University officials say - for the school's 30,000 students - the union and it's restaurants, lounge spaces, and game room functions as the campus living room.
"Hangout, relax, spend time together and kind of participate in campus life," says Bill Olmsted, associate executive director for Union WELL Inc., the campus auxiliary that runs the University Union and the school's health and fitness center.
He says the current 40 year old building, at 183,000 square-feet, is too small.
"You would see students sitting on the floor, lining hallways, sitting in stairwells and trying to find any available space that they can," says Olmsted.
Under the new expansion plan, the building will grow by 71,000 square feet and include a premium coffee venue and more conference spaces. Money for the project will come from student fees. No state funds will be used.
Construction is expected to start in the first-quarter of 2017 and be finished by August 2018.
The expansion is one of several ongoing campus construction projects. Others include new student housing and a state-of-the-art science building. Olmsted says the university is staggering construction on those projects to keep as much of the campus open to students as possible.
"There will be some inconveniences, as there typically are when there's construction, but we're trying to minimize those as much as possible," says Olmsted.