Do I need a vapor barrier in my bathroom?

Yes, you need a vapor barrier in your bathroom, but the type and placement depend on your specific wall construction and renovation scope. Vapor barriers are crucial in Ottawa's climate to prevent moisture from penetrating wall cavities and causing mold, rot, or structural damage.

For most bathroom renovations in Ontario, the vapor barrier goes on the warm side of the insulation - typically between the insulation and the drywall. This is usually 6-mil polyethylene sheeting that creates a continuous moisture barrier. The barrier must be properly sealed at all joints, penetrations, and edges to be effective. Any tears or gaps can allow warm, humid bathroom air to reach cold surfaces inside the wall where condensation forms.

Modern building science has evolved beyond simple plastic sheeting in some cases. Many contractors now use "smart" vapor retarders that adjust their permeability based on humidity levels, or they may recommend different approaches like spray foam insulation that acts as both insulation and vapor barrier. The Ontario Building Code requires vapor barriers in heated spaces, and bathrooms with their high humidity levels are particularly critical.

Ottawa's climate considerations make vapor barriers especially important due to our cold winters and temperature differentials between heated indoor spaces and exterior walls. Improper vapor barrier installation is one of the leading causes of moisture problems in renovated bathrooms. If you're doing tile work, remember that tile and cement board are not vapor barriers - the barrier goes behind these materials.

For any bathroom renovation involving wall framing or insulation work, City of Ottawa requirements may vary - confirm with your licensed contractor who can ensure proper installation and code compliance. Want to discuss your specific project? We offer free consultations to assess your vapor barrier needs.