Roofing underlayment is the hidden layer of protection that keeps your roof system strong and resilient. While shingles are the visible shield, underlayment is the backup defense against leaks, ice dams, and weather damage.

• Secondary Protection: If shingles are damaged or displaced, underlayment prevents water from reaching the roof deck.
• Weather Resistance: It protects against wind-driven rain, snow, and ice during installation and throughout the roof’s life.
• Durability: Proper underlayment reduces risks of rot, mold, and costly repairs.

🧊 Types of Ice and Water Shield

Ice and water shield is a self-adhering, rubberized asphalt membrane designed for vulnerable roof areas.

• Standard Ice & Water Shield: Ideal for valleys, eaves, and roof edges where ice dams and pooling occur.
• High-Temperature Ice & Water Shield: Built for metal roofs and hot climates, resisting adhesive breakdown under extreme heat.
• Granular Surface Ice & Water Shield: Provides traction during installation and is common in colder regions.

📜 Types of Felt Paper

Felt paper (tar paper) is a traditional underlayment made from asphalt-saturated mats.

• 15-pound Felt: Lightweight, easy to install, but less durable.
• 30-pound Felt: Thicker, stronger, and offers better moisture resistance.
• Synthetic Felt: Modern alternative that is lighter, tear-resistant, and more durable—but not always the right choice.

🔥 When to Use High-Temp Ice and Water Shield

• Metal Roofs: Metal absorbs and radiates heat, requiring high-temp membranes to prevent adhesive failure.
• Low-Slope Roofs: More prone to water pooling, so stronger waterproofing is essential.
• Hot Climates: High-temp shields withstand prolonged sun exposure without degrading.

🚫 When Not to Use Synthetic Felt Paper

Synthetic felt is popular, but it has limitations:

• Hot Roofs: In systems where insulation is directly against the roof deck (no ventilation gap), synthetic felt can trap heat and fail prematurely.
• Underventilated Roofs: Without proper airflow, synthetic felt may degrade faster, leading to moisture and heat buildup issues.
• Budget Considerations: It’s more expensive than asphalt felt, and in some cases, traditional felt provides adequate protection at lower cost.

✅ Final Thoughts

The right underlayment depends on climate, roof type, and ventilation. Use ice and water shield in vulnerable areas, and opt for high-temp versions under metal roofs or in hot climates. Felt paper remains a reliable option, but avoid synthetic felt on hot or underventilated roofs where performance can suffer.