Air leakage through exterior walls of washrooms can lead to significant damage to the stud cavity due to the increased humidity in these rooms. All air leakage locations should be sealed off to prevent humid air from flowing into the wall framing and condensing in the stud cavities. Sealing penetrations, corners, and trim is inexpensive and easy to do from inside the washroom. In conjunction with renovations, bathtubs and showers should be installed airtight against the walls.

Typical Interior Air Sealing Locations and Procedures at Above-grade Exterior Washroom Walls:

1. Seal mechanical, electrical, plumbing, and other services penetrating exterior walls with polyurethane spray foam or sealant.
2. During bathroom renovations bathtubs and shower stalls should be installed airtight against the walls and the floor.
3. During bathroom renovations the wall backer-board should be installed airtight.