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Roof Underlayment Options: Choosing the Right Barrier for Phoenix’s Extreme Temperature Swings

When Phoenix’s Scorching Heat Meets Your Roof: Choosing the Right Underlayment Barrier for Arizona’s Extreme Temperature Swings

Phoenix homeowners face a unique roofing challenge that few other cities in America experience. With average high temperatures in summer being the hottest of any major city in the United States, there are 111 days annually with a high of at least 100°F, and highs top 110°F an average of 21 days during the year. On June 26, 1990, the temperature reached an all-time recorded high of 122°F. These extreme conditions create serious stress on roofing systems, making the choice of proper underlayment absolutely critical for long-term protection.

Understanding the Heat Challenge

High temperatures create a high amount of stress on the roofing underlayment because the heat essentially has nowhere to go, driving up the surface temperature of the roof. When roofs approach daytime temperatures of nearly 200°F, standard underlayment materials can fail catastrophically. If the roof becomes too hot, the adhesive used in self-adhered roofing underlayment may soften, resulting in sticky adhesive dripping onto the exterior of the building or finding its way into gaps in the roof sheathing.

For Phoenix homeowners, this isn’t just a theoretical concern—it’s a daily reality during the summer months when the daily normal low remains at or above 80°F for an average of 74 days per summer, and Phoenix set its record for the warmest daily low temperature at 97°F on July 19, 2023.

High-Temperature Underlayment Options

Traditional felt underlayment, while cost-effective, faces significant challenges in Phoenix’s climate. Traditional felt roofing underlayment generally can’t be left exposed for more than a few hours, as the material may dry out or leach oils in the heat, impacting the felt’s ability to protect against moisture. However, for Phoenix’s specific conditions, several specialized options perform better:

Modified Bitumen High-Temperature Underlayment

High Temperature Roof Underlayment is a self-adhered rubberized waterproof roofing membrane underlayment with a service temperature up to 260°F. Products like Weather-Armor HT³ are specifically designed to resist heat up to 265°F, with ingredients that optimize performance in hot climates and under high heat conditions. High-temperature resistant membranes allow for exposure to heat up to 260°F.

Synthetic Underlayment Considerations

While synthetic underlayment offers many advantages, Phoenix presents a unique challenge. Even high-dollar roofers in Arizona are wary of using synthetic underlayment, offering felt options instead and pushing back on synthetic even if it costs more, because synthetic does not hold up in the dry heat and degrades too quickly. Most synthetic underlayment is highly resistant to UV rays, which makes them ideal for Arizona’s intense summers where the UV index reaches double digits. However, synthetics are not recommended under tile at all for Arizona, as they are best for under shingle roofs in cold climates.

Liquid-Applied Underlayment

Liquid-applied underlayments are designed to withstand very high temperatures, often up to around 300°F, making them an excellent choice for areas subjected to intense solar heat or under metal roofs.

Climate-Specific Recommendations for Phoenix

Phoenix’s desert climate requires a different approach than other regions. Arizona is hot and dry like a convection oven. For this weather, felt underlayment works well because it’s cheaper than synthetic and is water-resistant but not waterproof—you don’t need waterproof underlayment in Arizona since there’s no worry about water from melting ice dams.

Double-layer installation is common practice in Arizona, with the best roofers recommending an underlayment of two layers of 40-pound felt as well as modified bitumen roofing in valleys. Two layers of ASTM 30-pound asphalt-impregnated felt should last 20 to 30 years, with two-layer installations often having twice the warranty period of single-layer installations.

Professional Installation Matters

Choosing the right material is only half the battle—proper installation is crucial. All components used to produce the underlayment must be tested to ensure they will withstand a metal roof’s high-temperature environment (240°F to 265°F). When selecting a roofing company phoenix homeowners trust, it’s essential to work with contractors who understand these extreme temperature challenges.

Roofing All Stars LLC is a market leader in roofing and building services, with a local history serving Phoenix, AZ and the surrounding areas as a full-service residential roofing contractor serving Phoenix, Chandler, Gilbert and the surrounding areas. Their commitment to honest, reliable, quality service means homeowners can expect the highest quality of workmanship and expertise, with their commitment to perform at the highest level of professionalism, safety and workmanship necessary to assure quality outcomes that stand the test of time.

Making the Right Choice

For Phoenix homeowners, the key considerations when selecting roof underlayment include:

Installing Class A fire-rated asphalt shingles and impact-resistant composite materials built for Arizona’s extreme weather conditions requires underlayment that can handle the unique challenges of the Sonoran Desert. Whether you choose high-temperature modified bitumen, carefully selected synthetic materials, or traditional felt in double layers, the key is working with experienced professionals who understand Phoenix’s extreme temperature swings and can recommend the best solution for your specific roof and budget.

Don’t let Phoenix’s punishing heat compromise your home’s protection. The right underlayment choice today will provide decades of reliable performance, even when temperatures soar well above 110°F during those long Arizona summers.