M.A. Mortenson Co. has purchased an office building next to its Golden Valley headquarters as it looks to expand its campus.

According to an electronic certificate of real estate value that became available last week, North Wirth Associates, an affiliate of Mortenson, purchased the four-story building at 4050 Olson Memorial Hwy for $8.3 million from real estate development and property management firm Ted Glasrud Associates.

With the new purchase, Mortenson owns all three buildings at its campus and the parking lots that come with them. Last year, the construction and development company announced it would build a larger parking ramp and new six-story office building for its growing workforce.

"We are outgrowing the current footprint at our Golden Valley campus and have been exploring expansion options at our headquarters," said spokesman Cam Snyder, in an email. He added later, "The purchase allows for further room to grow as we continue to evaluate the expansion and site improvements previously discussed with the City of Golden Valley."

Currently, Mortenson has about 600 employees who occupy 185,000 square feet in two buildings at its headquarters.