Sometimes, one thing leads to another. For instance, this garden structure started with an unusable slope. Architect Bari Thompson of Lake Oswego, Oregon, first created a level terrace, then installed a patio. Thompson, an avid gardener, used the patio as the platform to build the little house shown above.

Instead of buying a barn-style prefabricated shed, Thompson chose to create a structure that would fit in with his home's architecture. To facilitate construction, he made it 8 feet square, which allowed him to use standard 8-foot materials; he cut the door down to 6 feet. All the materials came from a local home supply center.

So that the house would last a long time, Thompson says, "I wanted to use the most rotproof materials I could find." For the walls, he chose 1/2-inch cement backerboard, instead of plywood, and, for the floor, concrete patio blocks. Standard stud-and-joist framing rests on pressure-treated 4-by-6 beams, which serve as footings for the load-bearing side walls.

The roof is covered with composition shingles. Gutters channel rainwater into a 44-gallon plastic trash container, which serves as a cistern supplying the sink inside―an inexpensive plastic storage bin with a drain hole drilled through the bottom. The flower-filled window boxes, irrigated with the rainwater, are made from 1/4-inch backerboard screwed onto a cedar frame.

Painted with masonry paint, the little house holds tools and cheerful garden art. It's a place for potting up annuals and retreating from spring showers; in autumn, bunches of flowers dry on pegs in the rafters.