Bathrooms are not electric-friendly. Steam, splashes, and standing water make one of the most hazardous rooms in the house when it comes to electrical safety.
That’s why regulations don’t leave much to chance. In the UK, the IET Wiring Regulations (BS 7671) lay down strict rules for what can and can’t be installed in a bathroom.
At the heart of these rules are “zones”, invisible boundaries around baths, showers, and sinks that dictate how close equipment can be to water.
Understanding these zones isn’t just for electricians; homeowners benefit too. Knowing why a heated mirror can’t be above the bath or why a pull cord is used instead of a switch inside the room helps avoid costly mistakes and keeps homes compliant.
This guide explains the zones set by BS 7671, safe distances, real life examples, and the pitfalls that catch people out time and time again.
The Principles Behind Bathroom Electrical Zones
The whole point of bathroom zones is about risk management. Electricity and water don’t mix, but not all of a bathroom is equal.
The closer to a water source, whether that’s a shower head or the inside of a bath, the higher the risk.
BS 7671 tackles this by dividing bathrooms into four main zones: Zone 0, Zone 1, Zone 2, and “Outside Zones”.
Each zone has its own requirements for Ingress Protection (IP) ratings, permitted equipment, and voltage restrictions.
A few key principles apply to all:
- Ingress Protection (IP ratings): The higher the risk of water, the higher the IP rating needed.
- RCD protection: All circuits supplying bathroom equipment must be protected by a 30mA Residual Current Device. This isn’t optional.
- Bonding: Metal pipework, baths, and showers must be earthed.
Without these measures, even a voltage kit can become lethal in the wrong conditions.
Zone 0 - Inside The Bath Or Shower Basin
Zone 0 is the worst. It’s the inside of a bathtub or the base of a shower tray, the place most likely to be fully submerged.
Only equipment that runs on 12V SELV (Separated Extra Low Voltage) or lower can be used here, and even then, it must be IPX7 (waterproof). Think purpose-built kit like underwater lighting or whirlpool pumps with sealed housings.
Standard light fittings, fans, or heaters have no place here. The rule is simple: if it can’t survive a dunk in water, it doesn’t belong.
Zone 1: Directly Above Bath Or Shower Up To 2.25m
Zone 1 goes vertically from the top of the bath or shower tray up to 2.25 metres. If there’s no tray, it starts from the floor where water sprays.
Here, the equipment needs to be IPX4 (splash-proof) or IPX5, where water jets are used. Typical fittings allowed in Zone 1 include:
- Electric showers.
- Sealed downlights for wet areas.
- Ventilation fans for bathrooms.
Anything running at 230V here must be RCD-protected. You’ll also notice there are no switches, controls have to be outside the room or operated by a pull cord.
Zone 2: 0.6m Beyond Zone 01
Zone 2 isn’t as tough, but it’s still part of the danger zone. It’s 0.6m beyond Zone 1, including above baths and showers.
Like Zone 1, the minimum requirement is IPX4. Examples here include:
- Towel warmers and heated rails (if earthed and RCD protected).
- Bathroom light fittings for splash zones.
- Shaver sockets with built-in isolation transformers.
Mistakes happen here when fittings with no IP rating are installed because they’re “outside the shower”. That 60cm buffer zone is there for a reason.
Outside Zones: The Rest Of The Bathroom
Beyond Zone 2 is the so-called “Outside Zone”. It’s less restrictive, but still bathroom-specific.
You won’t find standard 13A sockets here unless they’re more than 3m from a bath or shower. Even then, most installers won’t install them in bathrooms. The safer options are:
- Shaver units with isolation.
- Pull-cord light switches, or wall switches outside the bathroom.
- Heated mirrors and bathroom cabinets for damp conditions.
Underfloor heating is allowed, as long as the heating element is protected and the thermostat controls are outside the bathroom.
Common Electrical Equipment And Their Zone Ratings
It helps to look at real-world kit and where it fits:
- Electric showers: Zone 1 only, RCD-protected.
- Lighting: IPX7 in Zone 0, IPX4/IPX5 in Zone 1 or 2.
- Extractor fans: Zone 1 or 2, provided they’re splash-proof.
- Heated towel rails: Zone 2 or outside zones, properly earthed.
- Shaver sockets: Zone 2 or outside zones only.
- Washing machines: Generally not recommended in bathrooms; if unavoidable, only in outside zones with strict separation.
These rules keep installations consistent and predictable, something insurance companies and safety inspectors rely on.
Safe Distances And Practical Examples
Reading regulations is one thing; applying them in a real bathroom is another. Imagine a typical bath against a wall with a shower over it:
- The inside of the bath is Zone 0.
- From the top of the bath to 2.25m is Zone 1.
- Beyond that, 0.6m horizontally around the bath edge is Zone 2.
Ceiling height also matters. In bathrooms with sloped ceilings or shower cubicles, the zones may cut across walls at angles.
Small bathrooms are especially tricky; with everything close together, most of the space falls into Zone 1 or 2.
That’s why so many fittings are marketed as “bathroom-safe”, manufacturers design around these awkward layouts.
Common Pitfalls & Mistakes Homeowners Make
Plenty of DIY jobs fail on bathroom electrics. The biggest culprits include:
- Installing decorative lights not rated for bathrooms above baths.
- Putting standard extractor fans in Zone 1.
- Adding 13A sockets anywhere inside the room.
- Forgetting that all bathroom circuits require RCD protection.
- Hiring unqualified tradespeople who skip certification.
It’s worth remembering that even if a fitting “works”, it may not be compliant. Non-compliance can invalidate home insurance and put occupants at real risk.
Compliance, Certification, And Legal Responsibilities
In UK homes, bathroom electrics are not just a matter of best practice, they’re covered by Part P of the Building Regulations.
That means electrical work in a bathroom is classed as “notifiable” and must either be carried out by a registered electrician or signed off by building control.
Electricians issue an Electrical Installation Certificate (EIC) or a Minor Works Certificate, depending on the job.
These documents aren’t just paperwork; they’re evidence that the installation complies with BS 7671.
Skip this, and homeowners face more than safety risks. They risk voiding warranties, breaching building regs, and creating major problems when selling a property.
Useful Tools & Training For Electricians
Even seasoned electricians need to keep sharp on the nuances of bathroom zones. Updates to BS 7671 can subtly shift requirements, and mistakes are costly.
Digital resources and training tools are increasingly popular. Simulation apps like the Tradefox app give tradespeople a safe way to practise scenarios without risking live mistakes. These tools help reinforce understanding of safe zones, IP ratings, and correct equipment placement.
In an industry where regulations evolve, investing in refresher training pays off quickly.
Conclusion
Bathroom electrical zones might sound like technical jargon, but they boil down to one simple idea: keep electrics away from water, or protect them properly if you can’t.
By understanding Zones 0, 1, 2, and the outside areas, homeowners can make informed decisions, and electricians can deliver safe, compliant installations. With proper planning, the bathroom can be both practical and stylish without compromising safety.
In the end, electrics in wet rooms aren’t about cutting corners, they’re about building trust, one safe installation at a time.
