Identify the busiest ordinary period
For work, include overlapping trades and breaks; for a gathering, include helpers as well as guests. Explain the hours of use and which existing bathrooms remain available. Describe separated parts of the property that may need their own convenient provision.
Ask what the recommendation assumes
Quantity, washing, accessible options and cleaning need to be discussed together. If use changes, ask whether the original arrangement remains suitable. A planning suggestion should not be treated as a universal regulatory ratio or confirmation that the whole site meets applicable requirements.
Prepare separate work and gathering briefs
For building work, record the largest overlapping crew, shift hours, working days and bathrooms available to those workers. For gatherings, record simultaneous attendance, duration, helpers, food or drink service and when permanent facilities can be used. These are different patterns of demand.
Take those assumptions into the equipment discussion together with washing, accessible provision and planned service. Ask for the basis of the recommendation and revise it when the underlying plan changes. This page does not supply an unsupported calculator result, legal minimum or guaranteed waiting time.