BS 7671 treats rooms with a bath or shower as special locations. Section 701 divides the space into zones based on how likely equipment is to get wet, and sets what can go in each one.
The zones
| Zone | Where | What it means |
|---|---|---|
| Zone 0 | Inside the bath or shower tray | Only equipment made for it, at least IPX7, and separated extra low voltage of no more than 12V AC |
| Zone 1 | Directly above the bath or tray, up to 2.25m from the floor | At least IPX4. IPX5 where jets of water may be used for cleaning |
| Zone 2 | The 0.6m band beyond zone 1, up to 2.25m | At least IPX4. IPX5 where jets of water may be used for cleaning |
| Outside the zones | The rest of the room | No zone IP rating, but the room's other rules still apply |
Sockets and shaver points
Standard 13A sockets are not allowed within 3m horizontally of the boundary of zone 1. That rules them out of most hotel and HMO bathrooms. A shaver supply unit made to BS EN 61558-2-5, such as the BG 940, is the exception: it can be installed in zone 2 where it is unlikely to be hit directly by shower spray.
RCD protection
Every circuit serving the location needs 30mA RCD protection, including lighting and the shower circuit. This is a common gap when an older room is only partly rewired.
Switches
Keep light switches outside the zones, or use a ceiling pull cord. Inside zones 1 and 2 only switches that are part of a SELV circuit are allowed.
This note is a summary for planning and ordering. Design and certification of the installation remain with the qualified electrician responsible for the work.