This story was originally published in Dwell’s November 2013 issue.

In 1991, after Isabel Germain separated from her husband and inherited some money from her mother, she decided to build a one-of-a-kind refuge on a remote beach outside Tongoy, Chile. Luckily, her $20,000 budget went far with her architect of choice: her son, Mathias Klotz.

Klotz—who sketched the layout on an airplane napkin and says that, to date, “it’s the only project I have completed without making changes”—designed the beach house as a low-cost dwelling that requires little maintenance. To this day, the Klotz family still spends the summer and occasional long weekends in their getaway. As for its architectural legacy, Klotz says of his earliest completed project, “It represents what I consider to be the essential aspects of a building.”