The large panel of wood that hovered in the air above a De Haro Street construction site last Friday was something never seen before in the city.

It’s formed from seven layers of black spruce grown in Quebec, 24 feet long and 8 feet wide, each layer glued one-to-the-next and then pressed together like a panini. A crane slowly lowered it into place atop thick wooden columns and beams — the first of hundreds of panels that will be an integral part of the structural frame of a four-story, 60-foot-high commercial building.

“Basically, it’s a very sophisticated Lincoln Logs set,” said John Fisher, project manager for SKS Partners, 1 De Haro’s developer. “That’s how we explained it to our investors.”

Touted by boosters as an eco-friendly alternative to concrete and steel, with a tactile warmth that theoretically makes for a more nurturing workplace, large buildings of structural timber have developed a cult following in other regions. California, however, only added mass timber to the state’s building code in 2016.

The newcomer at 1 De Haro, designed by Peter Pfau of Perkins and Will, will be the first mass timber project in San Francisco, but two more are close behind. And whatever the environmental impact, their arrival should add a twist to the too-predictable look of so many new Bay Area buildings.

One will be a five-minute walk away on Hooper Street: California College of the Arts plans to break ground next spring on a trio of pavilions made of laminated timber that will rise from a shared concrete base. The other will be wood from bottom to top, a six-story structure at Pier 70. The design is as tall as California allows and should be the nation’s largest timber office building when it opens in 2022.

“We wanted people to walk into the lobby and feel the wood right away,” said Cutter MacLeod, the project manager at Brookfield Properties, which is redeveloping Pier 70 as a mix of housing, offices and shoreline public space.

It will be among the first buildings constructed at Pier 70, a former shipyard. It’s also the first mass timber structure by Brookfield, which is active across the country.

As is the case with 1 De Haro, there’s a cost premium involved in using wood rather than steel or concrete. But both developers say the approach of having large sections fabricated off-site shortens the construction process by several months, which helps bring down costs.

There’s also the novelty of being an early user of a renewable resource that, when harvested properly, has a smaller carbon footprint than traditional commercial buildings.

“The premium is more than worth it,” MacLeod said. “It’s a way to push innovation, and it also gives the neighborhood a building designed to be the first of its kind.”

The most visually striking of the projects will be the one at California College of the Arts. Designed by Studio Gang, each pavilion will have outdoor walkways within diagonal seismic braces made of wood as well. The 11-foot-deep walkways also shade the classrooms from direct sunlight, helping to trim energy demands.

“The design is rooted in the desire to be carbon neutral and net-zero,” said Steve Wiesenthal, who heads Studio Gang’s San Francisco office. The carbon embedded in the panels, beams and braces is part of the strategy. “Timber seemed to be the way to go, and we didn’t want to hide it.”

That’s what happens in standard wood buildings, such as any new suburban house framed in 2-by-4s. Those structures, though, are then encased in fireproofing — a necessary defense given wood’s flammability.

Asked if the combination of wood plus glue isn’t asking for trouble, structural timber boosters emphasize the thickness of their material. The panels of cross-laminated timber at 1 De Haro are 11 inches thick. The columns and beams that support them are hefty and compressed.

Should a stray spark alight — or should an arsonist strike — the idea is that any flames would smolder, not spread.

“These will char around the edges,” Fisher said, standing near the first intersection of panel and beam, “but they’re so large that the structural integrity won’t be affected.”

It’s not that mass timber is trouble-free.

Construction of a university building in Oregon was halted because panels were cracking into fragments, the result of incorrectly applied lamination. Timber high-rises have been announced with fanfare in New York and Portland, then put on hold because of costs.

But for every setback that attracts attention, mass timber’s popularity continues to grow. The architectural firm doing the Pier 70 building, Portland-based Hacker, has designed 16 other mass timber projects.

Besides the emphasis on sustainability, using a material that is the antithesis of paper-thin glass has a more primal appeal.

“This is a way to bring the character of old brick and timber to a project but do it in a new way,” said Steve Shanks of SKS Partners. “It looks good and feels good. We really want to emphasize that.”

John King is The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron