Matt and Steve examine an unconventional floor assembly in a Passive House-certified, zero-energy ranch home in Climate Zones 4A/5A. Instead of a conventional concrete slab, the “slabless” slab uses doubled floor sheathing supported by free-draining gravel, reducing cost, construction time, and environmental impact. The gravel provides a capillary break and reservoir for water, while high-compressive-strength EPS Type IX insulation supports the assembly. Matt and Steve explain how materials can perform multiple functions, including contributing to airtightness, and why the moisture-control layer’s location is critical for protecting the sheathing. Using a real-world example, they discuss how a basement flood tested the assembly’s resilience. The episode also covers termite protection, vapor management, and continuous exterior insulation.