Bathroom electrics in the UK are governed by the wiring regulations, BS 7671, which divide the room into zones around the bath and shower. Zone 0 is inside the bath or shower tray and needs equipment rated at least IPX7. Zone 1 is the space directly above it, and zone 2 is a band around zone 1; both need equipment rated at least IPX4. Every circuit serving the bathroom needs RCD protection, and most electrical work in a bathroom is notifiable under Part P of the Building Regulations, so it should be designed and installed by a registered electrician. Ventilation is covered separately by Approved Document F, which sets minimum extract rates for bathrooms. What follows is a homeowner’s outline to help you plan the room; it is not a substitute for a qualified electrician’s design.
Bathroom electrical zones 0, 1 and 2
The zones are measured from the bath or shower, not from the walls of the room, so their position changes with the layout. That is why the electrical design has to follow the bathroom design rather than precede it.
Zone 0
The interior of the bath or shower tray. Only equipment designed to be immersed may be installed here, at extra-low voltage, and it must be rated at least IPX7. In a domestic bathroom very little goes in zone 0 apart from lighting made for the purpose.
Zone 1
The space directly above the bath or shower tray, up to a set height above the floor. Equipment here must be rated at least IPX4, and the regulations restrict what may be fitted. Shower pumps, electric showers, extractor fans and some lighting can be installed in zone 1 if they are suitable for the location. Downlights over a bath or shower are usually chosen with this zone in mind.
Zone 2
A band extending outwards from the edge of zone 1, where splashing is likely. Equipment here also needs at least IPX4, and a higher rating where water jets are used for cleaning, as in some commercial settings. Mirrors with lighting, wall lights near the bath and shaver supply units commonly fall in or close to zone 2.
Outside the zones, the regulations still apply. Ordinary socket outlets are only allowed in a bathroom if they are a set distance from zone 1, which in most domestic bathrooms rules them out. Shaver supply units made to the relevant standard are the usual way to provide power for shavers and toothbrushes.
IP ratings in plain terms
An IP rating describes how well a piece of equipment keeps out solids and water. The second digit refers to water. IPX4 means protected against splashing from any direction. IPX5 adds protection against water jets. IPX7 means protected against temporary immersion. The X simply means the dust rating has not been specified. When you choose a light fitting, mirror, fan or towel rail, check the IP rating on its specification sheet and give it to your electrician with your layout drawing, so they can confirm it suits the zone where it will be fitted.
RCD protection and Part P
All circuits supplying a room containing a bath or shower must be protected by a residual current device, which cuts the supply quickly if current leaks to earth. In older houses this often means altering or replacing the consumer unit as part of a bathroom refurbishment, which should be allowed for in the budget and the programme.
Part P of the Building Regulations in England covers electrical safety in dwellings. Installing a new circuit, replacing a consumer unit, or adding to or altering circuits within the special location around a bath or shower is notifiable work. The simplest route is to use an electrician registered with a competent person scheme, who can certify the work and notify building control on your behalf. You should receive an electrical installation certificate and a building regulations compliance certificate when the job is finished. Keep both with the house documents; buyers’ solicitors ask for them. Rules in Wales, Scotland and Northern Ireland differ, so check locally.
LED mirrors and heated towel rails
An illuminated mirror needs a fixed supply, usually through a fused spur outside the bathroom or a switched connection unit placed where the regulations permit, and its IP rating must suit the zone. Decide on the mirror before first-fix, because the cable has to come out of the wall at the right height and position behind it. A mirror with a demister pad, or a mirrored cabinet with lighting and a built-in shaver socket, needs the same planning.
Heated towel rails come in three types: plumbed into the central heating, electric only, or dual fuel with an electric element so the rail can run when the heating is off. Electric and dual-fuel rails need a fixed connection, normally through a fused spur whose switch is placed where the regulations allow, often outside the room, and the element must be suitable for the zone where the rail sits. A timer or thermostatic control on the spur makes an electric rail far cheaper to run. Plumbed rails need flow and return pipes positioned at first-fix to suit the rail’s centres.
Extractor fans and Approved Document F
Approved Document F sets minimum extract rates for bathrooms in new work and in many refurbishments, either for intermittent extraction while the room is in use or for continuous running at a lower rate. Your electrician or ventilation installer should size the fan to meet the current requirement for the room and its use. In practice a fan that meets the minimum on paper can fall short if it is installed badly.
Three details make the difference. Duct runs should be as short and straight as possible, discharge to outside rather than into a roof space, and use rigid ducting where it can be fitted. The room needs a route for replacement air, usually a gap under the door, so the fan is not working against a sealed room. And the fan should run on after the light is switched off, or be controlled by a humidity sensor, so the room clears properly. A fan positioned in zone 1, over a bath or shower, must be suitable for that zone and is often an extra-low-voltage unit with a remote transformer.
Poor extraction shows up on painted joinery, timber vanity units and ceilings long before anywhere else. If the room will have furniture from our joinery workshop or bathroom furniture in painted timber, settle the fan position and ducting route on the drawing before the ceiling goes up.
Planning the electrics with the bathroom layout
The order matters: fix the bath, shower and basin positions first, then the electrician can draw the zones and place lights, mirror supply, towel rail spur, fan and switches around them. Our design service produces a layout drawing and an item schedule that your electrician can work from. Give them the drawing, the specification sheets for every electrical item, and the ceiling height before first-fix, and ask them to mark the switch and spur positions on the drawing so nothing ends up behind a mirror or a cabinet.