Synthetic Underlayment or Felt Paper Which is the Best Choice for Your Roofing Project

Choosing the right underlayment for your roofing project can make a big difference in the durability and protection of your roof. Two common options are synthetic underlayment and felt paper. Both serve as a protective layer beneath roofing materials, but they have distinct characteristics that affect performance, cost, and installation. This post breaks down the differences to help you decide which option fits your needs.

What Is Roofing Underlayment and Why It Matters

Roofing underlayment is a layer installed between the roof deck and the shingles or other roofing materials. Its main job is to provide a secondary barrier against water infiltration, wind, and other elements. It also helps protect the roof deck during installation before the outer roofing is in place.

Without proper underlayment, moisture can seep into the roof structure, causing damage like rot, mold, and leaks. Choosing the right underlayment improves the roof’s lifespan and can prevent costly repairs.

Felt Paper: The Traditional Choice

Felt paper, also called tar paper, has been used for decades as roofing underlayment. It is made from organic or fiberglass materials saturated with asphalt to make it water-resistant.

Advantages of Felt Paper

• Cost-effective: Felt paper is generally less expensive than synthetic underlayment, making it a budget-friendly option.

• Availability: It is widely available and familiar to most roofing contractors.

• Easy to install: Felt paper is relatively simple to roll out and nail down.

  
  

Limitations of Felt Paper

• Durability: Felt paper can tear easily, especially in windy conditions or during installation.

• Water resistance: While it resists water, it is not waterproof. Prolonged exposure to moisture can degrade felt paper.

• Weight: Felt paper is heavier than synthetic options, which can make handling more difficult.

• Shorter lifespan: Felt paper tends to break down faster over time, especially under harsh weather.

  
  

Synthetic Underlayment: The Modern Alternative

Synthetic underlayment is made from woven or non-woven polypropylene or polyester materials. It is designed to be stronger and more water-resistant than felt paper.

Advantages of Synthetic Underlayment

• Superior durability: Synthetic underlayment resists tearing and punctures better than felt paper, even in strong winds.

• Waterproof qualities: Many synthetic options offer waterproof or highly water-resistant properties, providing better protection.

• Lightweight: Easier to handle and install due to its lighter weight.

• Longer lifespan: Synthetic materials hold up better over time, especially in extreme weather conditions.

• Slip resistance: Some synthetic underlayments have textured surfaces that improve safety for installers.

  
  

Potential Drawbacks of Synthetic Underlayment

• Higher cost: Synthetic underlayment usually costs more upfront than felt paper.

• UV sensitivity: Some synthetic products degrade if exposed to sunlight for extended periods, so timely installation of roofing materials is important.

• Compatibility: Not all synthetic underlayments work with every roofing system, so checking manufacturer recommendations is necessary.

  
  

Comparing Performance in Different Conditions

Weather Resistance

Synthetic underlayment generally outperforms felt paper in resisting water and wind. For example, in regions with heavy rain or snow, synthetic underlayment reduces the risk of leaks during storms. Felt paper may absorb moisture and lose effectiveness if exposed for too long.

Installation and Handling

Felt paper can be more prone to tearing during installation, especially in windy conditions. Synthetic underlayment’s strength and lighter weight make it easier and safer to install, reducing labor time and potential damage.

Cost Considerations

While felt paper is cheaper initially, synthetic underlayment’s durability can save money in the long run by reducing repairs and extending roof life. For homeowners planning to stay in their home for many years, investing in synthetic underlayment may be more cost-effective.

Environmental Impact

Some synthetic underlayments are recyclable and made from materials with lower environmental footprints compared to traditional felt paper, which often contains asphalt and organic fibers.

When to Choose Felt Paper

• You have a tight budget and need a low-cost underlayment.

• The roofing project is in a mild climate with less exposure to extreme weather.

• The roof will be covered quickly after installation, minimizing felt paper exposure.

• You prefer a traditional material that contractors are familiar with.

  
  

When to Choose Synthetic Underlayment

• You want a stronger, more durable underlayment that resists tearing.

• The roof is in an area prone to heavy rain, snow, or high winds.

• You want better water resistance and longer-lasting protection.

• Safety during installation is a priority due to slip-resistant surfaces.

• You are willing to invest more upfront for long-term benefits.

  
  

Practical Tips for Choosing and Installing Underlayment

• Check local building codes: Some areas require specific types of underlayment for certain roofing materials.

• Consult your roofing contractor: Experienced professionals can recommend the best underlayment based on your roof design and climate.

• Consider warranty coverage: Some roofing manufacturers require synthetic underlayment to maintain warranty validity.

• Install carefully: Proper installation is crucial regardless of material. Overlapping seams and securing edges prevent leaks.

• Plan timing: Avoid leaving underlayment exposed to sunlight for long periods, especially synthetic types sensitive to UV rays.

  
  

Final Thoughts on Synthetic Underlayment vs. Felt Paper

Both synthetic underlayment and felt paper have roles in roofing projects, but synthetic underlayment offers clear advantages in strength, water resistance, and longevity. It suits homeowners looking for durable protection and willing to invest a bit more upfront. Felt paper remains a viable option for budget-conscious projects in mild climates or where quick roof covering is possible.