Construction has begun on a steel net to prevent people from jumping off the Golden Gate Bridge, after years of debate over whether such an obstacle would mar the bridge’s romantic image.

For at least the next two years, crews will toil throughout the night to build a coarse web of marine cable beneath the Art Deco span that is both an international symbol for engineering beauty and a magnet for suicides. Bridge officials documented nearly 1,700 people leaping to their deaths since the landmark opened in 1937 — including 14 so far this year.

The bridge is one of the world’s top destinations for suicides, said Denis Mulligan, general manager of the bridge district. Mental health experts hope that when the nets are completed in 2021, the deaths will abruptly stop.

“The hope is that these suicides will go down to zero,” Mulligan said.

Oakland companies Shimmick Construction Co. and Danny’s Construction Co. won the contract to design and build the net for $211 million — about three times what the Golden Gate Bridge, Highway and Transportation District Board of Directors had proposed when it put the project out for bid in 2014.

At that time, the design team did not quite grasp the complexity of the design and engineering, or the challenge of lugging heavy equipment in a brutal environment 250 feet above the water, said the bridge’s chief engineer, Ewa Bauer-Furbush. The transportation district cobbled together funding from federal, state and regional sources, with large shares coming from Caltrans, the Metropolitan Transportation Commission and the bridge district itself.

The net that the two construction firms envision is a meticulous piece of sculpture, comprising 385,000 square feet of marine-grade stainless steel — the equivalent of seven football fields — that will be hung 20 feet below the bridge’s public walkway on steel cantilever brackets. Those brackets, painted the same international orange as the span and towers, will be spaced 50 feet apart and protrude about 20 feet from the side. The mesh will be gray to match the frequent fog that embraces the bridge and the water below.

“So the color will camouflage it,” said Bauer-Furbush said.

Ideas for a suicide barrier began gestating as far back as the 1950s, when officials considered stringing barbed wire above the rail. In the 1970s and ’80s, the bridge district studied other proposals, mostly railings or fencing with horizontal wires that become slack and harder to maneuver as people climb up.

But it was difficult to build consensus for a barrier, Mulligan said, because most models hit resistance from neighborhood groups and preservationists who worried about sullying the bridge’s aesthetics and majestic views. Some critics argued that a steel net alone wouldn’t stop people from using the bridge to end their lives — if a plunge from the bridge were blocked, they would simply go elsewhere.

Studies from Harvard University and UC Berkeley rebut that argument, showing that 9 out of 10 people who are stopped from committing suicide do not kill themselves at a later date.

Then there were engineers who opposed the barriers, saying the extra weight would cause the colossal span to topple in a strong wind. The bridge district allayed those concerns by installing equipment to beat back winds that would otherwise rattle the roadway.

“We dispelled each and every one of those arguments,” said former Marin County Coroner Ken Holmes, who became a stalwart proponent of suicide barriers after handling hundreds of bridge deaths.

Nonetheless, it took years, a shift in societal attitudes and a change in the composition of the bridge district board to get the barriers approved.

“Our board tends to reflect society’s values and the broader conversation about suicide,” Mulligan said. With suicide rates climbing around the country, he said, people now see the need for a new form of intervention — beyond the security staff who patrol the bridge looking for lost souls.

“People began to realize that there really is a way to slow down the horrible carnage on this monument,” Holmes said.

So crews have begun their work, installing ladders and platforms that will allow them to go beneath the bottom chord of the suspension bridge, where they will string the net. Meanwhile, factory workers across the country are assembling the net’s parts. The brackets will come from a large steel fabricator in Oregon, while workers at a plant near Chicago spin steel wires into rope for the lattice.

Each of those pieces will be shipped to a yard in Richmond, where crews will practice installing all the components on land.

When the barriers are finished, 2½ years from now, officials say the bridge will be as beautiful as ever — its orange towers and suspension cables set against Angel Island, the burnt umber hues of the Marin hills, and the glassy surface of the bay.

But it will no longer entice those in despair, Holmes said — “that’s our fervent hope.”

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan