Outerbridge Horsey Associates, PLLC

Dumbarton House (c. 1800) is a house museum in the Federal style and the national headquarters of The National Society of The Colonial Dames of America. The building is located in the Georgetown National Landmark Historic District of Washington, D.C.

This project included renovations to the administrative offices and support spaces to the east and west pavilions, and the collection storage located in the basement. In 2015, date the balustrade on the east terrace was replaced by an equally decorative balustrade in order to meet the requirements of the building code.