CDM 2015 for Small Builders: A Plain English Guide

If you're a small builder, sole trader or two-person firm, the Construction (Design and Management) Regulations 2015 affect you more than most people realise. The common assumption — "CDM is for big sites" — has cost a lot of small contractors a lot of money in HSE enforcement notices over the last decade. The good news is that the rules aren't as complicated as the regulation reads. The bad news is that "I'm only doing a kitchen extension" doesn't get you out of any of them.

This guide covers what CDM 2015 requires from a small UK builder, written in plain English with no legal hedging.

Does CDM 2015 apply to your work?

Yes, almost certainly. CDM 2015 applies to all construction work in Great Britain — there is no minimum project size, value or duration. A one-day repair job in a domestic property is covered by CDM. A new-build extension is covered by CDM. Replacing a few roof tiles is covered by CDM.

What changes with project size is which duties apply most heavily, who counts as the principal contractor, and whether you need to notify the HSE. The core duty — to plan, manage and document the work safely — applies to everyone, every time.

The roles you might hold (often more than one)

On a small project, the roles tend to collapse onto one or two people. Here's what each role means in plain terms:

• Client. The person paying for the work. On a domestic job for a homeowner, the homeowner is technically the client, but most of their CDM duties pass to the contractor (you).
• Principal designer. Coordinates safety during the design phase. On a small job with no separate designer, this often defaults to the principal contractor.
• Principal contractor. The contractor in charge of the construction phase. On a job with only one contractor (you), you are the principal contractor by default.
• Contractor. Anyone carrying out construction work. If you're the only firm on site, you're both contractor and principal contractor.

The practical upshot for a small builder running a job alone: you are wearing the principal contractor hat whether you'd planned to or not.

What you actually have to do

Strip out the regulatory language and the duties land in five buckets:

1. Plan the work before you start

You need to think through the hazards, the access, the sequence and the welfare arrangements before the first day on site — not when something goes wrong. For most jobs this lands in your construction phase plan and your RAMS.

A construction phase plan is required for every CDM project, regardless of size. For small jobs it can be short and simple — a couple of pages covering scope, key risks, controls, welfare and emergency arrangements. For a domestic kitchen extension it might run to 4–6 pages. There's no template required by law, but it has to actually cover what's needed.

2. Provide welfare facilities

Toilets, washing facilities, drinking water, somewhere to eat and somewhere to change. On a domestic job this often means using the homeowner's facilities by arrangement — that's allowed, but it has to be agreed in writing as part of the planning. If the homeowner is moving out and there's no running water, you need to provide something.

This is the duty most commonly ignored on small sites and the one most likely to embarrass you if HSE inspectors arrive unannounced.

3. Make sure everyone is competent

You need to be reasonably sure that everyone working on site has the skills, knowledge, training and experience to do their job safely. For your own staff this is straightforward. For subcontractors you bring in (electricians, plumbers, scaffolders) you should be checking their qualifications and asking for evidence — not just taking their word for it.

4. Document the work

RAMS or equivalent. Construction phase plan. F10 notification if applicable (see below). Records of inductions, toolbox talks, equipment inspections. You don't need a filing cabinet — a phone with PDFs in a folder is fine — but you do need to be able to produce these documents if asked.

5. Notify the HSE if the project is notifiable

A project is notifiable if either:

• The construction work is scheduled to last longer than 30 working days AND has more than 20 workers on site at any one time, OR
• The work exceeds 500 person-days in total.

For most small builders, this means the typical extension or refurbishment is not notifiable. But a longer renovation that runs 6+ weeks with multiple trades on site can hit the 500 person-days threshold without you noticing. If your project is notifiable, the F10 notification is the client's duty (in commercial work) or yours (in practice on most domestic jobs because the duty defaults to you).

Domestic clients: the rule that catches everyone out

For most CDM duties on a domestic job, the client's duties pass to the contractor. That sounds helpful — fewer awkward conversations with the homeowner about welfare facilities — but it means you, as the contractor, are responsible for things you might assume the homeowner would handle. If something goes wrong on a domestic job, the HSE is going to be looking at the contractor first.

Practical implications: you need a written agreement with the homeowner covering welfare facilities, access, working hours and any restrictions. You need to think through the risks of working around an occupied home (children, pets, parked cars, deliveries blocking the road). And you need to keep your documentation tighter than you might on a commercial site, because there's no client safety team backing you up.

The five things HSE inspectors actually look for on small sites

From talking to inspectors and reading enforcement notices on the HSE website, the issues that come up most often on small builder sites are:

1. No or inadequate edge protection when working at height — this is the single biggest cause of fatalities in UK construction and the easiest thing to spot from the road.
2. No welfare facilities, particularly on jobs where the homeowner has moved out.
3. Untrained operatives using powered access equipment (MEWPs, scissor lifts) without IPAF cards or evidence of training.
4. Site set-up that endangers the public — unfenced excavations, materials stored on pavements, deliveries blocking shared driveways.
5. No documented planning — no construction phase plan, no RAMS, no risk assessment for the work.

None of these are complicated to fix. All of them get small builders prohibition notices and fines several times a year.

What "good" looks like for a small builder

A small builder doing CDM properly has, for every job:

• A short construction phase plan (2–6 pages) before work starts
• A site-specific RAMS for the work being done
• A written welfare arrangement (even if it's "use of the homeowner's downstairs WC by agreement")
• Evidence of competency for any subcontractors brought in
• Records of any toolbox talks or inductions
• F10 notification if the project hits the thresholds

That's it. It's not a lot of paperwork in absolute terms — the important part is doing it consistently before each job and checking that the arrangements fit the work.

The bit about RAMS specifically

A RAMS is the most-asked-for document under CDM, even though it isn't named in the regulations. Principal contractors expect it. Insurers expect it. Domestic clients increasingly expect it. The reason is that the RAMS is the practical proof you've planned the work — the regulations require the planning, and the RAMS is the evidence.

For a small builder, producing site-specific RAMS for each job is the single most useful piece of CDM documentation you can do. It covers most of your planning duty in one document, it's what principal contractors will ask for, and it's what HSE inspectors will look for first if they turn up.

Related guides

• How to write a RAMS document in the UK — the document CDM effectively requires
• CDM risk assessment template — structured CDM-aligned risk assessments
• Why principal contractors reject RAMS — relevant when you're working as a sub
• How much does a RAMS cost? — what's reasonable to pay
• CDM-structured RAMS generator — produce a CDM-aligned RAMS in minutes