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 contact can lower body resistance and make electric shock more severe. BS 7671 sets zones around baths and showers to guide equipment selection and water protection. Assess the actual electrical supply and metalwork; neither a dry-looking floor nor a nearby pipe establishes 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. A mains-powered fitting is not permitted merely because it is watertight.
Above a bath or basin, 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 basin, 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 basin, Zone 2 adds a 0.6 m band beyond Zone 1 with the same upper limit. A shower without a basin 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.
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.