Talk title: "Drain, Drain Go Away"
John Straube is a professor in the Department of Civil and Environmental Engineering at the University of Waterloo, where his research focuses on building enclosure performance, moisture management, and durability. In this talk from the Westford Symposium, he digs into the physics of water drainage in wall assemblies: how much rain actually needs to drain off roofs versus walls, why historic absorptive claddings like stucco and brick behave differently from modern non-absorptive materials like aluminum composite panels, and what happens to water once it's running down a drainage gap. Drawing on lab testing with drip-edge rigs and precision flow measurement, John challenges some long-held assumptions about gap sizing, showing that small gaps can drain plenty of water and that the real reasons behind bigger gaps are dimensional tolerance and ventilation rather than drainage capacity. He closes with an audience Q&A on saw-cut kerfs, WRB perforations, and the difference between drainage problems and drying problems.