Flushing toilets connected to the mains water and drainage system where possible.
If main connection is not available, then facilities with a built in water supply and drainage tank
Portable chemical toilets can be used as last resort.
Toilets should be ventilated, lit and kept clean
There should be arrangements for cleaning the toilets (daily may not be sufficient) and an adequate supply of toilet paper etc
There should be wash basins with hot and cold (or warm) running water next to the toilets with soap and towels (or hand dryers)
The basins should be large enough to wash hands, face and forearms.
For more information for small sites see [Welfare facilities What you need to know as a busy builder ](http://www.hse.gov.uk/pubns/site4.pdf).