The Heritage Foundation’s renovation of 208 Massachusetts Ave. NE is nearly complete, and the think tank expects to begin occupying the former apartment building this May.

Heritage acquired the adjacent structure almost two years ago, nearly doubling the space of its facility at 214 Massachusetts Ave. NE.

Once completed, the renovated structure will offer a 230-seat auditorium, new conference rooms and four floors of intern housing — totaling more than 60,000 square feet.

The foundation already has interns scheduled to arrive in late May. About 55 to 60 students intern at Heritage every summer. The dorm facility will make it easier for the students to work for Heritage, as finding housing is one of the biggest challenges of interning in Washington, according to Heritage Executive Vice President Phil Truluck, who is overseeing the project. During the rest of the year, when the foundation has fewer interns, it will share the dorm space with other organizations that need intern housing.

Eventually, the think tank plans to renovate the middle part of the building for additional office space, but for now that section will remain unfinished.

“There are some parts we aren’t renovating [right now] because we don’t need the space,” Truluck said.

In addition to the new interior, the building will also boast a roof deck, which Heritage plans to use for receptions and other events. “It’s going to be neat,” Truluck said. “We had to replace the roof anyway.”

The $9 million project was scheduled to be completed last fall, but construction started late due to difficulties acquiring the necessary permits from the District.

“We had hoped to start it last January, but we lost time in the permitting process,” Truluck said. The construction got under way last March, and the 13-month project will be completed by early May.

The building — which once housed about 100 tenants, a dry cleaner and Neil’s Outrageous Liquor, Wines & Deli, a mainstay for Senate staffers — was a gift from the family of the late Thomas Johnson.

A former contributor to Heritage, Johnson was best known for his part ownership in the Pittsburgh Pirates baseball team. The gift was valued at $8.5 million.

A second gift of $2 million, by Heritage Foundation trustee Douglas Allison and his wife, Sarah, made the auditorium possible.