Understanding 15lb Roofing Felt: A Comprehensive Guide: Fast-Track Guide to Choosing the Right Roofing MaterialSarah ThompsonSep 09, 2025Table of ContentsTips 1:FAQTable of ContentsTips 1FAQFree Smart Home PlannerAI-Powered smart home design software 2025Home Design for Free15lb roofing felt, sometimes referred to as 15-pound tar paper, is a traditional underlayment material commonly used in roofing projects. This material is typically made from organic materials like paper or wood fiber, which are then saturated with asphalt. The result is a flexible, moisture-resistant sheet that provides a crucial secondary barrier against water infiltration beneath shingles or other roofing finishes. Particularly valued in residential construction, 15lb roofing felt is praised for its affordability and ease of installation, making it a go-to option for both professional roofers and DIY enthusiasts.When installed properly, roofing felt provides several key benefits: it helps shield the roof deck from wind-driven rain, acts as a temporary barrier if shingles are damaged or removed, and enhances the roof’s fire resistance. It’s most often installed in horizontal layers, overlapping each row to ensure water sheds efficiently. While "15lb" refers to the weight per "square" (a roofing unit covering 100 square feet), it’s important to note that changes in manufacturing standards mean today’s 15lb felt often weighs less than its name implies—usually closer to 7-8 lbs per square. Despite this, it remains widely used as a reliable protective layer.Modern alternatives like synthetic underlayments are growing in popularity due to their lighter weight, durability, and improved performance in extreme weather. However, for many homeowners and contractors, the classic utility and affordability of 15lb roofing felt continue to make it a staple in roof renovation and installation projects. Curious homeowners thinking ahead to their attic or top-floor renovations might also want to coordinate roofing with attic layout or interiors—something that, as a designer, I always advise for a seamless transition between your home’s exterior protection and interior plans. Integrating interior design solutions when planning roof upgrades can enhance not just durability but your overall home aesthetic.Tips 1:When applying 15lb roofing felt, always start installation at the lowest point of the roof and overlap each subsequent row by at least 2 inches to ensure effective water runoff. For the best results, fasten the felt securely but avoid overdriving nails or staples, which can tear the material and reduce its protective capabilities.FAQQ: What is 15lb roofing felt used for? A: 15lb roofing felt is used as an underlayment beneath roofing shingles to provide a moisture-resistant, secondary protective barrier against water infiltration.Q: Is 15lb roofing felt waterproof? A: It is water-resistant but not completely waterproof. Its primary purpose is to offer protection when shingles are compromised or during installation.Q: How does 15lb felt compare to synthetic underlayment? A: Synthetic underlayments are typically lighter, more durable, and offer better protection in extreme weather, but 15lb felt is generally more affordable and time-tested.Q: Can 15lb roofing felt be used for flat roofs? A: While it’s common on sloped roofs, other specialized materials are recommended for flat roofs due to the increased risk of standing water.Q: How long does 15lb roofing felt last? A: While it can last for years when protected by shingles, exposure to the elements without coverage should be minimized, as direct sunlight and water will degrade the material over time.Home Design for FreePlease check with customer service before testing new feature.