Why bath and shower rooms are split into zones, the IP rating each needs, and when work there becomes notifiable.
Why bathrooms are split into zones
Wet skin lowers the body's resistance and makes an electric shock more severe. BS 7671 sets zones around baths and showers that decide what equipment can go where and how well it must resist water. Assess the actual electrical supply and metalwork: a dry-looking floor or a nearby pipe tells you nothing about electrical safety.
Zone 0, 1 and 2
With a bath or shower tray, Zone 0 is the space inside it. Without a tray, this zone instead covers the shower floor up to 0.10 m high, over the same horizontal area as Zone 1. Equipment in Zone 0 must be suitable for the location, fixed and permanently connected, with at least IPX7 protection and a SELV supply limited to 12 V AC or 30 V ripple-free DC. The safety source is outside all three zones. Being watertight does not make a mains-powered fitting allowed there.
Above a bath or shower tray, Zone 1 reaches 2.25 m above the finished floor, or the highest fixed shower head or water outlet if higher. For a shower without a tray, measure 1.2 m horizontally from the fixed outlet on the wall or ceiling. Zone 1 equipment needs at least IPX4 against splashing, or IPX5 where jets are expected. Its type and installation must also be permitted in that zone.
Beside a bath or shower tray, Zone 2 adds a 0.6 m band beyond Zone 1 with the same upper limit. A shower without a tray has no Zone 2. Equipment ordinarily needs at least IPX4, with IPX5 for jets. A compliant isolated shaver supply unit has a specific exception in Zone 2 when direct spray is unlikely; an ordinary mains socket does not qualify. Ordinary sockets need 2.5 m horizontal clearance from Zone 1.
An ordinary washbasin does not create these bath/shower zones. Its splash exposure still matters when selecting nearby electrical equipment.
Walls, doors and fixed partitions can affect the extent of a zone where they effectively limit it. Assess that layout before deciding whether equipment in a cupboard is inside a zone. Check the appliance instructions, IP rating and access for servicing and safe isolation. The circuit requirements for the room still apply.
RCD protection and notification
Provide 30 mA RCD additional protection for low-voltage circuits serving the room and for low-voltage circuits passing through Zones 1 or 2. The device cannot replace required earthing, insulation or equipment suitability, and a working RCD does not make live work safe.
For Part P in England, notification depends on the type and position of the work. A new circuit is notifiable wherever installed. An addition or alteration to an existing circuit is notifiable within the defined special location: 0.6 m beyond a bath or tray, or 1.2 m from the attached shower head without a tray, up to 2.25 m or a higher wall- or ceiling-mounted shower head. Rooms containing swimming pools or sauna heaters also count. Like-for-like repair or replacement is different; all work still needs the appropriate inspection, testing and certification.
Switches and appliances in the room
A 230 V plate switch must sit outside the zones, at least 0.6 m from the edge of the bath or shower tray; in zone 2 only switches on SELV circuits and shaver supply units are allowed. The insulating cord of a cord-operated switch may hang within zones 1 and 2, which is why ceiling pull-cord switches are the usual choice inside a bathroom, including as the double-pole isolator for an electric shower. A splash-proof cover does not let a mains switch into the zones. A washing machine or tumble dryer may go in a room with a bath or shower only where its manufacturer allows it, supplied from a switched fused flex outlet outside the zones and protected by a 30 mA RCD.
Reading an IP code
An IP code has two figures. The first, from 0 to 6, grades protection against solid objects and dust: 4 keeps out objects larger than 1 mm, 5 is dust-protected and 6 is dust-tight. The second, from 0 to 9, grades protection against water: 4 is splashing from any direction, 5 is jets and 7 is immersion for up to 30 minutes between 15 cm and 1 m deep. The jets are low-pressure at 5 and powerful at 6. Read each figure by its place: in IP54 the 5 is the dust figure, dust-protected, and the 4 the water figure, splashing. An X stands in for a figure that has not been rated, so IPX4 gives a water rating of 4 and no rating for solids.