How much must sheathing membrane and wall finish overlap the flashing?

The requirement for the sheathing membrane and wall finish to overlap the flashing by 3 inches or 75mm is critical in providing effective water drainage and preventing water intrusion. This overlap ensures that any water that runs down the wall or collects at the top of the flashing is diverted away from the building envelope.

A 3-inch overlap allows for a sufficient amount of material to create a barrier against moisture penetration, considering factors such as potential wind-driven rain and the need for a robust seal. This measurement aligns with best practices in building codes that aim to improve the durability and integrity of constructing walls in various weather conditions.

By utilizing a 3-inch overlap, builders can ensure that the flashing functions effectively, mitigating the risk of moisture-related issues such as rot, mold growth, and structural damage over time. This design consideration is essential for long-lasting performance and maintaining the safety and comfort of the building environment.