The black zinc panels that form the exterior of U.S. Bank Stadium leak more than previously revealed and must all be replaced at a cost of $21 million over the next two years, according to a settlement announced Friday.

The costs will be split among the building's general contractor, Golden Valley-based M.A. Mortenson Co., and seven others. Neither Minnesota taxpayers nor the Minnesota Vikings will pay to replace the panels, which came undone and leaked months before the $1.1 billion building opened in August 2016.

"At the end of the day, we will have a superior solution," said Michael Vekich, chairman of the Minnesota Sports Facilities Authority (MSFA), the public body that oversees the building on behalf of taxpayers.

Although moisture problems surfaced on the building as early as 2015, stadium officials and Mortenson publicly downplayed questions about the scope of the problem. "I'll be honest with you, we're embarrassed by the fact this building has had the issues it's had," said John Wood, the Mortenson senior vice president who oversaw the project.

He added that Mortenson can't change what happened, but the company can "do the right thing" and fix it.

Vekich and Wood worked to portray the development as an amicable solution to an unfortunate problem.

But the reality is that the stadium, not yet four years old, will be visibly under repair for at least another two years because a signature design element failed.

Wood said the leaks weren't substantial. Water wasn't gushing into the building, and it could easily be mopped up.

"Nonetheless, it gave everyone reason to be concerned," he said. "We could see some repetition of these problems."

Vekich said when he arrived in the summer of 2017, the panels had been reinforced, but questions remained about whether that would be enough to address the leaks long term.

Mortenson requested mediation in the fall of 2017 and discussions began in April 2018.

Wood called the response "very Minnesotan." The situation could have "easily deteriorated into a fight and a lawsuit dragging out for years," he said.

The mediated settlement came out of closed-door talks with the Mortenson Co., architect HKS Inc., M.G. McGrath Inc., Custom Drywall Inc., TRI-Construction, Larson Engineering Inc., Thornton Tomasetti Inc. and Studio Five Architects.

None of the parties knows what any other party will pay, and they are contractually prohibited from telling one another the amounts.

Even before the MSFA approved the mediated settlement at its monthly meeting Friday, scaffolding had been erected on the northwest corner and removal and replacement work had begun.

The nature and scope of discussions wasn't revealed until recent weeks when Vekich said the sides were close to an agreement.

In all, 250,000 square feet of the exterior will be torn off and replaced.

Wood said the panels and material had been tested before construction, but conditions, especially on the northwest prow, were more intense than expected.

The loose panels, moisture and leaks "gave all of us reason to question whether or not this exterior wall system was going to pass the test of time," he said.

Over the next two years, workers will go section-by-section to remove panels and replace them.

The new zinc panels will be of similar color and dimension. Wood said nine out of 10 people wouldn't notice the difference.

The existing zinc panels were designed to act as a rain screen, allowing some water through them, Wood said.

The replacement panels will be designed to repel water.

Also, before the replacements are installed, a second waterproof membrane will be added to the existing shield on the building.

So there will be two water barriers instead of one, plus the panels, which all are designed to keep the building dry.

Vekich and Wood said the construction will not interfere with events or Vikings games at the stadium.

The Vikings, who are not a part of the settlement, issued a written statement saying they appreciated the work "to find a permanent solution to the exterior enclosure that preserves the long-term future of this community asset."

Before construction, the main concern for the building was whether the transparent plastic roof could withstand Minnesota winters.

The roof has held up through cold, heat and storms, and it repelled snow accumulation as designed.

In 2012, the Legislature approved paying $348 million in state funding for the stadium and Minneapolis agreed to pay $150 million. The Vikings covered the rest.

Twitter: @rochelleolson