Situated on a promontory overlooking Maine’s Boothbay Harbor, this 1915 house had good proportions, a protective roofline, and a view over the water. So architect Rob Whitten winced when the owners asked him to winterize it and add on. “Many such cottages have been brought to their knees by people wanting to turn them into four-season residences,” he says.

What the clients received instead was a separate master quarters that can be used year-round (see "Pattern Play"). He kept the main cottage simple, stiffening it structurally and insulating from the outside to retain its interior character. Pushing out the wall 6 feet in the kitchen made space for an island on one side of the room, plus a 5-foot-by-5-foot pantry tucked in a corner. He also enlarged an opening to the dining room, which got a new bay, and cut a passageway between the kitchen and the living room. A refined-rustic material palette—wood-paneled walls, recycled heart pine flooring, a farmhouse sink, and cherry cabinets—imparts a sense of comfort and shelter. A simple band of windows rounds a corner over the sink.

Rigid foam insulation in the walls and spray foam in the attic help extend the season by a few months. “The main cottage can be used from May to mid-October,” Whitten says. “At that point you should give it up; summer’s over.”