Despite significant advances in design and construction practices, water intrusion remains one of the most common causes of building repair. Water intrusion can lead to mold, decay, and poor indoor air quality, and affect the durability of the home. Water entering a basement or crawl space can contribute to moisture problems in above grade areas due to increased relative humidity. Even minor omissions during design or construction can lead to significant water damage. Building codes establish minimum requirements for moisture control but don’t always provide sufficient implementation details.
This TechNote provides an overview of essential water management measures and building code provisions that builders should consider to minimize the risks of water intrusion. The focus is on rain and groundwater control practices for foundation and above-grade wall construction. Water vapor migration through building assemblies and corresponding potential moisture problems is the subject of a future TechNote.
The fundamental principle of water management is that exterior water must be provided with a path from the roof to the foundation to drain down and away from the building. Proper drainage and flashing are key to control rain and groundwater intrusion.