Window and Door Flashing: Code Requirements and Best Practices (TechNote)

This TechNote provides an overview of building code requirements and best practices for flashing at window and door frames. The focus is on common flashing applications for new construction. Although each window/door manufacturer may have its own set of flashing instructions, the strategies and general principles apply to the vast majority of flashing situations. This TechNote includes Flashing 101, terminology, code considerations, design considerations, and recommendations.

Flashing is a water-resistant product that prevents water penetration at the gaps between the window/door frame and the rough opening.

TechNotes: Best Practices for Home Builders
In recent years, building codes for energy efficiency and related standards have been amended to require greater amounts of insulation in exterior wall and roof assemblies, including continuous insulation on exterior walls, higher levels of building air tightness, and mechanical ventilation.
NAHB’s Construction Technology Research Subcommittee worked with Home Innovation Research Lab to develop these TechNotes to help builders navigate these new code requirements and implement best practices to avoid building performance issues related to interior humidity levels, condensation in wall and roof assemblies, and interior air quality.