The relevant legislation is the Workplace (Health, Safety and Welfare) Regulations 1992. Regulation 20, Sanitary conveniences, states:
The Approved code of practice goes on to give minimum numbers of facilities:
(The number of people at work shown in column 1 refers to the maximum number likely to be in the workplace at any one time)
Number of toilets and washbasins for mixed use (or women only):
|Number of people at work||Number of toilets||Number of washbasins|
Toilets used by men only:
|Number of men at work||Number of toilets||Number of urinals|
L24, Workplace health, safety and welfare, approved code of practice and guidance, (ISBN 0717604136 - available from HSE Books).