Cedar roof underlayment is the protective moisture barrier installed beneath cedar shakes or shingles and directly over the roof decking. It acts as a secondary waterproofing layer that protects the structure if water penetrates the outer cedar surface.
Underlayment is particularly important in cedar roofing systems because cedar materials naturally expand and contract with moisture and temperature changes. This movement can occasionally allow wind-driven rain or melting snow to pass beneath the shakes.
Modern cedar roofing systems often use synthetic underlayment due to its improved durability, tear resistance, and moisture protection compared to traditional felt paper.
Proper underlayment installation includes overlapping seams and careful detailing around valleys, penetrations, and roof edges to maintain continuous water protection.
A high-quality underlayment system significantly improves the long-term performance and leak resistance of cedar roofs.
