About 200 janitors who clean Tufts University unanimously voted Thursday to authorize a strike if a new contract agreement isn’t reached with the school’s maintenance contractor by Oct. 31.

The janitors work for Newton-based C&W Services, a building services provider for commercial and industrial properties. They are demanding cost of living wage increases, opportunities for more full-time jobs, and maintaining affordable health care benefits, according to 32BJ of the Service Employees International Union, which represents the workers.

“We don’t take a strike vote lightly, but the hard-working men and women who take care of Tufts are ready to do what’s necessary to support their families,’’ Roxana Rivera, vice president of 32BJ SEIU, said in a statement. “Too many people at Tufts still have to cobble together two, three jobs just to pay the bills. We can avoid this problem by promoting full-time work and get a good contract.’’

C&W Services, a division of brokerage firm Cushman & Wakefield, did not comment directly on the vote but reiterated in a statement Thursday that it’s offered the union a wage increase, health benefits with no contributions from the workers, increases to pension and training funds, and contributions to a legal services fund.

Tufts is not involved in the negotiations but said in a statement that it remains hopeful the two groups will reach an agreement. The school added it has a contingency plan in place if a strike cannot be averted.

“The plan would prioritize student and healthcare spaces on all of Tufts’ campuses, such as dining facilities, dorms, bathrooms, locker rooms, clinics, and animal hospital facilities,’’ said spokesman Patrick Collins.

Bargaining sessions, which have been ongoing since August, are scheduled to continue Friday and Monday, according to the union. The custodians’ current three-year contract expires Monday. If an agreement isn’t reached by then, the janitors could walk off the job.

About 60 percent of the janitors who maintain the campus, which straddles Somerville and Medford, work full-time, according to 32BJ SEIU. Currently the janitors, a mostly immigrant workforce, get an hourly wage of $19.35. The union declined to say how much more it is requesting.

The vote comes one day after about 750 dining hall workers at Harvard University approved a new five-year contract with the school, ending a three-week strike. 32BJ SEIU also reached an 11th-hour deal last month for about 13,000 janitors who clean thousands of office buildings in the Boston area that resulted in a 12 percent pay increase over four years. And in June the union negotiated a contract for Massachusetts Institute of Technology janitors that will increase their hourly wages to $23.67 over three years.

Katheleen Conti can be reached at kconti@globe.com. Follow her on Twitter @GlobeKConti.