United Nations ? U.N. Secretary General Ban Ki-moon and other staffers will have to shift their offices to the lawn in front of the organization’s hulking headquarters while workers renovate and clean up the 55-year-old landmark building, the director of the project said Monday.

While the 39-story Secretariat building and adjoining General Assembly Hall undergo a planned $1.9 billion interior makeover, Ban and other U.N. employees and delegates will remain on the U.N. campus, housed in a temporary conference building on the north lawn, Michael Adlerstein said.

Adlerstein, a former architect for the National Park Service who is heading up the five-year renovations, said work is due to start next spring.

While the buildings contain art and other cultural gems from around the world, they also have lead paint, asbestos insulation, worn-out interiors and outdated electrical wires and plumbing.

After renovations are complete, the United Nations “will not only be a safer, healthier, greener and a more secure place – our renovated workshop for peace will also stand out as a symbol for building a revitalized United Nations for a better world,” U.N. deputy spokeswoman Marie Okabe said.