The head of the state’s largest building trades union has cleared its 13,000 members to return to job sites statewide starting today after a 15-day work stoppage fueled by concerns over COVID-19.

The North Atlantic States Regional Council of Carpenters directed its members to stop working on construction sites starting April 6 based on fears many construction projects did not have adequate protections in place to prevent the spread of the disease.

In a letter issued Sunday, April 19, the union Executive Secretary-Treasurer Joseph Byrne said the union had held negotiations with contractors statewide about improving site safety. Demands included training workers in COVID-19 safety protocols, screening workers for symptoms daily, creating new construction techniques that incorporated social distancing, providing personal protective equipment and improving hygiene at job sites.

“Though there are still concerns about COVID-19 in Massachusetts, the union believes that our contractors and members are committed to creating and maintaining a safe work environment,” Byrne wrote.

Union members are now allowed – but not directed – to return to construction projects for health care facilities, public works, infrastructure, schools, housing, roads and bridges. The union said it would monitor contractor compliance with safety measures.

The smaller, 4,000-member International Union of Painters and Allied Trades District Council #35 called a similar work stoppage at the same time, but since then have been working with contractors on a case-by-case basis to negotiate safety plans for individual job sites.

The two strikes came after a tussle between Gov. Charlie Baker and Boston Mayor Marty Walsh over local construction bans. Gov. Charlie Baker has allowed certain categories of construction to continue statewide even as cities such as Boston and Cambridge ordered most projects to come to a halt.

Boston’s freeze on city-permitted construction continues, but Walsh issued new site safety guidance Friday for work on infrastructure and utility projects, health care projects and residential remodeling or the construction on residential buildings of three units or less. The city says all projects must implement the policy by April 27.