Blog O Atlas Roofing Releases Guide to Essential Roof Underlayment

Beneath the vibrant colors and elegant designs of roof shingles lies a critical yet often overlooked component—the waterproofing underlayment. While homeowners admire the aesthetic appeal of their roofs, experienced contractors know that this hidden layer serves as the first line of defense against leaks and moisture damage.

Even seasoned professionals may not be fully versed in all types of underlayment materials. To help both contractors and homeowners make informed decisions, here’s a detailed breakdown of four primary types of roof underlayment and their applications.

Asphalt-saturated felt, a traditional and cost-effective option, consists of an organic mat (typically made from wood pulp cellulose fibers) impregnated with asphalt. This material is easy to install, provides a stable base for roofing materials, and effectively blocks moisture from penetrating the roof structure.

Asphalt, a complex hydrocarbon mixture, offers unique viscoelastic properties—balancing fluidity and elasticity under stress. When combined with the physical characteristics of organic felt, it forms a durable moisture barrier that ensures watertight protection for the roof deck.

• Gorilla Guard® 30 Engineered Felt: A high-performance underlayment enhanced with specialized additives and fiberglass, offering superior durability and efficiency compared to traditional asphalt felt.
• #15 Asphalt-Saturated Felt: Ideal for most standard-slope roofs, this product features high-density organic felt with excellent tear resistance.
• #30 Asphalt-Saturated Felt: Thicker and sturdier than standard options, providing enhanced tear resistance and a safer footing for workers on steep roofs.

For those seeking advanced solutions, synthetic underlayment—made from polypropylene and woven polymer grids—delivers lightweight yet robust performance. These materials are designed for longevity and ease of installation.

• Summit® 60 Synthetic Underlayment: Designed for steep-slope roofs, this woven grid underlayment offers 60 days of UV exposure resistance and resists moisture and mold growth.
• Summit® 180 Synthetic Underlayment: Similar to Summit 60 but with an extended 180-day UV exposure window, making it ideal for projects with longer timelines.

Self-adhered underlayment features a built-in adhesive layer, ensuring a strong bond to the roof deck. This type is particularly effective for asphalt shingles, metal roofs, and tile roofs, providing a stable base even in high winds or extreme weather.

• WeatherMaster® Ice & Water 200: An SBS-modified asphalt membrane offering extra protection against ice dams and wind-driven rain.
• WeatherMaster® Pro-Grade Ice & Water: A primary underlayment for asphalt shingles and metal roofs, featuring a slip-resistant polyester surface for worker safety.
• WeatherMaster® Flexible Ice & Water: Ideal for metal roofs and flashing applications, with a plastic film surface for added slip resistance.
• WeatherMaster® Tile: Specifically designed for tile roofs, this underlayment bonds securely with foam adhesives and resists shifting under heavy tile loads.

Fire-resistant slipsheets (FR Slipsheets) enhance a roof’s fire performance. Typically constructed from fiberglass mesh with a flame-retardant coating, these underlayments are commonly used in commercial buildings to meet stringent fire safety codes.

Beyond fire resistance, FR slipsheets can act as a barrier between incompatible insulation and roofing materials, and they can be layered to achieve specific fire ratings.

• FR-10: A coated fiberglass mesh underlayment designed for installation over wood roof decks or combustible insulation, improving fire performance for various commercial roofing systems.

While underlayment may not be visible, its role in protecting a roof is indispensable. Whether prioritizing affordability, cutting-edge technology, specialized applications, or fire safety, selecting the right underlayment ensures long-term performance and peace of mind.