The following information is a guide to help you understand what fittings can be placed where. This is not an installation guide and reference should be made to the IEE Wirings Regulations or a qualified electrician.
Firstly it is important to understand the rating by which bathroom and some outdoor lights are classified. IP rating stands for ‘Ingress Protection’ and is always followed by two characters. The first character specifies the degree of protection against particles or solid objects. Starting with 0 for no protection it runs up to a maximum of 6 which is total protection against ingress of dust. Of more interest here is the second digit that states the degree of protection from ingress of moisture. This ranges from 0 for no protection to 8 for a light which may be totally submerged in water up to a specified depth.
The ratings that interest us are IPx4 (x is used in this case because there is no requirement in the regulations for a level of dust protection). Lights sold as IPx4 will have been tested for protection against water splashing from any direction.
The diagrams above shows a bathroom split into four clear zones. In zones 1, 2 and 3, if there is likelihood of a water jet being used for cleaning purposes a minimum of IPx5 is required.
Zone 0 is inside the bath or shower itself and any fittings used here must be low voltage (max 12v) and be rated IPx7 which is total protection when immersed in water.
Zone 1 is above the bath to a height of 2.25m. A minimum rating of IPx4 is required here.
Zone 2 is an area stretching to 0.6m outside the bath and above the bath if over 2.25m. An IP rating of at least IPx4 is required here.
Zone 3 is anywhere outside zones 0, 1 and 2 (subject to specific limits) and where no water jet is likely to be used there is no IP rating required.
The IEE Regulations do not make specific reference to wash basins but in the opinion of The Lighting Association they should be treated as Zone 2 (i.e. IPx4)