Choosing and managing subcontractors

In short

Before you appoint a subcontractor, CDM 2015 says you must take reasonable steps to check they have the skills, knowledge, experience and, for a firm, organisational capability to work safely. Keep your checks proportionate to the risk. An SSIP certificate, such as CHAS, shows a firm's arrangements were assessed, but HSE says it is not proof they can manage the risks on your site. You still need to coordinate and check their work.

Example

the flat roof on an extension

Mo runs a small building firm and was principal contractor on a single-storey office extension. The cheapest flat roofing quote came with a CHAS certificate, but its method statement was for a different building and said nothing about edge protection. Mo rang the roofer, Chloe, and asked how her team would stop falls and manage the hot works. Her answers were sound, so he asked for RAMS for this roof, checked her team's training cards and agreed the edge protection. On day one he walked the roof with her supervisor.

An illustrative example, not a real case.

What the law says

Anyone appointing a designer or contractor must take reasonable steps to check they have the skills, knowledge, experience and, for a firm, organisational capability to work safely (CDM 2015, regulation 8).
A contractor must not accept work they cannot do safely, and everyone with a CDM duty must cooperate (regulation 8).
The principal contractor must organise cooperation between contractors and coordinate their work (regulation 13).
Each contractor must plan, manage and monitor their own work, follow the principal contractor's directions and use workers with the right skills, knowledge, training and experience (regulation 15).

Checking competence without drowning in paperwork

HSE says your checks should match the risk and complexity of the job. Ask for what tells you about this job, not a pile of generic documents:

How they will do the job, who will supervise and what the main risks are.
RAMS written for this job and site, not a template.
References or examples of similar work.
Training records and cards for the people who will actually turn up.
Their recent health and safety record, including any enforcement action.
Employers' liability insurance, where the law requires it.

What SSIP and CHAS do and do not prove

Have the firm's basic health and safety arrangements been assessed?
What an SSIP assessment tells you
Yes. SSIP member schemes, such as CHAS, use core criteria approved by HSE.
Can they manage the risks on your site?
What an SSIP assessment tells you
No. HSE says scheme assessment is not proof of this. Check their plans for the job.
Are the workers who turn up competent?
What an SSIP assessment tells you
Not on its own. Check the people, their training and their supervision.
Is it required by law?
What an SSIP assessment tells you
No. It is one way of showing competence, and one SSIP scheme should be enough.

Question	What an SSIP assessment tells you
Have the firm's basic health and safety arrangements been assessed?	Yes. SSIP member schemes, such as CHAS, use core criteria approved by HSE.
Can they manage the risks on your site?	No. HSE says scheme assessment is not proof of this. Check their plans for the job.
Are the workers who turn up competent?	Not on its own. Check the people, their training and their supervision.
Is it required by law?	No. It is one way of showing competence, and one SSIP scheme should be enough.

Cooperate, coordinate and supervise

01
Share
Before they start, give them the site rules, the relevant parts of the construction phase plan and the risks from other trades.
02
Induct
Give everyone a site induction on their first day.
03
Coordinate
Plan the order of trades and talk through the next day's work, especially where trades overlap.
04
Check
Watch the work against the agreed RAMS, and stop it if it becomes unsafe.

What the courts have said

R v Associated Octel Co Ltd [1996] 1 WLR 1543
A contractor's worker was badly burned repairing a tank at Octel's chemical plant during a shutdown. The House of Lords upheld Octel's conviction under section 3 of the Health and Safety at Work etc. Act 1974: work a contractor does as part of your business is still your undertaking, so you must make reasonably practicable arrangements for it to be done safely.

Common questions

Is the main contractor responsible for subcontractors' safety?

Partly. The principal contractor must plan, manage, monitor and coordinate the construction phase (CDM 2015, regulation 13), and each subcontractor must plan, manage and monitor its own work (regulation 15). Duties are shared, not handed over.

Does a CHAS certificate mean a subcontractor is competent?

It shows the firm's health and safety arrangements have been assessed. HSE says this is not proof the firm can manage the risks of your site, so also check their plans and people for the job.

Do small subcontractors need a written health and safety policy?

Businesses with fewer than five employees do not have to write down their policy or risk assessment findings (HSE). Ask smaller firms how they control the risks instead.

How NXT-HSE can help

NXT-HSE can review how you select and monitor subcontractors as part of an audit, and help you prepare for CHAS if your clients ask for it.

Sources

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.

Choosing and managing subcontractors safely.