Negotiations between the Service Union United PAM and the Property Management Association, which represents the employers, broke down last week. Following that, PAM issued a strike warning and an overtime ban.
If no deal is reached Tuesday, the union will launch a two-day strike next Wednesday that will involve 25,000 employees, mostly cleaners and real estate managers.
Nearly 50,000 employees are covered by the collective deal on pay and conditions in the facilities services sector.