A leading national affordable housing developer is moving its downtown Boston headquarters.

WinnCompanies has signed a lease with The Georgetown Co. for a 27K SF, three-story office at One Washington, a 16-story tower near City Hall Plaza, Bisnow has learned. The new deal brings One Washington’s occupancy to 98%.

“WinnCompanies’ growth requires larger office space and the kind of modern, flexible and innovative space that One Washington delivers in a perfect location for our team members, partners and clients,” WinnCompanies CEO Gilbert Winn said in a statement. “We are committed to being headquartered in Boston and we look forward to being at One Washington for the long term.”

The company currently operates a 120-employee, nearly 24K SF headquarters in Six Faneuil Hall Marketplace, according to Perry data. It is expected to move to One Washington in two phases between the end of 2019 and the beginning of 2020.

Staples, Donnelley Financial, Stewart Title, The Housing Partnership, the Massachusetts Bankers Association and Boston’s Dreamland Wax Museum are also tenants at One Washington, owned by The Georgetown Co.

“We are thrilled to have WinnCompanies join the dynamic tenant roster of One Washington, reaffirming their commitment to Downtown Boston and further validating the tremendous energy in and around our building,” The Georgetown Co. Managing Principal Jonathan Schmerin said in a statement.

The downtown tower is in proximity to all four MBTA subway lines via the nearby Government Center, State Street and Downtown Crossing stations. It is also in the heart of a downtown area seeing $6.1B in real estate development, including Bulfinch Crossing across City Hall Plaza, Hub on Causeway, Congress Square, Winthrop Center and the redevelopment of Faneuil Hall.

Cushman & Wakefield Executive Director Peter Fanum represented WinnCompanies on the lease agreement. The Georgetown Co. Vice President Mike Whitman led the leasing efforts internally for The Georgetown Co. Gilbert Winn and WinnCompanies founder Arthur Winn were among the WinnCompanies team members who also worked closely with The Georgetown Co. on the leasing deal.