The North American headquarters of Adidas may double in size in north Portland with a planned 2018 expansion.

The German-based footwear and apparel giant, which has seen sales in North America grow rapidly in 2017 and into 2018, announced plans for construction at its North American headquarters to start in late summer or early fall 2018, adding two three-story buildings and a five-story structure for an additional 425,000 sq ft of space.

The Adidas headquarters has already started to burst at the seams of its North Greeley Avenue location on the east side of the Willamette River near Interstate 5. The campus has about 1,700 employees in 360,000 sq ft. The expansion plans more than double the headquarters' size as Adidas looks to expand to 2,800 employees.

Nike, located outside of Portland in Beaverton, is also undergoing an expansion that includes four new structures totaling more than 1.5 million sq ft, opening between early 2018 and 2019.

As part of the Adidas expansion plans, officials met with the local Overlook Neighborhood Association to explain the expansion and attempt to alleviate concerns about overcrowding in the area. One change coming includes Adidas moving its employee store from the current campus to a Montgomery Park building in Northwest Portland, an effort to cut down on traffic in and out of the site.

The new expansion will also include parking that goes multiple stories underground. Along with the new parking, Adidas plans to realign access to the campus and move the delivery area, which will change the traffic pattern throughout the neighborhood.

“We've been experiencing unprecedented growth in North America, with the Adidas brand up 35 percent in 2017," Adidas North America President Mark King said in a statement. "This growth has brought more people to our office, and our Portland workforce has more than doubled in three years, from about 800 to more than 1,700 people. We know this can present challenges, so we’re working quickly to find solutions. We love being part of the Overlook community, and it’s really important to us that we continue being a good neighbor.”

Adidas expects to start construction in fall 2018 and wrap the project in 2020.

Follow Tim Newcomb on Twitter at @tdnewcomb.