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Brannan Street has long been one of those thoroughfares you cross while heading somewhere else, with long blocks of stocky blue-collar buildings pockmarked by parking lots.

Now, though, it’s home to a mini construction boom, with three large commercial structures being completed in a two-block stretch near South Park. The newcomers don’t make an architectural fuss, but that’s the point. Instead, they demonstrate that it’s possible to add contemporary buildings to established settings in low-key but comfortable ways.

One of the three, 270 Brannan St., sits within the South End Historic District, which was established in 1990 to identify a loose collection of more than 50 industrial structures “characterized by solid walls of brick and reinforced concrete” that together “are reminders of the maritime and rail activities which helped to make San Francisco a great turn-of-the-century port city.” The other two, 333 and 345 Brannan, rub against the district’s boundaries.

Not only do the latter buildings sit next to each other, they’re both being leased by tech firm Dropbox in a business deal that led to internal redesigns during construction so the floors would connect and there’d be a single main lobby. This adds to the sense that they could be fraternal twins: broad flat boxes five stories tall, clad in red masonry with battleship gray sunshades as eco-friendly window accents. Both stand snug against the sidewalk, though 333 Brannan also comes with an exceptionally civil pair of seating nooks for passersby on Stanford Street, the alley to the east.

In fact, the resemblances are driven by neighborhood zoning and the Planning Department’s desire for a look that’s compatible with the historic neighbors. At 345 Brannan, developed by Breevast, architect Charles Bloszies stretched things out with broad windows and metal spandrels set back slightly from the structure’s skin of long terra-cotta panels.

Next door, William McDonough + Partners was the architect for Kilroy Realty and went for a more tightly syncopated look, with square, punched windows set in thin dark sills that extend 4 inches beyond the surrounding surface of red bricks.

One is elongated, the other precise. Or a musical analogy: andante and staccato.

Closer to the waterfront at 270 Brannan, Pfau Long Architecture took the district tradition of masonry and concrete in a more abstract direction.

Set on a mid-block site with aged structures on each side, the five-story building that will be completed next month features a tall base that showcases bare concrete while above, the thin skin of dappled terra-cotta includes tubes known as baguettes that span the top of each set of windows and play the role of sunshades. By sticking to the historic materials and then flattening them out, Pfau Long and developer SKS Partners play by the rules yet still catch the eye.

As for which one is “best,” that’s a style call for anyone who passes by. Not one of the three is flawless: Some parts of 345 Brannan feel arbitrary, such as an angled bay that lines up with Jack London Alley and the view of South Park beyond, while at 333 Brannan the white joints between the precast brick panels are all too easy to see. On the next block, the baguettes at 270 Brannan look skimpy — as if Pfau Long wanted an excuse to use a product associated with Renzo Piano but didn’t order enough of them.

Nor can the unassuming heft of the nearby warehouses be replicated, or such touches once taken for granted as the rat-a-tat layers of brickwork that accent the cornice of the former Gallo Salame factory from 1907, next door to 270 Brannan. You know the newcomers are newcomers. Better that, though, than pallid mimicry that would look fake from opening day on.

“We wanted something simple and strong, like the existing buildings around here,” said David Johnson, the managing partner of McDonough’s San Francisco office and designer of 333 Brannan — a comment that could be applied to the other two buildings as well.

Another 21st century element is the emphasis on environmentally sensitive design. Both 270 and 333 Brannan are designed to meet the United States Green Building Council’s LEED Platinum rating. The former is shaped around a landscaped courtyard with an angled glass roof that will steer rainwater into a cistern so that it can be used for irrigation. The latter includes outdoor pavers that were produced in a lab in a weeklong process similar to how coral reefs grow, each paver formed in a mold where sand is mixed with nutrient-rich liquids.

It’s the first commercial application of the process in America by the firm BioMason, according to Johnson.

These elements, like the textured presence of all three buildings, are keyed to long-term durability rather than short-term flash. In an era when local architectural fashions too often indulge in sleek glass or randomly stacked bays, looking toward the future is a welcome trait indeed.

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

John King is The San Francisco Chronicle's urban design critic, taking stock of everything from Salesforce Tower to sea level rise and how the pandemic is redefining public space. A two-time Pulitzer Prize finalist and author of two books on San Francisco architecture, King joined The Chronicle in 1992 and covered City Hall before creating his current post. He is an honorary member of the American Society of Landscape Architects.