Illustration Source: CHBA Manual, Fig. 10.9, Pg. 164

Sealing Exposed Floors:

Maintain the air barrier system at cantilevered floors by:

1. Sealing any and all joints in the structural components
2. Covering the components with an air barrier material and sealing to the adjacent air barrier

The most common approach is to use the plywood subfloor as the air barrier by sealing all penetrations, joints, and seams, and by sealing it to the adjacent air barrier material.