"Workday" is a day when you usually work. "Saturday is a workday at my restaurant, but Monday is a day off." "Workaday" = mundane, not extraordinary, unremarkable. "My holiday in Thailand was a welcome break from my workaday life." "I experience the same workaday hassles as everyone else: driving in traffic, shopping for necessities, doing laundry...."

"workaday" does not exist.