The ranks of elite Georgetown hotels may be swelling.

A joint venture between two D.C. companies, Castleton Holdings Inc. and ICG Properties LLC, has attracted an undisclosed high-end, boutique operator for a 50-room hotel in the former headquarters of the American Trial Lawyers Association, 1050 31st St. NW.

Castleton bought the property from the association in January 2008 for $18.3 million, and ICG became an equal partner earlier this year, according to ICG principal David Stern.

Georgetown is already home to high-end hotels including the Four Seasons, The Ritz-Carlton and St. Gregory Luxury Hotel & Suite.

But Stern's partner, Stylianos Christofides, said there was still room for "ultra high-end" lodging for business travelers and tourists.

Although the partners will not identify the hotel operator they have selected, Christofides said, "The hotel concept we're looking at is unlike anything currently in D.C."

The freestanding five-story brick building on 4,400 square feet along the Chesapeake & Ohio Canal path is vacant. The developers plan to begin the rehab at the end of this year and open the hotel in 2011, but still need financing.

"We're taking one step at a time, and there is significant equity in the project through the joint venture," Stern said.