Microsoft announced last week that it will begin construction on a massive overhaul and expansion of its facilities in Redmond.

Microsoft, which settled in the city in 1986, will be replacing portions of its campus and create 18 new buildings.

This will include a total of 6.7 million square feet of renovated workspace — of which 2.5 million will be new — $150 million in transportation infrastructure improvements, new sports fields, public spaces and green space.

Once it is finished, the campus will have 131 buildings that will house 47,000 employees and room to expand and accommodate 8,000 more.

“It’s an investment that’s good for our employees, good for the Puget Sound community, and makes good sense for our shareholders,” Microsoft President Brad Smith said on the company blog with the headline, “Investing to grow right here at home.”

Smith added: “We are not only creating a world-class work environment to help retain and attract the best and brightest global talent, but also building a campus that our neighbors can enjoy, and that we can build in a fiscally smart way with low environmental impact.”

The project will break ground in the fall of 2018 and take between five and seven years and is slated to come online around the time the Eastside receives its East Link light rail stations in 2023 and 2024.

A 50-foot-wide pedestrian bridge will link the campus to the light rail stations, which is a scaled-up version of the 15-foot bridge originally funded by Sound Transit.

Redmond Mayor John Marchione praised the expansion and the company’s decision to continue expanding in the city.

“The reimagining of the Microsoft campus highlights their global leadership in technology and strengthens both Redmond’s and the region’s reputation as a hub for ingenuity,” he said.

Microsoft only notified the city of its plans the night before, but Marchione said the company is still operating under a 20-year development and mitigation agreement that was approved by the city in 2005.

No construction permits have yet been submitted by Microsoft.

“We prize our relationship with the city of Redmond and will work closely with officials on the approval for campus and building architectural designs, engineering, building permit review and land use code compliance. As a Zero Waste Certified campus we will continue to focus further on waste-reduction initiatives,” Smith said.

The announcement has also received praise from county officials.

King County Executive Dow Constantine released a statement on Microsoft’s decision.

“Microsoft’s bold investment in 2.5 million square feet of new office space demonstrates the company’s clear understanding that this is the best place in the nation to grow,” he said in the statement. “For more than 30 years, Microsoft has fueled a regional economy built on knowledge, innovation, and creativity. With this major new investment in its Redmond campus, Microsoft strengthens its partnership with King County, it’s commitment to Central Puget Sound, and our future as a leading global technology center.”

Former Bellevue mayor and current King County Councilmember Claudia Balducci praised the region for its commitment to improving infrastructure, such as East Link, which is a draw for companies like Microsoft.

“Our region is prospering due to companies like Microsoft that value what Puget Sound has to offer,” Balducci said in a statement. “Microsoft’s plan to expand their headquarters in Redmond shows the strong relationship the company has with our region and highlights its commitment to improving and building upon the success they have had here.”

She added the region has done their part to promote “economic opportunity and prosperity” by building out a cohesive transportation network anchored by a regional light rail system. The East Link light rail extension will open near the Microsoft headquarters in 2023.

“I am proud of the work we have done to encourage this development and the path it has created for Microsoft to recommit to the Puget Sound area,” Balducci said. “This is exactly the kind of outcome we were working for when we first planned light rail expansion to the Eastside. Companies like Microsoft see the benefits of having their employees have access to high capacity transit. The investments we have made are validated by [this] announcement.”

The renovations include modernizing office spaces. When it was built, identical offices and natural light were incorporated into the design but the buildings also have low ceilings and many hallways, a press release from Microsoft said.

The rebuilt campus will focus on a more communal space for employees. It will feature a two-acre plaza with space for up to 12,000 people to gather and various sports fields, including a cricket pitch.

“As Microsoft continues to create the tools and services that are shaping the future of work, we can’t think of a better time to modernize our campus into a model of ingenuity and innovation,” Smith added.

Redmond Reporter editor Andy Nystrom contributed to this story.