Maintaining one’s own space after can be tricky for a couple, especially if they are artists of a certain age, set in their ways. This was the case with Eleanor Lanahan, a 63-year-old filmmaker, writer and illustrator known as Bobbie, and John Douglas, a 73-year-old filmmaker and political activist. Ms. Lanahan smokes; Mr. Douglas does not. She likes pretty, traditional furnishings, while he is all about simplicity and comfort. She cares about architecture; one of Mr. Douglas’s suggestions, as they were trying to figure out their living arrangement, was that she put up a big billboard of whatever kind of house she wanted — say, something with a big old gambrel roof — and they live in an old galvanized shed behind it. They shuttled, for 18 years, between his cabin in Charlotte, Vt., overlooking Lake Champlain, and her three-story house in Burlington some 30 minutes away, never able to agree on a home they could share. Finally, skyrocketing taxes forced Mr. Douglas to give up his place. Ms. Lanahan’s house had a rental apartment, and Mr. Douglas might have easily moved into that. Instead, they built a separate studio for Mr. Douglas, with two bedrooms and a bathroom that is connected to Ms. Lanahan’s house with a bridge: a 20-foot plant-filled overpass. The cost of the addition was about $366,000.