CDM 2015 for Small Builders: Who's Responsible for What
The Construction (Design and Management) Regulations 2015 — CDM 2015 — are the main set of regulations governing health and safety on construction projects in Great Britain. They replaced CDM 2007, and a key change was removing the old "CDM co-ordinator" role and widening the duties so they apply to all construction work, regardless of project size.
If you're a small builder, sole trader, or subcontractor, these regulations apply to you. Full stop. There's no exemption for small projects, domestic work, or one-person operations. The full text is on legislation.gov.uk — that's the primary source and the one you should bookmark.
This guide breaks down the CDM 2015 responsibilities in plain English so you know exactly where you stand.
The five duty holder roles
CDM 2015 creates five duty holder roles. On a large commercial project, these might be five different organisations. On a small domestic job, one or two people might wear several hats at once.
Client
The client is whoever the construction work is being carried out for (Regulation 2(1)). On a home extension, that's the homeowner. On a commercial fit-out, it's the business commissioning the work.
Clients must make sure the project is set up so it can be carried out safely. Under Regulation 4, they need to make suitable arrangements for managing the project, allocate enough time and resources, and make sure relevant information (like existing asbestos surveys or structural drawings) gets passed to the people who need it.
For domestic clients — homeowners or anyone having work done on their own home — the duties under Regulations 4 and 6 normally transfer to the contractor or principal contractor (Regulation 7). So if you're a builder working directly for a homeowner, you're likely picking up those client duties too.
Designer
A designer is anyone who prepares or modifies designs for a building, product, or system relating to construction work (Regulation 2(1)). This doesn't just mean architects. If you're a plumber designing a heating layout, or an electrician planning a distribution board, you're acting as a designer.
Designers must not start work unless the client is aware of their duties (Regulation 9). When preparing designs, they must eliminate foreseeable risks where possible, reduce risks that can't be eliminated, and provide information about remaining risks (Regulation 9(3)).
Principal designer
On projects with more than one contractor, the client must appoint a principal designer (Regulation 5(1)(a)). This person plans, manages, monitors, and coordinates the pre-construction phase to make sure health and safety risks are addressed in the design. On smaller projects with only one contractor, no principal designer appointment is needed.
Contractor
This is the role most small builders and tradespeople fall into. A contractor is any person who carries out, manages, or controls construction work (Regulation 2(1)). That includes sole traders, partnerships, and limited companies of any size.
Contractor duties sit under Regulation 15, and we'll go through them in detail below.
Principal contractor
On multi-contractor projects, the client must also appoint a principal contractor (Regulation 5(1)(b)). The principal contractor plans, manages, monitors, and coordinates the construction phase. They draw up the construction phase plan, organise cooperation between contractors, and make sure everyone on site has the right inductions.
If no principal contractor is appointed on a project that needs one, the contractor takes on those duties by default (Regulation 5(3)).
When CDM 2015 applies
All construction work in Great Britain. That means every loft conversion, kitchen refit, re-roof, rewire, garden wall, and driveway. Regulation 3 makes this clear: the regulations apply to construction work as defined in Regulation 2 — and that definition is broad, covering building, alteration, fitting-out, commissioning, repair, upkeep, redecoration, demolition, and more.
The common misconception is that CDM only applies to big sites with cranes and hard hats. It doesn't. If you're doing construction work, CDM 2015 applies.
Notifiable vs non-notifiable projects
Not every project needs to be formally notified to the HSE, but CDM duties still apply either way.
A project becomes notifiable under Regulation 6(1) when it meets either of these thresholds:
- The construction phase will last longer than 30 working days and have more than 20 workers on site at any one time, OR
- The construction phase will exceed 500 person-days
If your project is notifiable, the client (or the principal designer on their behalf) must give notice to the HSE before the construction phase begins.
Most small builder projects — extensions, renovations, domestic work — fall below these thresholds. But that changes nothing about your contractor duties.
What a small builder actually has to do (Regulation 15)
Here's the practical bit. Regulation 15 sets out contractor duties, and for a small builder or sole trader, this is your core compliance checklist:
- Plan, manage, and monitor your work so it's carried out without risks to health and safety, so far as is reasonably practicable (Reg 15(1)).
- Have (or make arrangements for) adequate supervision, instructions, and information for workers, including any you engage as subcontractors.
- Do not start work on a project unless the client is aware of their duties and there is a construction phase plan in place for the project (Reg 15(4) and Reg 15(5)).
- Provide every worker under your control with appropriate site inductions, information, and training (Reg 15(8)).
- Ensure suitable welfare facilities are available before work starts (Reg 15(11), cross-referencing Schedule 2).
- Prepare a written construction phase plan if you are the only contractor on the project (Reg 15(10)) — because on a single-contractor project, the contractor must prepare the plan.
- Carry out risk assessments and produce method statements — your RAMS — covering the specific hazards of the work you're doing. For a walkthrough of how to set these up, see our risk assessment template guide for construction.
If you're using subcontractors, their CDM obligations don't replace yours. You still need to manage and coordinate the work. That said, subs have their own duties too — we've covered whether subcontractors need their own RAMS separately.
Common CDM mistakes small builders make
"CDM doesn't apply to me — I'm too small." It does. There is no size exemption. Regulation 3 applies CDM to all construction work.
"The homeowner is the client, so it's their problem." On domestic projects, Regulation 7 transfers client duties to the contractor. You can't hand responsibility back to a homeowner who has no construction expertise.
"I don't need a construction phase plan for a two-week bathroom refit." If you're the only contractor on the project, Regulation 15(10) says you prepare the construction phase plan. It doesn't need to be a fifty-page document — it needs to be proportionate to the risks — but it needs to exist.
"Risk assessments are optional for small jobs." They aren't. Your duty to plan, manage, and monitor under Regulation 15(1) includes identifying hazards and managing risks. A risk assessment is how you demonstrate that.
"I told my subcontractors to sort their own safety." Coordination is a contractor duty. You can't subcontract away your management obligations.
Quick reference: CDM 2015 roles and responsibilities
| Role | Who they are (typical small project) | Key duties |
|---|---|---|
| Client | Homeowner or person commissioning work | Make suitable arrangements, provide pre-construction information, ensure welfare facilities (duties transfer to contractor on domestic projects via Reg 7) |
| Designer | Anyone preparing/modifying designs — architect, engineer, or you if you're designing layouts | Eliminate and reduce foreseeable risks in designs, provide information on remaining risks (Reg 9) |
| Principal Designer | Appointed on multi-contractor projects only | Coordinate pre-construction health and safety, ensure designers comply (Reg 11) |
| Contractor | You — the builder, tradesperson, or sub | Plan, manage, monitor work; ensure competence and training; prepare construction phase plan if sole contractor; provide welfare (Reg 15) |
| Principal Contractor | Appointed on multi-contractor projects only | Coordinate the construction phase, produce construction phase plan, manage site rules and inductions (Reg 13) |
Important note
This guide explains CDM 2015 duties in plain English for general awareness. It is not legal advice. CDM 2015 applies in Great Britain (England, Wales, and Scotland) — Northern Ireland has separate regulations (CDM (NI) 2016). For the definitive text, refer to the full CDM 2015 regulations on legislation.gov.uk. If you need advice on your specific legal obligations, consult a qualified health and safety professional.
Keeping on top of it
CDM 2015 compliance boils down to knowing your role on each project, documenting your risk management, and coordinating properly with everyone else involved. For most small builders, that means having solid RAMS for every job and a proportionate construction phase plan.
If you're spending too long wrestling with Word templates and copying the same boilerplate hazards from job to job, that's exactly the problem we built TradeRAMS to solve. It generates structured RAMS documents tailored to your trade and the specific job. We're rolling out access through a waitlist — you can join the TradeRAMS waitlist to get early access when it opens.