Gov. Charlie Baker on Monday announced plans for Phase 1 of his four-phase approach to reopening the state.

As they reopen — or remain open — businesses are required to follow mandatory workplace safety standards and sector-specific safety protocols and best practices.

In addition to all businesses deemed essential by previous orders, construction and places of worship are among those included in Phase 1, with reopenings on May 25. Barber shops and hair salons also are included in Phase 1. Office space may open to 25 percent capacity, except in Boston.

Personal services such as nail salons, day spas, massage therapy, tattoo parlors and electrolysis studios are in Phase 2. Also in Phase 2 is the reopening of restaurant dining areas (with restrictions).

The phases will be a minimum of three weeks apart, possibly longer if there are concerns about the virus spreading.

Gyms and fitness studios are in Phase 3, as are bars, museums movie theaters and performance venues (concert halls and theaters).

Phase 4 includes large venues, including arenas, stadiums and nightclubs.

Some youth sports activities will be included in Phase 2, along with recreational day camps. Residential summer camps are in Phase 3.

“This is something no one’s ever done before — shutter then reopen everything from a beachfront to a factory floor with standards in place to slow the spread of a highly contagious virus,” Baker said. “So I ask everyone to keep this mind: This guidance asks people to change behaviors. And it changes the way some of our favorite places look and feel. This is not permanent. At some point there will be treatments, and ultimately a vaccine. But for the foreseeable future, everyone needs to continue to do the right things to bring the fight to the virus so that we can continue to move forward.

“Today the Department of Health also updated the stay at home advisory to reflect this stage of the reopening process. The new safer at home advisory instructs everyone to stay home unless they’re headed to a newly opened facility or activity. And it also advises those over the age of 65 and those with underlying health conditions to stay home except for absolutely necessary trips to things like health care and groceries.

“This new advisory is important. As we enter this phased reopening, it’s important to remember that everyone is safer at home. The virus will be with us throughout the reopening process. And everyone’s required to cover their nose and mouth if you can’t maintain 6 feet of distance from those around you. Everyone has a responsibility to wash their hands, distance themselves from others, and be vigilant about symptoms so that you can stay home and you should stay home if you feel sick. How well everyone does these things will determine how well we move into later phases.”