A cedar roof moisture barrier is a protective layer installed beneath cedar shakes or shingles to reduce water penetration into the roof structure. It serves as a secondary defense system beneath the visible roofing surface.
Moisture barriers are especially important in cedar roofing because natural wood systems are not fully sealed and depend on overlapping layers for water shedding. Wind-driven rain, snow, or aging shakes can occasionally allow moisture beneath the cedar surface.
Modern moisture barriers are commonly made from synthetic waterproofing materials that resist tearing, UV exposure, and long-term moisture contact.
Proper installation around valleys, penetrations, ridges, and roof edges is essential for maintaining continuous protection.
Moisture barriers significantly improve leak resistance and help protect decking and structural components from hidden water damage.
