Roof underlayment is a water-resistant or waterproof barrier installed directly onto the roof deck (wood sheathing) before shingles or other roofing materials are applied. It provides a secondary, critical layer of protection against water infiltration from ice dams, wind-driven rain, and leaks, ensuring the home remains dry.
Key Aspects and Usage Examples
- Secondary Protection: Acts as a backup barrier if the outer roof covering (shingles) is damaged by wind or rain
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- Ice and Water Shield: Self-sealing, rubberized membranes used in vulnerable areas like valleys and eaves to prevent leaks from ice dams.
- Deck Protection During Construction: Safeguards the roof deck from moisture during the installation process, protecting it for days or weeks before the final roof material is applied.
- Code Compliance & Fire Rating: Helps meet local building codes and contributes to the overall fire resistance rating of the roof system.
