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Best Underlayment For Asphalt Shingles: A Complete Guide
Table of Contents
- Introduction
- What Is Roof Underlayment?
- Why Underlayment Is Important for Asphalt Shingles
- Types of Roof Underlayment
- Asphalt-Saturated Felt
- Synthetic Underlayment
- Rubberized Asphalt
- Comparison Table of Underlayment Types
- Best Underlayment Products for Asphalt Shingles (2025)
- How to Choose the Best Underlayment for Your Roof
- Installation Tips and Best Practices
- Common Mistakes to Avoid
- FAQs About Roof Underlayment
- Conclusion
1. Introduction
When it comes to protecting your home, the roofing system plays a critical role. While asphalt shingles are the most visible and commonly discussed component, there’s an unsung hero beneath them: the underlayment. Choosing the best underlayment for asphalt shingles is vital for ensuring durability, weather protection, and long-term performance.
In this blog, we’ll walk you through the different types of underlayment, their pros and cons, product recommendations, installation tips, and how to choose the right one for your project.
2. What Is Roof Underlayment?
Roof underlayment is a water-resistant or waterproof barrier material that is installed directly onto the roof deck, beneath the asphalt shingles. Its primary function is to serve as a secondary protective layer in case water gets past the shingles.
Key Functions:
- Prevent water infiltration
- Protect against wind-driven rain
- Improve fire resistance
- Smooth the surface for shingle application
- Enhance roof lifespan
3. Why Underlayment Is Important for Asphalt Shingles
Even the best asphalt shingles are not completely waterproof. Tiny cracks, nail penetrations, or wind-driven rain can allow moisture to reach the roof deck. The underlayment acts as the last line of defense, preventing that moisture from seeping into your attic or insulation.
Key Benefits:
- Waterproofing: Protects roof deck from moisture and rot.
- Wind Protection: Secures your roofing system against wind-driven rain.
- Temperature Regulation: Helps insulate and stabilize attic temperatures.
- Improved Fire Rating: Some underlayments offer Class A fire resistance.
4. Types of Roof Underlayment
There are three main types of underlayment used with asphalt shingles. Each has specific benefits and ideal use cases.
4.1 Asphalt-Saturated Felt
Also known as felt paper or tar paper, this is the traditional choice.
- Material: Organic mat saturated with asphalt.
- Available Weights: 15 lb and 30 lb felt (30 lb is thicker and more durable).
Pros:
- Affordable
- Readily available
- Easy to install
Cons:
- Heavier
- Tears easily when wet
- Less durable than synthetics
4.2 Synthetic Underlayment
Made from polypropylene or polyethylene materials, synthetic underlayments are engineered for superior performance.
Pros:
- Lightweight and easy to carry
- Tear-resistant
- Slip-resistant surface
- Longer lifespan
- Better UV resistance
Cons:
- More expensive than felt
- Not all products are breathable (can trap moisture if not vented properly)
4.3 Rubberized Asphalt
Rubberized asphalt underlayment is a premium, self-adhering product with excellent waterproofing properties.
Pros:
- Completely waterproof
- Self-sealing around nails
- Ideal for valleys and eaves
- Best for ice and water shield
Cons:
- High cost
- Can be difficult to remove if repairs are needed
- May require a primer
5. Comparison Table of Underlayment Types
| Feature | Asphalt Felt | Synthetic Underlayment | Rubberized Asphalt |
|---|---|---|---|
| Water Resistance | Moderate | High | Excellent |
| Tear Resistance | Low | High | High |
| UV Protection | Low | Moderate to High | High |
| Lifespan | 5–10 years | 20–30 years | 30+ years |
| Cost | $ | $$ | $$$ |
| Installation Difficulty | Easy | Easy | Moderate to Hard |
| Fire Resistance | Moderate | High | High |
6. Best Underlayment Products for Asphalt Shingles (2025)
Here are some of the top-rated underlayments currently on the market:
6.1 GAF FeltBuster® Synthetic Roofing Felt
- Type: Synthetic
- Key Feature: Non-asphaltic, non-woven polypropylene
- Benefits: Light, strong, slip-resistant, budget-friendly
6.2 Owens Corning ProArmor® Synthetic
- Type: Synthetic
- Key Feature: Enhanced UV resistance (up to 90 days exposure)
- Benefits: Durable, lightweight, good grip, compatible with most shingles
6.3 Grace Ice & Water Shield®
- Type: Rubberized Asphalt
- Key Feature: Self-adhering membrane
- Benefits: Exceptional leak protection in critical areas like valleys and edges
6.4 CertainTeed RoofRunner™
- Type: Synthetic
- Key Feature: 6-month UV exposure rating
- Benefits: Long installation window, lightweight, easy chalk line visibility
6.5 Titanium® UDL30
- Type: Premium Synthetic
- Key Feature: Designed for all slopes, class A fire rating
- Benefits: Advanced moisture barrier, ideal for steep-slope roofing
7. How to Choose the Best Underlayment for Your Roof
Consider Your Climate
- Wet climates: Choose waterproof or rubberized asphalt.
- Hot climates: Use UV-resistant synthetic products.
- Cold climates: Prioritize ice and water shield for eaves and valleys.
Roof Slope
- Low slope (<4:12): Use rubberized asphalt or dual-layered synthetic underlayment.
- Steep slope: Synthetic underlayments provide better traction and installation ease.
Budget
- Tight budget: Use felt or basic synthetic.
- Mid-range: Choose high-performance synthetic.
- Premium: Go with rubberized asphalt for full-coverage or in vulnerable areas.
Roofing Code Requirements
Always check local building codes for underlayment specifications and fire rating requirements.
8. Installation Tips and Best Practices
- Always start from the bottom edge of the roof and work upward.
- Overlap layers by at least 2 inches horizontally and 4 inches vertically.
- Nail or staple according to the manufacturer’s recommendations.
- Use cap nails or plastic cap staples for synthetic products.
- Avoid installing underlayment in wet or windy conditions.
- Use primer where required for rubberized asphalt.
- Install ice and water shield at all eaves, valleys, and penetrations (vents, chimneys).
9. Common Mistakes to Avoid
- Skipping underlayment: Never install shingles directly on the roof deck.
- Improper overlaps: Inadequate laps can allow water infiltration.
- Wrong product choice: Using felt in high-moisture or high-heat areas can lead to failure.
- Overexposing: Some underlayments can only be exposed for a limited time before roofing must be completed.
- Poor fastening: Incorrect nailing can cause tearing and water leaks.
10. FAQs About Roof Underlayment
Q1: Do I really need underlayment under asphalt shingles?
Yes. Building codes typically require it, and it provides critical protection against water damage.
Q2: Can I use synthetic underlayment for an entire roof?
Yes. In fact, many pros recommend it for full coverage due to its durability and ease of installation.
Q3: Is rubberized asphalt underlayment worth the cost?
If you live in a region with harsh weather, ice dams, or frequent storms, it’s absolutely worth the investment—especially in vulnerable areas.
Q4: How long does underlayment last?
- Felt: 5–10 years
- Synthetic: 20–30 years
- Rubberized: 30+ years (if properly installed)
Q5: What happens if I install shingles without underlayment?
You’re risking serious water damage, mold, and roof deck rot. It can also void warranties and violate code.
11. Conclusion
The underlayment you choose can make or break your roofing system. While it’s hidden beneath the shingles, its performance is crucial for weather protection, energy efficiency, and longevity. Whether you opt for traditional felt, modern synthetic, or advanced rubberized asphalt, always choose based on your climate, budget, and roof design.
Need help choosing the best underlayment for your specific needs? Talk to a certified roofing contractor or check with local building codes to make the most informed decision.
