Boston Public Schools planning and engineering professionals have reached a new labor agreement with the city after several years of stalled negotiations.

The sticking point, said chapter chair Bob Ridlon, was that the school department insisted on getting contract language that would allow it to bring in volunteers to do some of the members’ work. “We feel that would be pushing the department in the wrong direction,” said Ridlon.

The Department of Planning and Engineering, with about 35 Local 888 members, oversees school construction work. Members have licenses in such areas as plumbing, pipefitting and electrical and building systems.

The upshot of negotiations is both a one-year contract running into 2020 along with a 3-year contract that started Sept. 1, 2016. This involves fully retroactive pay.

Across-the-board wage increases for all positions came in at: 2 percent annually kicking in with July 2016, 2017, 2018 and 2019.

Negotiations for a new Professional Employees Chapter contract are expected to begin soon.