One World Trade Center is on a roll with another new tenant.

Servcorp has signed a 15-year lease for 34,775 square feet, taking the entire 85th floor, The Post has learned.

The Australia-based company, which provides both co-working space and virtual offices, expects to spend at least $1.8 million on a build-out.

The new deal means the tower’s 3 million square feet are nearly 57.5 percent occupied, as each floor works out to roughly one percent.

Servcorp represented itself in the negotiations for its fourth Manhattan location that already include downtown at 17 State St. and two in Midtown at 1330 Ave. of the Americas and the Seagram Building at 375 Park Ave.

Robert Becker represented the Durst Organization in the deal. Asking rents on the high floors range from $75 to $100 per foot, depending on the floor.

“A number of deals are in the hopper,” said one source of the tower, which is already open for tenant buildouts, including Condé Nast and the US General Services Administration, and will have a grand opening later this fall.

As The Post’s Steve Cuozzo reported, Hugo Boss is in early talks and KiDS Creative leased the 87th floor of 37,500 square feet at a rent of more than $90 a square foot.

Another tenant, the China Center, is negotiating to move from space on the 64th through the 69th floors, to the 88th through 90th floors, which would mean less space at a higher rent.