Choosing the right roofing underlayment is crucial for protecting a home from water damage and ensuring roof longevity. Two of the most common materials used are roofing felt and ice and water shield. These materials serve different purposes in moisture protection and have distinct properties, installation methods, and costs. This article will provide an in-depth comparison of roofing felt versus ice and water shield to help homeowners and contractors make informed decisions.
| Feature | Roofing Felt | Ice and Water Shield |
|---|---|---|
| Material | Asphalt-saturated felt paper | Rubberized asphalt with a self-adhesive membrane |
| Water Resistance | Moderate; serves as secondary water barrier | High; forms a waterproof seal |
| Common Use | Under shingle layers over entire roof | Applied in vulnerable areas like eaves and valleys |
| Cost | More affordable | Higher cost due to advanced material properties |
| Installation | Requires nailing or stapling | Self-adhesive, peel-and-stick application |
What Is Roofing Felt?
Roofing felt, often called tar paper, is a traditional underlayment made primarily by saturating heavy paper or fiberglass mat with asphalt. It is available in various thicknesses, typically 15-pound or 30-pound felt, which refers to weight per 100 square feet. Roofing felt acts as a protective layer that sits beneath shingles, providing moderate water resistance and helping to protect the roof deck from moisture intrusion caused by wind-driven rain or ice dams.
Its flexibility and ease of installation have made it a common choice for decades. However, it is not fully waterproof and will absorb some moisture if left exposed for extended periods.
What Is Ice And Water Shield?
Ice and water shield is a revolutionary roofing underlayment designed to provide superior waterproofing. It is a self-adhesive membrane made from rubberized asphalt with a polyethylene top layer, allowing it to create a watertight seal over vulnerable decking areas. This underlayment is especially critical in regions prone to ice dams and severe weather.
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The material adheres directly to the roof deck and seals around nails and fasteners. Its waterproof nature makes it effective at preventing leaks caused by ice dams or wind-driven rain.
Key Differences Between Roofing Felt and Ice And Water Shield
1. Material Composition
Roofing felt is made from asphalt-saturated paper or fiberglass mats, which provides a breathable but water-resistant barrier. Ice and water shield uses an advanced rubberized asphalt formula with a sticky backing, which forms a permanent waterproof bond to the roof substrate.
2. Water Protection Capabilities
Roofing felt offers moderate moisture resistance but may allow water penetration if under prolonged exposure. Ice and water shield is designed to be completely waterproof, especially around roof edges, eaves, valleys, and penetrations, protecting these high-risk areas from leaks.
3. Installation Methods
Roofing felt is laid out in sheets and secured with nails or staples. It requires proper overlapping and fastener placement to maintain its effectiveness. Ice and water shield is peel-and-stick, simplifying installation and ensuring an air-tight seal that conforms closely to irregular surfaces.
4. Cost Differences
Roofing felt is significantly more affordable and frequently used as a full roof underlayment. Ice and water shield is more expensive but typically applied in specific zones rather than the entire roof, offsetting its higher price.
When to Use Roofing Felt
- For complete roof coverage to protect decking under standard shingles
- In areas with lower risk of ice dam formation
- For budget-conscious roofing projects wanting basic moisture resistance
- When a breathable underlayment is preferred for ventilation concerns
Roofing felt is best as a general underlayment providing secondary water resistance across the entire roof.
When to Use Ice and Water Shield
- On roof edges and eaves vulnerable to ice dams
- In valleys where water runoff concentrates
- Around chimneys, skylights, and roof penetrations
- In regions with harsh winters or heavy rainfall
- Where superior waterproofing is necessary to prevent leaks
Ice and water shield offers enhanced protection in critical areas prone to water infiltration.
Benefits and Drawbacks of Roofing Felt
| Benefits | Drawbacks |
|---|---|
| Cost-effective and widely available | Not fully waterproof; can absorb moisture |
| Easy to install and lightweight | Requires careful nailing; vulnerable to tearing |
| Provides a smooth layer for shingles to adhere | Less durable under prolonged UV exposure |
Benefits and Drawbacks of Ice and Water Shield
| Benefits | Drawbacks |
|---|---|
| High waterproofing capability; seals around nails | Higher material cost |
| Self-adhering, reducing installation errors | Can be difficult to reposition once applied |
| Effective in extreme weather and ice dam prevention | May require professional installation for best results |
Impact on Roofing Longevity and Home Protection
Using the right underlayment influences the roof’s ability to repel water and protect the home’s structural integrity. While roofing felt offers a baseline level of moisture protection to prevent minor leaks, ice and water shield provides a robust barrier against severe leaks caused by ice dams and water infiltration.
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Many modern roofing projects combine both materials—applying ice and water shield in key areas and roofing felt elsewhere—to balance cost, protection, and durability effectively.
Environmental and Climate Considerations
Climate plays a significant role in selecting an underlayment. In colder states experiencing ice damming, ice and water shield is often a necessity. In warmer, drier climates, basic roofing felt may suffice.
Irrigation drainage patterns, roof slope, and local building codes should also guide underlayment choice. Some codes mandate ice and water shield in vulnerable zones to minimize insurance risks and leakage.
Installation Tips for Best Performance
- Ensure roof decking is clean and dry before applying any underlayment.
- Overlap each roll properly to maintain waterproof layering.
- For ice and water shield, apply firmly and avoid wrinkles for a complete seal.
- Fasten roofing felt securely to prevent shifting during installation.
- Follow manufacturer guidelines for both materials, especially regarding temperature during application.
Cost Comparison: Budgeting for Roofing Felt and Ice and Water Shield
| Underlayment Type | Average Price Per Square (100 sq.ft.) | Installation Complexity |
|---|---|---|
| Roofing Felt | $15 – $40 | Simple DIY or contractor installation |
| Ice and Water Shield | $80 – $120 | Requires careful application; often professional |
Using ice and water shield selectively in high-risk areas is a cost-efficient approach.
Common Myths About Roofing Felt and Ice And Water Shield
- Myth: Roofing felt is waterproof. Fact: It resists moisture but is not a waterproof membrane.
- Myth: Ice and water shield can be used without roofing felt under shingles. Fact: Ice and water shield is typically applied only in critical areas, not the entire roof.
- Myth: Ice and water shield is difficult and time-consuming to install. Fact: Its peel-and-stick application facilitates easier installation if done with care.
Summary
Choosing between roofing felt and ice and water shield depends on the specific needs of the roofing project. Roofing felt is an economical, time-tested underlayment that provides basic moisture resistance. Ice and water shield offers superior waterproofing, ideal for vulnerable roof sections and harsh climates. Combining both is a modern best practice that balances protection and budget, ensuring roofs stand strong against water infiltration for years to come.