How much should seams between adjacent membrane sheets be overlapped?

The recommended overlap for seams between adjacent membrane sheets in radon mitigation systems is typically 12 inches. This overlap ensures a robust barrier that effectively prevents the passage of radon gas and other soil gases through potential gaps. An adequate seam overlap minimizes the risk of gas infiltration, which is crucial for maintaining a safe and effective radon mitigation system.

Using a 12-inch overlap provides a good balance between ensuring an effective seal and managing the material's integrity and installation practicality. It allows for sufficient adhesion and coverage while minimizing the chance of seams lifting or separating over time, especially when considering factors like temperature changes and moisture.

In comparison, lesser overlaps, such as 6 or 10 inches, might not provide sufficient coverage against gas penetration, while an 18-inch overlap may be unnecessarily excessive, complicating installation without significantly improving the gas barrier effectiveness. Thus, adhering to the standard of a 12-inch overlap is essential for optimal performance in radon mitigation efforts.