The job duties of a janitorial subcontractor involve performing cleaning and maintenance services on a contract basis. As a subcontractor, a general contractor hires you to work as a janitor in a building, facility, or with different clients in different facilities. You may work on a one-time cleaning project or subcontract on an ongoing basis. Your responsibilities may vary depending on the nature of each contract. You may vacuum floors, clean bathrooms, and change lights as necessary. As a subcontractor, you may perform one specific task while other subcontractors handle different janitorial duties.