The brief was basic: a simple guesthouse where a family of five could live for a few years while the architecture firm Bohlin Cywinski Jackson designed their main residence. “Since we were living out in the forest”—a wooded, 482-acre plot at the edge of Bend, Oregon—“we wanted a house that felt like we were living outside and that was resistant to fire,” says James Verheyden, a hand surgeon. He and his wife, Jean, an otolaryngologist, also hoped to build the 2,084-square-foot structure efficiently and, given its future role as a guesthouse, somewhat affordably. Besides those guidelines, they gave the firm carte blanche. “When someone comes to me for an operation, they don’t tell me how to operate,” James says.

Fortunately, the residents and architects saw eye to eye almost immediately. “Exploring the way things are assembled—that was the family’s interest as well as ours,” says Robert Miller, the principal in charge of the project. He was surprised and delighted, upon visiting the Verheydens’ previous residence, to see their then-eight-year-old son’s bedroom “filled with science experiments and contraptions” and to discover that James and Jean, both doctors who work at a micro level daily, were equally fascinated by macro structures and design.

Miller proposed that the guesthouse be a prototype for the larger main house and swiftly suggested a modular approach—a natural evolution of the firm’s design sensibility. “It’s in our DNA to think about the tectonics of architecture,” he says. “Our roots are in expressing how buildings come together. When we started talking about modules, a lightbulb went off.”

The architects developed a standard, repeatable, four-foot-wide bay that makes clever use of economical, readily available materials. The components—open-web steel trusses, full sheets of plywood, laminated veneer lumber, and an insulated aluminum window system from Milgard—were shipped directly to the property and installed by a crew of contractors onsite. The resulting residence is linear and long, with an open- plan kitchen and living space, three bed- rooms, and an office with views over a pine forest and the Cascade Range. The exterior is clad in Minerit HD fiber cement panels, left unpainted but punctuated by a bright green entrance ramp and cherry-red door that together form a visual exclamation point on an otherwise subdued facade.

Miller is pleased with their experiment. “This approach—using prefab components and making use of standard widths and thicknesses of available materials—let us customize the home but shave time and cost, giving us a custom result at a lower price,” he says. And the Verheydens are perfectly content in their scaled-down abode, which cost about $225 per square foot, including the foundation. “It shows you don’t have to use expensive materials to have a warm, inviting, rich feel,” says James. “Every time you turn around there’s something new or unexpected that catches your eye.”