THE NORTHWEST WASHINGTON Georgian Colonial home had all the right elements for a wonderful back yard -- a goldfish pond, sculpture and a lovely swimming pool. But something was missing. The transition from house to yard was awkward.

With the help of McCartney Lewis Architects, the owners of this elegant home and its back yard, brimming with promise, created a dramatic yet simple outdoor living room. The couple asked Ann McCutcheon Lewis and Jack McCartney to create a graceful transition -- to bridge the gap between indoor and outdoor spaces -- with something that would give a feeling of shelter and openness at the same time. They wanted a terrace, and they wanted some privacy on either side of the house.

To solve the problem, the architects devised a single-story trellis with a gable at the center and two wings. Today, the trellis has a living roof of silver fleece vine with tiny white flowers that soften the lines of the structure without obscuring it. The architects chose to build the trellis the full width of the house, opening up the whole house to the whole yard.

"We wanted to change the proportions of the rear of the house," says architect Ann Lewis. "We wanted to create a more human-scale transition to the garden by making a single-story skeleton in trellis work." With lattice on either end of the trellis, the focus is on the yard itself, elaborately landscaped with the help of Gustin Gardens. The simple trellis has created for the owners of the house a new open-air living room.