IT’S ONE OF those Ballard blocks where perfectly pruned perennial gardens border wild and weedy hippie homes. Second in from the corner sits a three-story cube with steel balconies slung in front of the top two levels, red and pea-green patio furniture popping against the industrial gray facade. Approach it from the street, and you’d never know that the back half of the house is a 1,300-square-foot, periwinkle bunga...