For small builders and main contractors (UK, focus on England/Wales)
Last reviewed: March 2026
CDM 2015 is not just for big sites with cranes. It applies to every construction job, including Mrs Jones's kitchen and your one-off loft. On domestic work, most of the client's legal duties slide straight onto you by default.
This page is about the minimum you need to have your head around so CDM doesn't sneak up and bite you.
1. What CDM actually is (in builder terms)
CDM 2015 = Construction (Design and Management) Regulations 2015 - the health and safety law that sits over how construction projects are planned, managed and run.
It's about:
- Who is responsible for planning the job safely.
- How risks are managed and coordinated between trades.
- Making sure workers have information, training and welfare.
On domestic jobs, the legal players are:
- Domestic client - the homeowner.
- Principal designer (PD) - whoever is in charge of pre-construction design and risk (often the architect/technician, sometimes you).
- Principal contractor (PC) - whoever is in charge of running the job on site (almost always you on a multi-trade domestic job).
2. When you become "principal contractor" (PC)
Short answer: if you're running a job with more than one trade on it, you are the principal contractor whether anyone calls you that or not.
Examples:
- Loft conversion: you bring in joiners, roofers, sparks, plumber, plasterer → you're the PC.
- Kitchen extension: groundworkers, brickies, roofer, sparks, plumber, kitchen fitter → you're the PC.
- House refurb: strip-out, studwork, plaster, M&E, joinery → you're the PC.
On domestic jobs, the homeowner's client duties usually default to the contractor/PC unless there's a written agreement putting them on a PD instead.
So if no one has said otherwise in writing, assume:
- You're principal contractor.
- You may, in practice, also be the principal designer if you're doing design-and-build or making design calls on site.
3. What being principal contractor actually means
Forget the legal waffle; this is the core of your CDM duties as PC on a domestic job:
Plan the work
- Break the job into phases.
- Decide the sequence so trades aren't tripping over each other.
- Identify the nasty bits: work at height, temporary works, structural changes, asbestos risk, confined spaces, services.
Have a basic Construction Phase Plan (CPP)
For domestic work, this can be short - but it must exist.
It should say:
- What the job is and who's involved.
- Site rules (PPE, smoking, housekeeping, welfare).
- Main risks and how you're controlling them.
- Emergency arrangements (fire, first aid, hospital).
On a kitchen extension, this can be a few pages - doesn't need to be a glossy 40-page manual.
Coordinate and supervise trades
- Make sure every subbie knows the risks and controls before they start.
- Don't have multiple trades working dangerously on top of each other (e.g. demo overhead while spark is wiring below).
- Stop work if someone is clearly doing something unsafe.
Make sure welfare is in place
- Toilets, hand-washing, drinking water, somewhere to eat, somewhere to dry clothes - even on domestic jobs.
- "Use the client's loo and sink" can be acceptable, but it needs to be agreed and workable.
Inductions and briefings
- Every worker should know: access/egress, fire points, first aid, site rules, key hazards.
- On a small job, a 10-minute chat and a signed induction sheet is enough - as long as it actually happens.
Keep a basic paper trail
- RAMS or at least method statements for high-risk work (roof, steel installs, temp works, lifting).
- Copies of insurances, tickets/cards (e.g. for plant, asbestos awareness), and any design calcs.
- Record of inductions/toolbox talks and any incidents/near misses.
None of this needs to be corporate. It just needs to be real: you've thought about how people could get hurt on this job and how you're controlling it.
4. What the "principal designer" bit means for you
On paper, the principal designer (PD) is whoever controls the pre-construction design and needs to:
- Plan, manage and monitor the design to minimise risk.
- Pass information about residual risks to you as PC and to the client.
On domestic work, that might be:
- The architect/technician (if they're appointed as PD).
- You, if there's no formal PD and you're making structural/layout/cut-and-carve decisions.
Practically, if you're acting as PD in any way:
- Don't design in obvious stupid risks (e.g. inaccessible plant, maintenance with no safe access, crazy temporary works).
- Ask for calcs/details where you're not qualified (engineer for steels, temporary works, basements).
- Pass key info on to whoever owns the place at the end: where steels are, what walls are structural, what's in the floor/roof build-up.
5. What CDM wants from you on a small domestic job
Think "minimum decent standard", not gold-plate:
On a typical loft/extension
- A simple CPP in your job folder - not generic waffle, but tailored to that address.
- Site induction form and a quick site rules sheet everyone signs.
- Risk-based method statements for the hairy tasks:
- Demolition/strip-out.
- Temporary propping when you take walls out.
- Roof work/scaff.
- Lifting in steels.
- Working near live services.
- Evidence of welfare (client's facilities or hired in).
- Names and contact details for PC, PD (if any), and the client.
- At the end: key info bundled into the handover pack (drawings, steel schedules, manufacturers' info, certs) - this doubles as your "health and safety file" for most domestic jobs.
If the job is bigger or commercial/communal (HMOs, flats, shops), you scale this up - but the principles are the same.
6. Where small builders usually get caught out
Recurring themes:
"CDM doesn't apply to domestic"
Wrong. Since 2015, it absolutely does; the domestic client's duties just transfer to you and/or the PD.
No CPP at all
HSE checks and some BCs now ask to see it, especially after accidents.
No welfare
Lads on site all day with no proper loo/wash point is a straight CDM breach.
No coordination of trades
Everyone turns up at once, zero planning, near misses all over the place.
No record of anything
When something goes wrong, you've got nothing to show you ever thought about safety.
The HSE's case studies for small builders are full of jobs exactly like yours where a bit of planning would have prevented serious injuries.
7. How this interacts with Building Regs and insurers
CDM is separate from Building Regs:
- BC care about compliance with Parts A-S; they're not there to police CDM.
- HSE care about CDM; they don't sign off Building Regs.
But:
- If someone is hurt and HSE turn up, they'll look at your CDM compliance: CPP, inductions, welfare, method statements.
- If there's a claim, your insurer will be a lot more helpful if you can show you took CDM seriously (plan, site rules, RAMS, evidence of control).
So even on domestic jobs, a bit of CDM paperwork is not "box-ticking"; it's you protecting your lads, your client and your business.
8. Practical minimum to bake into every job
If you want the "no drama" level of CDM on all domestic work:
Before you start
- Agree who is PD (if anyone) and confirm you're PC in writing.
- Do a short, job-specific CPP and risk register.
- Sort welfare (client's loo or hired unit) and basic site rules.
When you start
- Induct every worker; get signatures.
- Brief key risks and controls; keep method statements handy.
While you're on site
- Keep the site tidy.
- Manage trades and stop obviously unsafe work.
- Update the plan if the job changes significantly.
At the end
- Hand over as-built info, certs and any residual risk notes with your usual completion pack.
Do that, and for 95% of small domestic projects you'll be in a far better place than most of your competition.
This page is a general guide for small builders and main contractors. It doesn't replace the CDM Regulations 2015, HSE guidance, or legal advice. Always check the latest HSE CDM guidance, your contracts, and (for bigger or higher-risk jobs) speak to a competent health and safety advisor. SiteKiln does not provide legal, financial or tax advice. All content is for general information purposes only. Always seek professional advice for your specific situation.
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Working in Wales? The building rules are different. See our Working in Wales guides.
Working in Scotland? Building standards work differently. See our Working in Scotland guides.
Working in Northern Ireland? The system uses Technical Booklets. See our Working in Northern Ireland guides.
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