What a day porter is actually for
A porter exists to hold a standard during occupied hours. The work is short-cycle and repetitive: checking and servicing washrooms, resetting waiting and breakout areas, clearing waste before it overflows, wiping high-contact surfaces and dealing with spills as they happen. It is not a shortened version of the evening clean and it should not be scoped as one.
The value is greatest where the condition of a space at two in the afternoon matters to somebody. Reception areas, waiting rooms, public washrooms and busy kitchens all fall into that category. Where the only people who see the space are the staff who work in it, the case is much weaker and the money is usually better spent on the evening attendance.
