In short
CDM 2015 applies to all construction work in Great Britain, including extensions, repairs and refurbishments on people's homes. On a domestic job, the homeowner's client duties pass to the builder if there is one contractor, or to the principal contractor if there is more than one. Every job needs a proportionate construction phase plan and welfare from the first day. Only jobs above set size thresholds need to be notified to HSE.
Example
a kitchen extension
Lee runs a three-person building firm. Ruth asked him to build a kitchen extension on her house. An electrician, a plasterer and a roofer from other firms would follow Lee's team, so there would be more than one contractor. Lee took on the principal contractor role and Ruth's client duties, and her architect became principal designer. Before starting, Lee wrote a short plan, asked Ruth about asbestos, drains and cables, and agreed his team could use her downstairs toilet. When the water was off, he hired a welfare unit.
An illustrative example, not a real case.
Does CDM apply to work on a home?
Yes. CDM 2015 applies to all construction work, including domestic projects (HSE). What changes is who carries the client duties.
Domestic client, one contractor
- Who carries the client duties
- The contractor, on top of their own duties (regulation 7)
Domestic client, more than one contractor
- Who carries the client duties
- The principal contractor, or the principal designer if there is a written agreement (regulation 7)
Domestic client who appoints no one
- Who carries the client duties
- The contractor in control of the construction phase is principal contractor, and the designer in control of the pre-construction phase is principal designer (regulation 7)
Commercial client, any size of job
- Who carries the client duties
- The client, in full (regulation 4)
What changes with more than one contractor?
If more than one contractor will work on the project at any time, the client must appoint a principal designer and a principal contractor in writing before the construction phase begins (CDM 2015, regulation 5). Count every trade that is a separate business, including self-employed electricians and plasterers. The principal contractor then plans, manages and coordinates the construction phase and draws up the construction phase plan (regulations 12 and 13).
What must a small builder do?
CDM 2015 regulation 15 says every contractor must:
- Make sure the client knows their duties before work starts.
- Plan, manage and monitor the work you and your workers do.
- Use workers who have, or are getting, the right skills, knowledge, training and experience.
- Give workers supervision, information and a site induction, unless the principal contractor has given one.
- Take reasonable steps to keep unauthorised people off site.
- Draw up a construction phase plan before setting up the site, if you are the only contractor.
What welfare is needed from day one?
Welfare must be in place from the start of the job until the end (CDM 2015, regulations 13 and 15 and Schedule 2). On a small site that means:
- Toilets, with washing facilities next to them: running hot and cold, or warm, water, soap and towels.
- Drinking water.
- Somewhere to rest, eat and boil water for a hot drink.
- Somewhere to change, dry and store clothes where the work needs it.
Notification and pre-construction information
- A project is notifiable if the work is scheduled to last longer than 30 working days and have more than 20 workers on site at the same time at any point, or to exceed 500 person days (regulation 6).
- The client notifies HSE on form F10. On a domestic job this passes to the builder (regulation 7).
- Pre-construction information is what the client knows or can reasonably find out about hazards, such as asbestos, drains and buried cables. It must be given to designers and contractors as soon as practicable (regulation 4).
Common questions
Do I need a construction phase plan for a small job?
Yes. The only contractor or the principal contractor must draw one up before setting up the site (CDM 2015, regulations 12 and 15). A short, simple plan is usually enough, and CITB's free CDM Wizard app can help.
Can builders use the homeowner's toilet?
Yes, if the homeowner agrees and the toilet and washing facilities are available whenever the workers are on site. Agree it before work starts, and plan for when the bathroom or kitchen is out of use.
Can a builder also be the principal designer?
Yes, if the builder does or arranges the design work, is in control of the pre-construction phase and has the skills, knowledge and experience for the role (HSE).
How NXT-HSE can help
NXT-HSE can help you work out who holds which CDM duties on a job and develop a proportionate construction phase plan. NXT-HSE also offers online CDM training.
Sources
- CDM 2015 on legislation.gov.uk
- HSE: CDM 2015 frequently asked questions
- HSE: domestic clients, roles and responsibilities
- HSE: welfare on construction sites
- HSE: Managing health and safety in construction (L153)
- CITB: about CDM 2015
Sources checked 27 September 2026 against current Health and Safety Executive guidance and legislation. This guide is general information, not legal advice; your legal duties stay with your business.