NOTE Nº 0635 · REV A

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 · 3 min read · Published 29 August 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: act as the de facto contractor and the coordination duties can land back on 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 doesn’t quite happen.

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.
More than one contractor → the principal contractor (the one in overall control, which your contract should name) carries them, and a principal designer carries the design-phase coordination where there’s meaningful design work.

You don’t file anything to make this happen; it’s the legal default. 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 (the HSE publishes a simple template; the CITB app version is common), not a lever-arch file. A principal contractor who’s never heard of one is telling you something;
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;
designers (architects, engineers) weighing buildability and safety in their design, the reason awkward maintenance-access questions get asked at drawing stage.

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

The trap: becoming the contractor 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, is drifting toward being a contractor in fact, with the coordination duties that follow. HSE guidance is pragmatic about householders, and prosecution of homeowners is vanishingly rare outside genuine recklessness, but 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.