State officials also recently issued beefed-up safety protocols for work on construction job sites. The new rules require more frequent hand washing and cleaning job sites, while also requiring contractors to immediately send home workers with any signs of infection and work with local public health officials on extensive contact tracing.

“The Administration has followed federal guidance and tailored the essential business list to reflect the Commonwealth’s unique economy while maintaining strict guidelines for essential workers,” Sarah Finlaw, a spokeswoman for the governor, told Masslive.

But construction trade union leaders have been unimpressed. Arguing that the only way to keep workers and the public safe amid the pandemic is to keep them off jobsites, union officials have urged Baker to follow the lead of Boston Mayor Marty Walsh, who in March became the first leader of a major city in the United States to shut down almost all construction work, with mayors of neighboring Cambridge and Somerville taking similar action.

Pushing back, two of the region’s largest construction unions last week ordered members across Massachusetts to stay home and refuse to go to work at all but emergency projects, such as a new intensive care union in the city of New Bedford.

Thousands of members of the North Atlantic States Regional Council of Carpenters and of IUPAT District Council 35, which represents Boston-area painters, walked off their jobsites at the end of their shifts on April 6.

“We have had members who have been asking for this and who do not feel they are safe on job sites and don’t understand why construction workers are being sent to work while everyone else is staying home,” said Bert Durand, a spokesperson for the carpenters’ union.

In letters to their members, the business managers of both the carpenters’ and painters’ unions, who have more than 17,000 members across New England, said they had come to the conclusion that their members can’t work safely under current conditions.

“As the number of COVID-19 confirmed cases and deaths has dramatically increased, it has become apparent that working on construction sites in Massachusetts is abnormally dangerous,” wrote Thomas Flynn, executive secretary-treasurer of the carpenters’ union, in a letter to members.

The moves follow a call by the Massachusetts Building Trades Council, which represents 75,000 union members ranging from carpenters and painters to ironworkers and laborers, for a statewide construction moratorium until the end of April.

Meanwhile, workers from several other unions are helping deliver hospital beds for COVID-19 patients, including taking three days to convert the Boston Convention & Exhibition Center into a field hospital that opened on April 10. Crews, including members of the Sheet Metal Workers Local 17, Boston-based contractor Suffolk and the union carpentry team at New England Finish Systems, the union laborers at Select Demo Services, the Teamsters and union painters worked nonstop on the field hospital. 

"When our team at New England Finish Systems reviewed the site and the time constraints associated with constructing this facility it was decided that constructing the rooms off site would be the best way to insure the safety of all the men and women involved," said Lance Mazzariello, a union carpenter and field supervisor at New England Finish Systems. "Our union laborers and carpenters immediately went to work clearing the floor in our millwork shop, over the course of three nights over 90 union carpenters and laborers worked around the clock to build the panels comprised of over 10,000 sheets of drywall." 

The sheets were delivered on three trailers 24 hours a day, said Mazzariello, adding, "This project was a flawless example of the best in class union professionals working seamlessly across a multitude of trade disciplines."  

Half of the beds in the 1,000-bed hospital are reserved for members of the city’s homeless population who have tested positive for COVID-19 but don’t need full hospitalization.The makeshift hospital includes six acute care suites, 52 nurse stations, 48 bathroom facilities and a physical therapy suite.

“We will continue to help expand our healthcare capacity, so everyone can get the care they need,” Bob Butler, the Local 17s business manager, said in a statement.

Ray Martin, a project manager at Watertown-Mass.-based mechanical contractor, J.C. Cannistraro LLC, credited the sheet metal workers for the firm’s success on the project known as Boston Hope Medical Center. The firm added filtration and modifications to rooftop ventilation units to help adapt the convention center's air system for the temporary hospital. The sheet metal workers also helped prepare isolation rooms for COVID-19 patients at the convention center.

Martin said in a statement that the sheet metal workers “went above and beyond what’s expected of them. This isn’t part of their normal job. They did it for the people that are sick."

Touring another new 94-bed field hospital at the Joint Base Cape Cod on April 14, Baker announced two other field hospitals to help handle coronavirus cases. Baker said a 95-bed facility at UMass Lowell and 140 beds at UMass Dartmouth will come online soon.  

This story was updated with new information on April 16.