When Something Goes Wrong on Site: Who's Responsible?

‍‌‌​‌‌​‌​​‌‌​​‌​‌‌‌‌​‌​​‌​‌‌​‌​‌‍# S20. When something goes wrong on site - who's responsible

Responsibility on site is shared, but not equally. The law looks at roles and duties, not just who was holding the tool when it went wrong.

1. THE SHORT VERSION

Health and Safety at Work etc. Act 1974 (HSW Act) puts the main duty on employers to protect workers and others "so far as is reasonably practicable".

CDM 2015 spreads duties across client, principal designer, principal contractor, contractors and workers – each has specific legal jobs.

If something goes wrong, investigators ask: who had the duty and control to prevent this, and did they actually do it?

2. BIG PICTURE: THREE LAYERS OF RESPONSIBILITY

Think of it in three layers:

Employer duties (HSW Act 1974) – your direct employer (the firm that pays you) must provide:

• A safe place of work and safe systems.
• Safe plant, tools and substances.
• Information, instruction, training and supervision.
• Risk assessments and a sensible plan to control risks.

CDM dutyholders on the project – client, principal designer, principal contractor, and other contractors must plan and manage health and safety for the whole job, not just their own bit.

Workers' duties – you must look after your own safety and others', follow training, use PPE, and report problems; you can't just ignore rules.

Liability usually lands heaviest on whoever controlled the risk and failed to manage it, often the employer and principal contractor.

3. WHO'S WHO UNDER CDM 2015 (AND WHAT THEY OWE YOU)

Client Person or organisation having the work done (domestic or commercial). Must make suitable arrangements for managing the project, including enough time and money, and appoint a principal designer and principal contractor where there's more than one contractor.

Principal designer (PD) Leads on health and safety in the design and pre‑construction phase. Must identify and reduce design risks where reasonably practicable and pass information to the principal contractor.

Principal contractor (PC) For projects with more than one contractor, the PC is key. They must:

• Plan, manage, monitor and coordinate health and safety during the construction phase.
• Prepare and implement the construction phase plan.
• Organise cooperation between contractors and coordinate their work.
• Provide site inductions, reasonable steps to prevent unauthorised access, and welfare facilities.
• Consult workers and engage them in safety.

They're in overall control of site safety day‑to‑day.

Contractors (including subbies)

• Plan, manage and monitor their own work so it is carried out safely.
• Make sure workers are competent and have the right supervision and equipment.
• Follow the construction phase plan and cooperate with the principal contractor and others.

Workers

• Must take reasonable care of their own health and safety and of others.
• Follow site rules, training and instructions, use PPE and equipment properly, and report defects or dangers.

So when something goes wrong, HSE will ask: Did each dutyholder do what CDM says they should?

4. WHAT THE HSW ACT 1974 PUTS ON EMPLOYERS (AND ON YOU)

Employer duties (section 2) Employers must, so far as reasonably practicable:

• Provide and maintain safe plant and systems of work.
• Make sure handling, storage and transport of materials/substances are safe.
• Provide information, instruction, training and supervision.
• Maintain a safe place of work with safe access/egress.
• Provide adequate welfare facilities.

They must also have a written health and safety policy and consult workers or reps.

Duty to others (section 3) They must protect others who may be affected by their work – subbies, visitors, members of the public.

Your duties as a worker Workers must:

• Take reasonable care for their own health and safety and for others who may be affected.
• Cooperate with their employer on health and safety (follow rules, use PPE, attend training).

The fact that a worker made a mistake doesn't automatically let an employer or principal contractor off the hook if they failed to train, supervise or control the work properly.

5. WHEN AN ACCIDENT HAPPENS – WHO'S LIKELY IN THE FRAME?

HSE, insurers and lawyers will look at:

• Who controlled the work? (principal contractor, specific contractor, site manager).
• What were the risk assessments and method statements? Were they sensible, and followed?
• Were workers trained and supervised?
• Were the right tools, PPE and welfare provided?
• Did workers ignore clear training/rules?

Examples:

If a labourer falls through a fragile roof and there was no proper planning, no edge protection, no fragile roof controls, the employer and/or principal contractor are likely to carry most responsibility.

If a worker knowingly removes a guard and defeats a system they've been trained on, that may shift some blame, but investigators still ask why it was possible and what supervision existed.

Civil claims (compensation) usually go against the employer and their Employers' Liability insurance; criminal enforcement can hit the company, and in serious cases individual managers/directors.

6. EMPLOYERS' LIABILITY AND INSURANCE – WHAT IT MEANS FOR YOU

Under the Employers' Liability (Compulsory Insurance) rules, most employers must carry at least £5 million EL cover for claims by employees injured or made ill by their work.

That insurance pays compensation and legal costs when there's a valid claim – it does not remove their underlying legal duty to keep you safe.

If you're injured because your employer/contractor didn't meet their duties, any claim is normally against the company, paid via EL insurance, not against the individual worker who was hurt.

7. IN PRACTICE: THREE TYPICAL "WHO'S RESPONSIBLE" SCENARIOS

Scenario 1 – Fall from height from a scaffold Scaffold incomplete, no guardrails, no inspection tags. Worker falls and is seriously injured.

Likely responsibility focus:

• Employer and/or principal contractor for planning, safe system, scaffold competence, inspection.
• Scaffold company if they supplied and erected something non‑compliant.
• Worker's conduct only becomes central if they clearly misused a safe system in a way they'd been properly trained not to.

Scenario 2 – Struck by plant in a live yard No segregated walkways, poor traffic management, reversing vehicle hits a worker.

Responsibility focus:

• Employer/PC for traffic plans, segregation, banksmen, training and supervision.
• Possibly plant operator's employer.

Scenario 3 – Manual handling/back injury from repeated lifting Heavy materials routinely carried by hand, no trolleys or mechanical aids, no training.

Responsibility focus:

• Employer for failing to assess and control manual handling risks and provide aids/training.

In all of these, the starting point is: could the employer/PC reasonably have foreseen and controlled this?

8. WHERE THIS LEAVES YOU AS A WORKER OR SUPERVISOR

You are not expected to be a safety lawyer, but you're not powerless either.

You should expect:

• A proper induction and clear site rules.
• Suitable PPE, tools and equipment for the job.
• Clear method statements for high‑risk tasks (height, excavation, lifting, confined spaces).
• A chance to raise safety concerns without being punished – that's protected in law.

You must:

• Use equipment and PPE correctly, follow training and rules, and not deliberately put yourself or others at risk.
• Report defects, near misses and dangerous conditions as soon as you spot them.

If something serious goes wrong, the question is not "whose fault can we pin it on", but "who had the duty to stop this and didn't do enough?".

WHAT TO DO NEXT

• Know who the principal contractor and site manager are before you start any job.
• If you see something unsafe, report it to your supervisor and record it in writing.
• If something goes wrong, read S20a immediately - it covers what to do in the moment.
• Make sure you understand your own duties as a worker: use PPE, follow training, report hazards.
• If you are injured because of someone else's failure, speak to a union or solicitor early, not months later.

SOURCES

• Health and Safety at Work etc. Act 1974. https://www.legislation.gov.uk/ukpga/1974/37
• Construction (Design and Management) Regulations 2015. https://www.legislation.gov.uk/uksi/2015/51
• Management of Health and Safety at Work Regulations 1999. https://www.legislation.gov.uk/uksi/1999/3242
• Employers' Liability (Compulsory Insurance) Act 1969. https://www.legislation.gov.uk/ukpga/1969/57

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