The cottage, which won a top design award last year from the American Institute of Architects, is technically called an "accessory dwelling unit," or A.D.U. Portland has been ahead of the curve in allowing these smaller housing units, which are illegal in many cities and towns under current zoning rules.
They certainly are not seen as design statements; when such units are built in garages or basements, they tend to be dismissed as "granny flats."
The success of the cottage, designed for Ann Wilson, 68, an interior designer, left its architect, Ben Waechter, amazed. "It was dramatic to get an honor award for such a small project," he said. "Portland has always encouraged a limited growth boundary, so this will encourage density in the center."
The cottage, known as Garden House, is hidden behind Ms. Wilson's 1924 gabled bungalow, which she now rents to the older of her two sons. The cottage's silhouette looks crisply modern: an upward-pointing arrow in a garden setting. The arrow shaft has open-plan living spaces; horizontal windows are the only breaks on its south side; and wide floor-to-ceiling doors and windows open to outdoor living space on the east and west sides.