How to Compare Roof Underlayment


If you can't compare and select the best roofing underlayment, you risk subjecting your roof to tears during installation. Additional risks include moisture or ultraviolet damage. The best roofing underlayments offer you increased protection against rips and moisture, and they also weigh less, which helps installation. Finally, you want to know that your underlayment meets government safety standards.

  • Compare the underlayment's fire-resistance ratings that range from A to C. Although all underlayments provide near equal protection against smoke generation, the primary difference consists of flame spread, which the government measures using a "tunnel test" that indicates the speed and distance fire spreads over a substrate. Concrete mesh board, for instance, receives a score of 0 because it won't burn. Gypsum underlayments' burn performance ranges from 10 to 20, so they receive the highest "A" rating, which describes materials performing at 0 to 25. Few underlayments receive a B rating, but some traditional felt underlayments receive a "C" rating for burn properties of 76 to 200.

  • Review the specifications for moisture-permeation properties; they can range below 1 for moisture barriers and above 1 for moisture retardation. Barriers resist moisture but can't stop it. Moisture retardants stop moisture.

  • Compare the climate zones that consist of hot-and-cold-dry or hot-and-cold-wet. Hot-and-cold-dry works well in western and southwestern states and will not become brittle if left exposed during extended installation periods. Hot-and-cold-wet underlayment protects your home in humid climates or during the winter and protects the home's wall structures and studs during extended installation periods.

  • Identify the material, which can range from asphalt-only to synthetic. For instance, traditional asphalt felt underlayment offers less fire-rating protection or tear resistance, but works well with asphalt or wood shingles as well as ceramic tile. Some synthetic underlayments, however, offers better individual safety and utility ratings, but they work best when matched with specific materials like metal shingles or wood.

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