Roofing Material: Is Felt or Synthetic Underlayment Better?

Underlayment sits beneath the visible roofing material, so it is easy to forget about once a roof has been installed. However, this layer provides an important secondary barrier against moisture and helps protect the roof deck. When choosing between felt and synthetic underlayment, it is useful to understand how the two options differ.

What Is Felt Underlayment?

Traditional felt underlayment is made from a paper-based material saturated with asphalt. It has been used in roofing for many years and remains a common choice for certain applications.

Felt is generally affordable and familiar to roofing companies and professionals. It can provide effective protection when properly installed, but it may be more vulnerable to tearing, wrinkling, and moisture exposure during installation than many modern synthetic products.

What Is Synthetic Underlayment?

Synthetic underlayment is typically manufactured using polymers designed to provide greater durability and resistance to moisture. It is lightweight, generally easier to handle, and can offer greater resistance to tearing during installation.

Many synthetic products are also designed to remain exposed for a specified period while the roofing project is being completed. However, exposure limits vary by manufacturer, so installation guidelines should always be followed.

Which One Is Better?

There is no universal answer. Synthetic underlayment is often preferred for its durability, handling characteristics, and moisture resistance, particularly on larger or more complex roofing projects.

Felt may still make sense for certain applications where budget, roofing design, and local requirements are important considerations. The quality of installation matters regardless of which material is selected.

Installation Is Just as Important

Even the best underlayment cannot compensate for poor installation. Proper overlaps, fastening, sealing, and integration with flashing and roof penetrations are all essential.

The underlayment also needs to be compatible with the roofing material installed above it. Manufacturer instructions and applicable building requirements should guide the selection and installation process.

Consider the Entire Roofing System

At High Performance Roofing Corp, we look at underlayment as one part of the complete roofing system. The right choice depends on the roof design, materials, climate exposure, project requirements, and long-term goals of the property owner.

For many modern residential roofing projects, synthetic underlayment offers useful advantages. However, felt can still be an appropriate option in certain circumstances. Rather than choosing based solely on price, homeowners should consider the expected performance of the complete system and the quality of the installation.