> Disclaimer: SiteKiln gives you plain-English information, not legal or health and safety advice. Always follow your site-specific risk assessments and talk to a qualified professional.
The short version
The Electricity at Work Regulations 1989 say anyone who controls electrical systems at work -- employer, self-employed, principal contractor -- must make sure they're designed, installed, maintained and used so far as reasonably practicable without danger.
On construction sites that usually means using 110 V centre-tapped-to-earth (CTE) kit for hand tools, planning and installing temporary supplies by competent electricians, and isolating or protecting existing electrics before you hack into a building.
What the law actually says (in plain English)
The Electricity at Work Regs apply to any electrical system at work -- permanent or temporary.
Key bits for you:
Reg 3 -- Dutyholders: if you're an employer or self-employed, you must comply with the regs for anything under your control.
Reg 4 -- Systems, work activities and protective equipment:
- Systems must be of such construction, and so maintained, as to prevent danger so far as reasonably practicable.
- Work on or near electrical systems must be carried out in a way that does not give rise to danger.
Other regs then cover things like protective measures, isolation, working dead/live, competence, and underground/overhead systems.
HSE's construction guidance then adds: refurbishment work must be planned, managed and monitored so people aren't exposed to live electrics, with "working dead" (proper isolation and proving dead) as the default when work could disturb or damage existing wiring.
Temporary supplies -- how they should be done
HSE's Electrical Safety on Construction Sites (HSG141) and guidance say a safe temporary site supply should:
- Be designed, installed and commissioned by competent electricians, not improvised from domestic sockets and leads.
- Use reduced voltage (usually 110 V CTE) for portable tools and site lighting in harsh environments, to cut shock risk.
- Have appropriate protection and distribution -- boards, breakers, RCDs, correct cable sizes, proper earthing and bonding.
- Be protected from damage -- cables routed safely, not through water, not crushed by traffic, sockets/enclosures suitable for wet, dirty, dusty conditions.
- Be inspected and tested before first use and at suitable intervals, with records kept.
User checks and inspections for portable tools and leads on construction sites typically follow HSE's pattern (for 110 V kit): daily/weekly user checks, monthly formal visual, and combined inspection and test at least every 3 months.
As the contractor/dutyholder, you are expected to make sure all that happens -- either through your own electricians or a competent firm.
110 V vs 230 V -- what's expected on site
HSE and industry guidance strongly favour 110 V CTE for portable tools on construction sites:
- 110 V centre-tapped gives a maximum of 55 V to earth, reducing risk of fatal shock in wet/damaged conditions compared to 230 V.
- It should be provided via appropriately rated transformers, with yellow plugs and sockets marking the reduced-voltage system.
- 230 V may still be used in some controlled situations (e.g. in dry, finished areas with RCD protection), but for rough construction areas, HSE expect 110 V or other reduced-voltage/SELV arrangements unless your risk assessment justifies otherwise.
Working near existing electrics
Refurb and fit-out is where a lot of people get hurt. HSE say those planning and managing the work must:
- Understand the building's electrical system -- via drawings, surveys, and liaison with the occupier or their electrician.
- Plan to work dead wherever possible -- isolating relevant circuits, locking off and proving dead before work that might damage cables, like chasing, drilling, cutting or strip-out.
- Use safe systems and competent people for any work on live systems -- this is specialist work, not for general operatives.
As a small builder, that means: don't let labourers "have a go" at electrics, don't chase blindly into walls where cables might be, and don't assume everything's dead just because a switch is off.
Your responsibilities and what to expect from others
If you're the main/only contractor, you're the electrical dutyholder on that job for anything under your control:
You're expected to:
- Use competent electricians for design, installation, alterations and testing of temporary supplies.
- Specify and enforce 110 V (or other reduced-voltage/SELV) for portable tools and site lighting where conditions warrant it.
- Make sure all kit is suitable for site conditions, protected from damage, and inspected/tested to sensible frequencies.
- Have clear rules about isolation and working near existing electrics -- especially on refurb work.
As a worker, you're expected to:
- Use the right voltage kit and RCDs provided, report damage, and not modify plugs/leads or bypass protections.
- Stop and escalate if you hit or expose cables, see obvious damage, or get shocks or tingles from equipment.
If you're being asked to run a site off domestic extension leads, use 230 V hand tools in standing water, or chase walls with no isolation or information on the wiring, that's not compliant with EAWR or HSE's construction guidance.
Quick check: are the electrics safe on this site?
On any UK site, ask yourself:
Voltage: Are portable tools and site lighting in rough, wet or exposed construction areas running at 110 V centre-tapped to earth (yellow plugs/transformers), not straight 230 V?
Protection: Are all temporary boards and 230 V circuits that are in use protected by appropriate breakers and RCDs, and are transformers/boards in good condition and suitable for outdoor/site use?
Cables and kit: Are leads routed to avoid damage (no crushing, trip hazards, water, sharp edges), with no taped-up joints, exposed cores, broken plugs or DIY modifications?
Isolation and info: Before drilling/chasing/stripping, do you know where existing cables are, and are relevant circuits properly isolated and proved dead rather than just "we think it's off"?
If any of those are a clear "no", the electrics on that site are not being managed to UK HSE expectations under the Electricity at Work Regs.
What to do next
- Check that all portable tools on your current job are running at 110 V (yellow plugs) in rough/wet areas, not 230 V.
- Look at your leads and plugs today -- any taped joints, exposed cores or broken plugs need replacing now, not next week.
- Before drilling or chasing on your next refurb job, make sure you know where the existing cables are and that circuits are isolated and proved dead.
- Make sure your temporary supply was designed and installed by a competent electrician, not improvised from domestic extension leads.
- Book PAT testing for your tools if it's overdue -- the intervals for construction kit are tighter than for office work.
Sources
- Electricity at Work Regulations 1989 -- duties on employers/self-employed to ensure electrical systems are safe.
- Health and Safety at Work etc. Act 1974 -- general duties.
- Construction (Design and Management) Regulations 2015 -- planning and management duties.
- HSE -- Electrical safety on construction sites (HSG141) and systems in buildings guidance.
Disclaimer
This guide is general information for small UK construction businesses and trades, not formal legal or electrical engineering advice.
SiteKiln is not a law firm and this page is not a substitute for getting advice on your specific situation.
Health and safety law and HSE guidance on electrical safety are updated from time to time, and how the Electricity at Work Regulations apply will always depend on the exact facts on your job and your role.
If you're dealing with a serious electrical safety issue, shock incident, or complex temporary supply, get specific advice from a competent electrician and/or solicitor before you make big decisions.
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