The immersive yet understated conversion of a military pier into an art school at Fort Mason, completed this fall, will only gain character as students make it their own. But it already shows why the design firm involved, Leddy Maytum Stacy, is the architecture profession’s firm of the year.

The project involves the historic preservation of a 1912 structure, yet the clarity of the transformation embodies the firm’s clean modernism. Solar panels on the long, pitched roof bear witness to Leddy Maytum’s emphasis on sustainable design. And the new Fort Mason campus of the San Francisco Art Institute has an unmistakable public, social presence — an aspiration that has defined the South of Market firm from the start.

“We started out with a preference not to be fashionable for fashion’s sake,” said Richard Stacy, who founded the firm in 2001 with Marsha Maytum and William Leddy. “There are more substantial issues to be addressed.”

The tallest of the three’s completed projects is only nine stories, well below skyline scale. They’re often embedded in urban settings, such as Oakland’s Merritt Crossing with its 70 low-income senior apartments along Interstate 880.

Affordable housing is a specialty, with eight complexes in San Francisco now under construction or in the works. Private schools, including a planned expansion of Nueva Middle School in Hillsborough, double as laboratories in how to create “carbon-neutral” complexes where no more energy is consumed than what is produced on-site over the course of a year. The firm has explored the concept of “universal design,” where buildings can be navigated intuitively even when a user has disabilities, dating back to 2010’s Ed Roberts Campus in Berkeley.

“What we’re excited about is the way that architecture can be a catalyst for change beyond property lines,” Leddy said.

These cultural threads were emphasized when the American Institute of Architects presented Leddy Maytum Stacy with the 2017 Architecture Firm Award. The work “makes a compelling case for the power of design to improve the lives of everyone,” reads the citation, as well as “a liberating sense of empowerment to the communities they serve.”

The firm now has 28 employees, its highest count ever, in a small but atmospheric South of Market building with thick brick walls and a high timber ceiling.

The firm’s two most recent completed buildings are in San Francisco. Both involve historic preservation. Each is one-of-a-kind.

Most visible is the firm’s snug new home for the Commonwealth Club, founded in 1903 and host to hundreds of lectures each year. It fills a site from the Embarcadero to Steuart Street just south of Mission Street, next to Boulevard Restaurant.

The function of the building is straightforward, to provide the club with meeting rooms and a 300-seat auditorium, but the site’s legacy is not. It held a three-story, much-altered 1910 building that between 1932 and 1934 held the union hall for the International Longshoremen’s Association.

Outside on Steuart Street is where two longshoremen were shot and killed by police during a waterfront strike on July 5, 1934, and where the funeral procession for the victims began four days later.

The new building retains the Steuart Street facade, which now features a historic plaque, and pulls the upper floor of the three-story structure back from the original. The side facing the Embarcadero is all new, in glass that’s a design gesture to the club’s public mission.

It’s an earnest fit but an awkward one, though the spaces inside will serve their purpose well.

At the Fort Mason pier that now houses the art institute’s graduate studios, by contrast, the confident restoration is a triumph.

The stocky exterior of the Spanish-flavored shed has been patched, cleaned and repainted a creamy white. Step inside and you’re soon aware of two things — the lean but muscular depth of the tall space, and the monochromatic but genuinely fitting insertion of two floors for students within a shell used as a supply warehouse during World War II, when Fort Mason was a major embarcation point for soldiers heading to the Pacific theater.

The aged frame sets the tone for the interior, with its procession of steel trusses that support the wooden roof slit by a narrow rise in the middle, light streaming down from small windows on both sides.

The art institute’s studios slide below this, leaving open views of the industrial trusses. Architectural additions are open as well, and chosen with care; the railings of the mezzanine catwalks are thin metal rods, like some elegant roll-down screen.

The old pier is part of the Golden Gate National Recreation Area and the Fort Mason Historic District. These factors mean layers of extra scrutiny — but Leddy Maytum has a track record of creative restoration, including three buildings in the Presidio, and it knows how to persevere with regulators for the greater good.

Sometimes this means subtraction, as when the firm persuaded federal planners to replace a single row of opaque glass panes above the entrance with clear ones, so that the offices inside would have a sliver of a view. There also are additions: The rooftop solar panels should satisfy 85 percent of the pier’s energy needs.

More important for the mission of the art school — which retains its Chestnut Street campus on the east slope of Russian Hill — the space within is ideal for students. Individual artist studios are clustered along the ground floor nave and mezzanine catwalks, 150-square-foot spaces clustered in culs-de-sac of six.

“It’s a honeycomb, but you can come out and feel like part of something whole,” Maytum said. “We’re always trying to make each design solution solve several problems at once.”

The only aspect of the reborn pier that feels off is ... things feel a little too clean. The walls need a few scuffs, stray splotches of paint or slapdash but spirited student posters.

They’ll come. In the meantime, Leddy Maytum Stacy likely will continue to thread more buildings through the landscape, new and restored, of lasting value for us all.

Place is a weekly column by John King, The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron