Synthetic vs Felt Roof Underlayment: Which Is Right for Your Roofing System?
What Is Roof Underlayment?
Roof underlayment is a protective layer installed between the roof deck and the final roofing material. Its primary role is to act as a secondary barrier against water intrusion, helping protect the structure from wind-driven rain, moisture, and temporary exposure during construction. Choosing the right type of roof underlayment has a direct impact on roof durability, code compliance, and long-term performance.
Two of the most common options used today are synthetic roof underlayment and traditional felt underlayment. While both serve the same basic purpose, their performance characteristics and suitability for modern construction are very different.
What Is Felt Roof Underlayment?
Felt roof underlayment, sometimes referred to as asphalt-saturated felt, has been used in roofing systems for decades. It is typically made from a fiberglass or organic mat saturated with asphalt to provide basic water resistance.
Characteristics of Felt Underlayment
- Provides basic moisture protection
- Typically available in 15 lb or 30 lb weights
- Lower upfront material cost
- Familiar installation method
While felt underlayment has a long history, it has several limitations that can impact roof performance in demanding conditions.
Limitations of Felt Underlayment
- Can absorb moisture and lose strength when wet
- Prone to wrinkling, tearing, and degradation
- Heavier and more difficult to handle
- Limited exposure ratings
For these reasons, felt underlayment is becoming less common in high-performance and code-driven roofing projects.
What Is Synthetic Roof Underlayment?
Synthetic roof underlayment is engineered from advanced polymer materials designed to outperform traditional felt. These underlayments are manufactured to provide consistent performance, improved durability, and better resistance to environmental stresses.
Key Features of Synthetic Roof Underlayment
- High tensile and tear strength
- Excellent water resistance
- Lightweight and easy to install
- Enhanced slip resistance for jobsite safety
- Longer allowable exposure times
Synthetic roof underlayment has become the preferred choice for most modern residential and commercial roofing systems.
Synthetic vs Felt Roof Underlayment: Key Differences
Durability and Strength
Synthetic roof underlayment offers significantly higher tear resistance than felt, allowing it to withstand foot traffic, wind uplift, and installation stresses without damage. Felt underlayment is more likely to tear or wrinkle, especially when wet.
Moisture Resistance
Unlike felt, synthetic underlayment does not absorb moisture. This helps maintain consistent performance even during extended exposure to rain or humidity during construction.
Installation and Jobsite Safety
Synthetic underlayment is lightweight and often features textured or slip-resistant surfaces, improving handling and safety. Felt underlayment can become slippery and difficult to manage when wet.
Exposure Ratings
Many synthetic roof underlayment products offer extended exposure ratings, allowing roofing work to proceed without compromising protection. Felt underlayment typically has limited exposure tolerance.
Long-Term Performance
Synthetic materials maintain their integrity over time, while felt can degrade, shrink, or lose effectiveness under prolonged environmental stress.
Comparison Table: Synthetic vs Felt Roof Underlayment
| Feature | Synthetic Roof Underlayment | Felt Roof Underlayment |
|---|---|---|
| Material | Engineered polymers | Asphalt-saturated mat |
| Tear Resistance | High | Low to Moderate |
| Water Absorption | Does not absorb water | Can absorb moisture |
| Weight | Lightweight | Heavier |
| Exposure Rating | Extended | Limited |
| Jobsite Safety | Slip-resistant options | Can be slippery |
| Durability | Long-term performance | Prone to degradation |
Code Requirements and Modern Roofing Standards
Building codes increasingly emphasize performance, durability, and moisture control. In many regions, especially high-wind or coastal areas, synthetic roof underlayment is often specified to meet testing and approval requirements.
Using code-approved synthetic underlayment can help simplify inspections, reduce project risk, and support long-term roof performance. While felt underlayment may still be permitted in some applications, it may not meet the expectations of modern building standards.
When Felt Roof Underlayment May Be Used
In limited cases, felt underlayment may still be used for:
- Temporary or low-budget projects
- Repairs or reroofing where permitted by code
- Situations where exposure time is minimal
However, even in these scenarios, contractors often choose synthetic alternatives for improved reliability and ease of installation.
Why Synthetic Roof Underlayment Is the Preferred Choice
For most residential and commercial roofing projects, synthetic roof underlayment provides superior performance across every key category. Its durability, moisture resistance, and consistency make it a reliable solution for modern roofing systems.
Contractors, builders, and specifiers increasingly select synthetic roof underlayment to reduce callbacks, improve installation efficiency, and meet evolving code requirements.
Ark Guard Roofing Underlayment Solutions
Ark Guard manufactures high-performance synthetic roofing underlayment solutions engineered for durability, water resistance, and code compliance.
- Arcno – Lightweight synthetic underlayment designed for strength and stability
- Armour – Durable synthetic underlayment for residential and commercial roofing
- Armour AD Pro – Self-adhered underlayment for enhanced protection in critical roof areas
Each Ark Guard roofing underlayment product is designed to integrate seamlessly into modern roofing systems.
FAQs: Synthetic vs Felt Roof Underlayment
Is synthetic roof underlayment better than felt?
Yes. Synthetic roof underlayment offers superior durability, moisture resistance, and long-term performance compared to traditional felt underlayment.
Is felt roof underlayment still allowed by code?
Felt underlayment may still be permitted in some jurisdictions, but code requirements vary by region. Always verify local building code requirements.
Does synthetic underlayment cost more?
Synthetic underlayment typically has a higher upfront cost, but it often reduces labor time, installation issues, and long-term maintenance costs.
Can synthetic roof underlayment be used under all roof types?
Yes. Synthetic roof underlayment is commonly used beneath shingles, metal roofing, and tile systems.
Choosing the Right Roof Underlayment
Selecting the right roof underlayment depends on performance requirements, climate conditions, and code compliance needs. For modern construction, synthetic roof underlayment provides the reliability and protection required to support high-performance roofing systems.