer must do before drawing anything, and the first duty is the one most homeowners never see performed. Paragraph (1): a designer must not commence work in relation to a project unless satisfied that the client is aware of the duties owed by the client under the Regulations, so a designer who never mentioned CDM to a domestic client is already in breach. Paragraph (2): in preparing or modifying a design the designer must take into account the general principles of prevention and any pre-construction information to eliminate, so far as is reasonably practicable, foreseeable risks to anyone carrying out or liable to be affected by construction work, maintaining or cleaning the structure, or using it as a workplace. Paragraph (3): where risks cannot be eliminated they must be reduced or controlled through the design, with information given to the principal designer and included in the health and safety file. Paragraph (4): the designer must take all reasonable steps to provide sufficient information with the design to help the client, other designers and contractors comply with their own duties.
6technicalvery strongThe National Archives, legislation.RN-3XA3FCRegulation 6 of CDM 2015, notification. A project is notifiable to HSE if the construction work is scheduled to last more than 30 working days with more than 20 workers at any one time, or to exceed 500 person days. Below those thresholds no F10 notification is needed, which is why almost no domestic job is notifiable and why a contractor asking for one on a house extension is usually mistaken.
7technicalvery strongThe National Archives, guidance.RN-VKHGPORegulation 2 of CDM 2015, the definitions, including contractor (someone acting in the course of a business) and domestic client (a client not acting in a business).