ALL TOO OFTEN, an addition on the back of a house is more like an intrusion. A quick drive down any Washington alley will confirm that people who need more space tend to stick something on the back that solves their problem but has no architectural appeal. Architect Tom Manion designed an addition for a family who wanted a recreation room on the lower level, a garden room and a larger kitchen on the first floor and a larger bedroom and a bath on the top floor -- all this on the back of a Federal-style town house in Georgetown.

His addition is distinguished by its distinctive facade. The front of the house remains classically Georgetown, but the rear is dramatic and asymmetrical. The garden room floor is covered with marble. The walls are glass, separated into dramatic panes. Atop the garden room portion of the addition is a greenhouse glass roof. The same pattern of glass forms the wall of the second floor, which is part of a two-story atrium.

So the rear of the house presents two complicated but integrated faces: a solid asymmetrical bay window in the kitchen topped by a small peaked roof, and a dramatic glass-enclosed garden room, making this an out-of-the-ordinary addition.