The exterior of the house is a mid-century modern take on Norman Revival architecture. When originally built, it was very much of the Victorian (Queen Anne) style; it had high gables, extensive verandahs, and a liberal use of gingerbread trim. A turret was added by the Edwards family in 1907. After it was decided in 1950 the house would become the official residence of the prime minister, the turret, widow's walk, trim, main gable at the front, verandahs, and porte-cochère were removed and an extension added to the east. The interior was gutted, save for part of the dining room.