Laytime & demurrage
Once on demurrage, always on demurrage
Meaning
Once on demurrage, always on demurrage means that after laytime expires, laytime exceptions stop applying and demurrage runs continuously.
Once on demurrage, always on demurrage explained
Exceptions such as weekends or weather only protect the charterer while laytime is running. Once the ship is on demurrage, those exceptions no longer interrupt the clock unless the charter clearly says they apply to demurrage too.
The principle is a default rule, and well-drafted charters often list specific events that do interrupt demurrage, such as delays caused by the ship.