Restoring an iconic, historic modernist house designed by an internationally acclaimed architect can pose many technical and philosophical challenges for a project team. Often, these buildings have an Achilles heel detail where a critical design flaw has not stood the test of time, creating problems such as leakage, deterioration, and structural degradation. In these instances, a key question is: How can we design a repair to succeed where the original failed, while maintaining the master’s design and aesthetics. Conversely, centuries-old iconic historic houses that have stood the test of time often have a few remarkable details that were key to long-term durability.  These details have much to teach us about designing for durability, if we only take the time to study them closely and understand why they have worked so well for so long. In this course, we will explore how the details of iconic historic houses, both traditional and modernist, have contributed to their durability or lack thereof, and discuss what we can learn from the successes and failures of these details, not only for preservation, but also for new design. The presentation will focus on one key detail from each of these six iconic historic houses, analyze it to show why it succeeded or failed, and in the latter case, share the detail we designed to rectify the problem, while respecting and maintaining the historic appearance.