Roofing Felt vs Ice and Water Shield: Choosing the Best Protection for Your Roof

When it comes to roofing protection, homeowners and contractors often weigh the benefits of roofing felt versus ice and water shield. Both materials serve as underlayments beneath shingles, but their functions, application methods, and effectiveness differ significantly. Understanding these differences is crucial for making informed decisions about roof durability, especially in regions prone to extreme weather.

What Is Roofing Felt?

Roofing felt, often referred to as tar paper, is a traditional roofing underlayment made by saturating a base material like burlap or fiberglass with asphalt. It provides a water-resistant layer that protects the roof deck from sudden weather changes during construction or shingle failure. Felt underlayment comes in different weights, commonly 15-pound and 30-pound varieties, indicating its thickness and durability.

Felt serves as the first line of defense against moisture infiltration beneath roof shingles and helps prevent minor leaks from causing damage to wood decking. Its breathable nature allows for some vapor release, preventing moisture buildup under the roofing materials.

What Is Ice and Water Shield?

Ice and water shield is a peel-and-stick underlayment made from rubberized asphalt with a sticky adhesive backing. It forms a self-sealing, waterproof membrane that bonds directly to the roof deck, creating an impermeable barrier against ice dams, wind-driven rain, and blown snow. This material is highly effective in critical roof areas where leaks are most common, such as around valleys, eaves, chimneys, skylights, and roof penetrations.

The impermeable nature of ice and water shield prevents moisture from seeping into the decking, providing superior protection in cold or wet climates where ice dams form and lead to water infiltration.

Key Differences Between Roofing Felt and Ice and Water Shield

When To Use Roofing Felt

Roofing felt is ideal for full roof coverage as a basic underlayment beneath asphalt shingles, wood shakes, or metal roofing panels. It provides a suitable water-resistant layer that mitigates leak risk during installation and adds an extra moisture barrier. Felt is also a cost-effective solution for roofs in regions with less severe weather or where additional waterproofing is not mandatory by building codes.

Common scenarios for roofing felt use include residential homes in temperate climates and reroofing projects where budget constraints exist but basic protection is still needed.

When To Use Ice and Water Shield

Ice and water shield is essential in vulnerable roof areas prone to ice dams, heavy rain, and severe weather. Its application is critical along eaves, valleys, rakes, around chimneys, skylights, and vents where water intrusion is most likely. Many building codes recommend or require ice and water shield in these zones for enhanced waterproofing.

Homes in northern states, mountainous regions, or places with frequent freeze-thaw cycles benefit most from this membrane due to its self-sealing and waterproof capabilities, which significantly reduce roof leak risks.

Cost Considerations and Budgeting

Roofing felt generally costs between $0.15 and $0.50 per square foot, making it an affordable underlayment choice for standard roofing projects. Ice and water shield, on the other hand, ranges from $1.50 to $3.50 per square foot depending on the brand, thickness, and coverage area. Though more expensive, its durability and protection justify the investment in critical roof zones.

Many homeowners opt for a hybrid approach, combining roofing felt for overall coverage with ice and water shield in key vulnerable areas to balance cost and protection.

Installation Best Practices

Installing Roofing Felt

• Start at the bottom edge of the roof and roll felt horizontally across the deck.
• Overlap each row by 2 to 4 inches to ensure water shedding.
• Secure the felt with roofing nails or staples to prevent wind uplift.
• Avoid wrinkles or folds that could trap moisture.

Installing Ice and Water Shield

• Clean and dry the roof deck before application for proper adhesion.
• Start at eaves and valleys, pressing firmly to avoid air bubbles.
• Seal overlaps following manufacturer guidelines to maintain waterproof integrity.
• Apply around penetrations and edges carefully for maximum protection.

Longevity and Maintenance

Roofing felt generally lasts the lifespan of roofing shingles** under normal conditions but can degrade if exposed to prolonged sunlight or moisture during installation. It rarely acts as a long-term moisture barrier but is crucial during construction and minor leak prevention.

Ice and water shield, by contrast, offers long-term waterproofing durability due to its rubberized properties. It maintains elasticity and adhesion over time even with temperature fluctuations, serving as a robust defense layer throughout the roof’s lifespan.

Environmental and Safety Considerations

Roofing felt is made from organic or fiberglass materials saturated with asphalt, which presents limited environmental impact but can release volatile organic compounds (VOCs) during installation. Disposal requires care due to the asphalt content.

Ice and water shield also contains asphalt and polymers, but its production involves synthetic materials and adhesives. While more effective, it is less biodegradable, so recycling options are limited. Using genuine products from responsible manufacturers ensures better environmental compliance.

Summary Table: Roofing Felt vs Ice and Water Shield Comparison