Law firm Nixon Peabody is moving its Washington office, which has about 170 attorneys and staff, four blocks north to the corner of Ninth and H Street NW, adjacent to CityCenterDC.

The firm has signed a 15-year lease to occupy three floors at 799 Ninth St. NW, a 10-story building owned by Brookfield Office Properties, said D.C. managing partner Jeff Lesk. The property, which is undergoing renovations, was previously leased by the federal government.

Nixon Peabody’s current lease, at 401 Ninth St. NW in Penn Quarter, is up in 2015. It is the third major law firm that has announced intentions to move to the vicinity over the next two years: Covington & Burling, the District’s largest law firm, has signed a lease to relocate to CityCenterDC in summer 2014. And Arnold & Porter plans to move nearby, to 601 Massachusetts Ave., in October 2015.

The move represents a significant downsizing in the Nixon Peabody’s real estate footprint, from 92,000 square feet to 65,000 square feet — a 30 percent reduction. Although several major law firms in Washington have reduced square footage when moving to new office space recently, Lesk said his firm’s reduction is more dramatic than most.

“Like any business, the number one cost of running a law firm is personnel, but real estate is a significant second place,” he said. “Most law firms, us included, have a shift in mindset. We definitely want to build in opportunity for growth but real estate is too expensive to have too much space in reserve.”

The new office will have a much smaller library, office services and secretarial space, and will likely combine shared space like conference and break rooms.

“This is driven in significant part by having a realistic reset in what’s appropriate real estate spend for a top notch law firm,” Lesk said. “We think it can be significantly less. . .the traditional square footage is not necessary to do a great job serving clients and providing a great workspace.”

The firm considered 23 office buildings across the Washington region, including some in Rosslyn, Southeast D.C. and on North Capitol Street, before deciding on the new Penn Quarter office. It is working with architects at Perkins+Will to renovate the space, in hopes of earning a gold or platinum LEED environmental rating.