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Best Roof Underlayment For Shingles: Complete Homeowner’s Guide
When planning a roof replacement or new installation, one of the most important choices you’ll make is selecting the best roof underlayment for shingles. While shingles are the visible outer layer of protection, the underlayment is the hidden defense that keeps your home safe from water infiltration, ice dams, and weather damage. Many homeowners focus heavily on shingle type but overlook underlayment, which plays a critical role in roof performance and lifespan.
This guide explains everything you need to know about roof underlayment—types, benefits, installation practices, and tips for making the right choice for your home. By the end, you’ll have the knowledge to confidently decide which underlayment will best serve your roofing system.
What Is Roof Underlayment?
Roof underlayment is a protective layer installed directly on top of the roof deck and beneath shingles. It serves as a secondary moisture barrier, shielding the decking from rain, snow, and ice that might get past the shingles.
Without underlayment, even a small shingle failure could lead to water reaching the wood decking, causing rot, mold, and structural damage. It’s a silent hero in the roofing system that ensures long-term durability.
Why Underlayment Matters
Many homeowners assume shingles alone are enough, but underlayment is critical for several reasons:
- Moisture Protection – Stops water intrusion when shingles are lifted by wind or damaged.
- Extra Defense During Installation – If shingles aren’t immediately installed, underlayment temporarily shields the decking.
- Uniform Surface for Shingles – Prevents uneven wood decking from affecting shingle appearance and fit.
- Ice and Water Barrier Support – Works alongside specialized products to prevent ice dam leaks.
- Fire Resistance – Some underlayments provide added fire protection, depending on material.
Types of Roof Underlayment
There are three primary types of underlayment used under shingles. Each has its pros and cons, making it important to understand the differences before choosing.
1. Asphalt-Saturated Felt (Felt Paper)
Traditionally known as tar paper, this has been used for decades.
- Pros:
- Affordable and widely available.
- Provides a moisture barrier.
- Easy to install.
- Cons:
- Less durable than synthetic options.
- Tears easily in high winds.
- Heavy and can wrinkle when wet.
It comes in two thicknesses: 15-pound felt (lighter, cheaper) and 30-pound felt (thicker, stronger, more water-resistant).
2. Synthetic Underlayment
A modern upgrade, synthetic underlayment is made from polypropylene or polyethylene.
- Pros:
- Lightweight yet strong.
- Resistant to tearing and UV damage.
- Provides superior water resistance.
- Safer walking surface for roofers.
- Cons:
- Higher cost than felt.
- Quality varies by brand.
This is quickly becoming the most popular choice due to its durability and reliability.
3. Rubberized Asphalt Underlayment
A premium product that offers maximum waterproofing.
- Pros:
- Self-sealing around nails.
- Excellent protection against ice dams and water infiltration.
- Highly durable and long-lasting.
- Cons:
- More expensive.
- Heavier and harder to install.
This type is often used in high-risk areas like valleys, roof edges, and around chimneys, though some homeowners opt for full-roof coverage.
Comparing the Best Roof Underlayments for Shingles
| Feature | Asphalt Felt | Synthetic Underlayment | Rubberized Asphalt |
|---|---|---|---|
| Cost | Low | Moderate | High |
| Durability | Fair | High | Very High |
| Water Resistance | Moderate | High | Excellent |
| UV Resistance | Low | Moderate–High | High |
| Installation Ease | Easy but heavy | Very Easy | Moderate |
| Nail Seal Protection | None | Minimal | Excellent |
How to Choose the Best Roof Underlayment for Shingles
Several factors should influence your decision:
- Climate
- Cold climates with heavy snow: Rubberized asphalt is ideal.
- Hot, sunny areas: Synthetic underlayment resists UV and heat better.
- Mild climates: Felt may still suffice as a budget option.
- Roof Pitch
- Low slopes benefit from stronger waterproofing like rubberized asphalt.
- Steeper slopes can use synthetic or felt effectively.
- Budget
- Felt is cheapest, synthetic is mid-range, rubberized asphalt is premium.
- Shingle Warranty Requirements
- Some manufacturers require specific underlayments for warranty validation.
Installation Process
Installing underlayment involves careful preparation and layering:
- Deck Preparation – Roof decking must be clean, dry, and smooth.
- Roll Out Underlayment – Begin at the bottom edge and work upward.
- Overlap Layers – Each row overlaps the one below for water-shedding.
- Fastening – Nails or staples secure underlayment, though self-adhesive versions bond directly.
- Detailing – Extra care is taken around valleys, chimneys, vents, and skylights.
Common Mistakes to Avoid
- Skipping underlayment altogether.
- Using lightweight felt in high-wind zones.
- Not overlapping properly, leaving gaps.
- Exposing non-UV resistant underlayment for too long before shingles are installed.
Benefits of Choosing the Right Underlayment
- Longer roof lifespan.
- Reduced risk of water damage.
- Improved energy efficiency in some cases.
- Peace of mind knowing there’s a backup defense beneath shingles.
The Evolution of Underlayment
Historically, roofs only used felt paper, but as roofing technology advanced, synthetic and rubberized asphalt emerged to solve felt’s weaknesses. Many professional roofers now consider synthetic underlayment the standard, while premium homes in harsh climates often rely on rubberized asphalt for complete security.
Cost Considerations
- Felt underlayment: $0.10–$0.50 per square foot.
- Synthetic underlayment: $0.20–$0.80 per square foot.
- Rubberized asphalt: $0.75–$1.50 per square foot.
While felt is cheapest, many homeowners see synthetic or rubberized as an investment in long-term protection.
Building Codes and Underlayment Requirements
In many regions, building codes specify underlayment requirements for residential roofing. This often includes:
- Ice barrier along eaves in cold climates.
- Minimum underlayment coverage for different roof pitches.
- Fire-rated underlayment in some areas.
Always check your local codes before starting a roofing project.
Myths About Roof Underlayment
Myth 1: Shingles alone are waterproof.
- False. Shingles shed water but don’t seal against leaks.
Myth 2: Underlayment isn’t needed on steep roofs.
- Incorrect. Water can still blow under shingles during storms.
Myth 3: Synthetic underlayment is too expensive.
- While pricier than felt, its long life and durability often make it more cost-effective.
Long-Term Impact on Home Value
A well-installed underlayment increases roof longevity, lowers maintenance costs, and enhances property value. Buyers often ask about the roof’s age and materials, and having high-quality underlayment is an invisible selling point that reassures them.
Case Example
A homeowner in a snowy northern state replaced their roof with felt underlayment. After a few winters, ice dams caused leaks, and repairs were needed. During the second roof replacement, they chose rubberized asphalt underlayment. Years later, despite severe winters, no leaks occurred—showing the difference the right underlayment makes.
Pros and Cons of Each Option
Felt Underlayment
- ✅ Affordable
- ✅ Easy to install
- ❌ Tears easily
- ❌ Poor long-term durability
Synthetic Underlayment
- ✅ Strong, lightweight, tear-resistant
- ✅ Better UV resistance
- ❌ More expensive than felt
Rubberized Asphalt
- ✅ Self-sealing, maximum waterproofing
- ✅ Best choice for harsh climates
- ❌ High cost
- ❌ More labor-intensive installation
Maintenance and Inspection
Though underlayment is hidden, you can indirectly protect it through:
- Keeping shingles in good condition.
- Ensuring proper attic ventilation.
- Clearing gutters to avoid water backup.
- Scheduling regular roof inspections.
If shingles fail, the underlayment is the last defense, so maintaining the outer layer is key.
Future Trends in Roof Underlayment
Manufacturers continue to improve products with eco-friendly materials, enhanced UV protection, and better adhesion. In some areas, synthetic underlayment is expected to fully replace felt due to performance advantages.
Checklist for Choosing the Best Underlayment
- Consider climate and weather risks.
- Review roof pitch.
- Balance budget and long-term protection.
- Check building code and warranty requirements.
- Consult with a professional roofer for recommendations.
Conclusion
Choosing the best roof underlayment for shingles is just as important as selecting the shingles themselves. While felt, synthetic, and rubberized asphalt all serve as protective barriers, each suits different needs and budgets. Felt is affordable but less durable, synthetic strikes a balance between cost and performance, and rubberized asphalt offers the highest level of protection for demanding climates.
Investing in the right underlayment means greater protection, longer roof life, and fewer costly repairs. Whether you’re building a new home or replacing an old roof, underlayment is the foundation of a roofing system you can trust. 440-235-3124
