Boston University School of Law has spent the past decade planning a new building, and now it is moving forward due in part to an $18 million donation from Sumner Redstone.

Redstone, a former law school faculty member, is executive chairman of CBS Corp. and Viacom Inc.

Plans call for a five-story building next to the school’s existing Law Tower, and for the 50-year-old tower to undergo a major renovation during the 2014-15 academic year — after the new Sumner M. Redstone Building is slated to open.

The new, 93,000-square-foot building will house most of the law school’s classrooms as well as student study space and meeting areas. It will allow the expansion of the law library and offer more room for clinical, transactional and executive education programs. A glass-encased atrium is intended to serve as the new social center of the law school.

“At a time when legal education is facing many challenges, Mr. Redstone’s gift is a tremendous vote of confidence in the future of legal education at Boston University School of Law,” dean Maureen O’Rourke said in announcing the donation. “Thanks to his generosity, we will now be able to build a first-rate facility to complement the superb educational experience that our students receive.”

Redstone earned a bachelor of laws degree from Harvard Law School in 1947. He began teaching entertainment law at Boston University in 1982 and received an honorary Doctor of Laws degree from that school in 1994. His daughter graduated from the law school in 1978.

“Boston University School of Law is one of the finest institutions of legal scholarship in the world and deserves a home that will enable it to continue to innovate and build on that legacy,” Redstone said in a written statement. “As a former faculty member, native Bostonian, and the proud parent of a BU Law graduate, I could not be more pleased to provide this gift that will benefit generations of future students.”

Work on the site began this summer, with construction expected to get underway in May. The project is being funded primarily through a combination of donations and university funding.

A law school spokeswoman said the school has not yet calculated t he total cost of the new building and the renovation.

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