Home Roofing Everything You Need To Know About Underlayment For Roofing

Everything You Need To Know About Underlayment For Roofing

The roofing underlayment market has become a critical segment of the global construction industry. According to recent industry data, the roofing underlayment market was valued at approximately $22 billion by the end of 2023 and is projected to grow at a compound annual growth rate (CAGR) of 5.8%, reaching nearly $22.8 billion in 2024 . This rapid growth reflects a fundamental shift in how modern roofs are designed—not as a single layer of shingles or panels, but as an integrated system where underlayment plays a decisive role in durability, moisture control, and overall roof performance.

While most homeowners focus on visible roofing materials such as shingles, metal panels, or tiles, roofing professionals recognize that underlayment is the backbone of a reliable roofing system. When properly selected and installed, underlayment provides continuous protection against water intrusion, compensates for installation imperfections, and safeguards the roof structure during extreme weather events or unexpected material failures.

What Is Roofing Underlayment?

Roofing underlayment is a protective sheet or membrane installed directly over the roof deck (typically plywood or OSB) and beneath the final roofing material. Its primary function is to act as a secondary barrier against water, wind-driven rain, and moisture vapor.

Even the best roofing materials are not fully watertight on their own. Shingles can lift, tiles can crack, and metal panels can expand or contract. Underlayment ensures that if water bypasses the primary roofing surface, it does not reach the roof deck and interior structure.

In modern roofing systems, underlayment also contributes to:

Temporary weather protection during installation delays
Improved roof longevity
Code compliance and manufacturer warranty validation
Enhanced fire resistance and safety

Why Roofing Underlayment Is Essential in Modern Roofing Systems

Underlayment functions quietly beneath the roof covering, but its role is critical. A roof without proper underlayment is far more vulnerable to leaks, structural decay, and premature failure.

Moisture and Water Protection

Underlayment prevents water infiltration caused by wind-driven rain, ice dams, snow buildup, or minor roof damage. This is especially important at valleys, eaves, ridges, and roof penetrations.

Protection During Construction

Roof installations are not always completed in a single day. Underlayment provides temporary weather protection, preventing interior damage if rain occurs before the final roofing material is installed.

Structural Preservation

By keeping moisture away from the roof deck, underlayment prevents wood rot, mold growth, and delamination—issues that significantly weaken the roof structure over time.

Fire and Safety Benefits

Some underlayments carry Class A fire ratings, improving overall fire resistance. Slip-resistant surfaces also enhance worker safety during installation.

Types of Roofing Underlayment (Detailed Breakdown)

Roofing underlayments can be broadly divided into three primary categories, each designed for specific performance needs and environmental conditions.

Asphalt-Saturated Felt Underlayment

Often called felt paper or tar paper, asphalt-saturated felt is one of the oldest and most widely used underlayment materials.

Composition:
A base mat (organic or fiberglass) saturated with asphalt to provide water resistance.

Advantages:

Cost-effective and widely available
Familiar installation process
Suitable for basic asphalt shingle roofs in mild climates

Limitations:

Absorbs moisture rather than repelling it
Tears easily under foot traffic or high winds
Degrades faster under prolonged UV exposure

Felt underlayment is best suited for budget-conscious projects and regions with moderate, predictable weather conditions. It is increasingly being replaced by synthetic alternatives in modern construction.

Synthetic Roofing Underlayment

Synthetic underlayment represents a major advancement in roofing technology. It is manufactured using woven or spun polypropylene or polyethylene polymers engineered for strength and stability.

Advantages:

Extremely lightweight yet highly durable
Superior tear and puncture resistance
Resists mold, mildew, and moisture absorption
Longer UV exposure ratings during construction
Improved traction for installer safety

Limitations:

Higher upfront cost compared to felt

Synthetic underlayment is now the preferred choice for most professional roofing installations, particularly in regions with fluctuating weather, high winds, or extreme temperatures.

Rubberized Asphalt (Self-Adhering) Underlayment

Rubberized asphalt underlayment is considered the highest-performing underlayment option available.

Composition:
Asphalt combined with rubber polymers and a peel-and-stick adhesive backing.

Advantages:

Fully waterproof membrane
Self-seals around nails and fasteners
Exceptional performance in snow, ice, and heavy rainfall
Highly flexible in both hot and cold temperatures

Limitations:

Highest material cost
Heavier and more labor-intensive installation

This underlayment is commonly used in high-risk areas such as roof valleys, eaves, chimneys, skylights, and locations prone to ice dams.

Best Roofing Underlayment Products for 2024

Modern manufacturers offer advanced underlayments engineered for performance and ease of installation:

FeltBuster® Synthetic Roofing Felt by GAF: Lightweight, tear-resistant, moisture-repellent, and eligible for extended system warranties.
RoofRunner® by CertainTeed: High-strength synthetic underlayment with excellent weather resistance and easy handling.
Grace Ice & Water Shield® by GCP Applied Technologies: Premium self-adhering membrane ideal for leak-prone areas.
ProArmor® Synthetic Underlayment by Owens Corning: Durable, slip-resistant, and designed for extended exposure.
Tyvek® Protec™ 120 by DuPont: UV-resistant up to 90 days, Class A fire-rated, and designed for enhanced safety and moisture control.

How to Choose the Right Roofing Underlayment (In-Depth)

Climate and Weather Conditions

High rainfall, snow, coastal winds, or extreme heat require underlayments with superior waterproofing and durability.

Roof Design and Pitch

Steeper roofs shed water faster, while low-slope or complex roofs need higher-performing membranes to compensate for slower drainage.

Roofing Material Compatibility

Metal, tile, asphalt, cedar, and flat roofing systems all require different underlayment characteristics to perform correctly.

Budget vs Long-Term Performance

While felt underlayment costs less initially, synthetic and rubberized options often provide better value through longer service life and reduced maintenance.

Building Codes and Warranty Requirements

Many manufacturers require specific underlayment types to maintain warranty coverage. Local codes may also mandate ice-and-water protection in certain regions.

Recommended Underlayment by Roofing Type

Metal Roofing

Synthetic underlayment is ideal due to its resistance to heat, tearing, and moisture. It also accommodates thermal expansion and contraction of metal panels.

Asphalt Shingle Roofing

Felt remains common, but synthetic underlayment offers better durability, water resistance, and long-term reliability.

Flat Roofing Systems

Self-adhering membranes are essential due to limited drainage and higher risk of water pooling.

Cedar Shake Roofing

Synthetic underlayment allows breathability while preventing moisture absorption, reducing warping, mold, and decay.

Conclusion

Roofing underlayment is not an optional accessory—it is a critical structural component that determines how well a roof performs under stress, weather exposure, and time. Selecting the right underlayment strengthens the entire roofing system, protects against moisture-related failures, and significantly extends roof lifespan.

By carefully evaluating climate conditions, roof type, budget, and professional recommendations, homeowners can make informed decisions that ensure long-term protection and peace of mind. Whether installing a new roof or replacing an aging one, investing in high-quality roofing underlayment is one of the smartest choices you can make for the durability and resilience of your home.

Frequently Asked Questions (FAQs)

Why do you need furring strips under a metal roof?

Furring strips are recommended under metal roofing because they create an air gap between the roof deck and metal panels. This space improves airflow, reduces moisture buildup, and helps prevent condensation. Furring strips also provide a smoother, more secure surface for fastening panels and can improve insulation efficiency, helping regulate indoor temperatures and reduce energy costs.

Can I use Tyvek for roof underlayment?

Yes, Tyvek can be used as roof underlayment, specifically products like Tyvek® Protec™ 120. This type of underlayment acts as a moisture barrier installed beneath roofing materials such as asphalt shingles, metal panels, and cedar roofing. It helps protect the roof deck from water penetration while offering durability and slip resistance during installation.

Can I use roof underlayment as house wrap?

Although roof underlayment and house wrap both help resist moisture, they are designed for different purposes and should not be used interchangeably. Roof underlayment is built to withstand direct weather exposure and roofing loads, while house wrap is designed to allow wall assemblies to breathe. Using either material outside its intended application can lead to moisture trapping and long-term structural issues.

Can synthetic roof underlayment get wet?

Synthetic roof underlayment is water-resistant and can handle limited exposure to rain or snow. However, prolonged exposure to standing water or continuous moisture is not recommended. While modern synthetic underlayments do not absorb water like felt, the final roofing material should be installed as soon as possible to ensure maximum protection and performance.

Do I need tar paper under a metal roof?

Yes, installing tar paper or another approved underlayment beneath a metal roof is recommended to provide additional moisture protection. Underlayment helps prevent condensation, reduces noise, and protects the roof deck from water intrusion during harsh weather, ultimately extending the lifespan of the metal roofing system.

Is roof underlayment waterproof?

The waterproofing level of roof underlayment depends on the material. Asphalt-saturated felt provides temporary water resistance, while synthetic and rubberized asphalt underlayments offer significantly higher waterproofing performance. Synthetic underlayment is especially reliable in regions with frequent rain due to its moisture resistance and durability.