The choice of roofing underlayment can influence waterproofing, installation speed, and long-term durability. 90 Lb Felt For Roofing refers to a heavy-duty asphalt-saturated underlayment designed to provide a resilient secondary barrier beneath shingles or other roofing materials. This guide explains what 90 lb felt is, why builders select it, how it’s installed, and how it compares with other underlayments. It will help homeowners and contractors understand when and where 90 lb felt is the right option.
What Is 90 Lb Felt For Roofing?
90 lb felt is a type of asphalt-saturated roofing underlayment with a high grammage per 100 square feet, indicating dense, tough material. Traditionally sold in rolls measured by weight, it offers better tear resistance and puncture resistance than lighter felts. It’s typically used as a secondary moisture barrier on steep-slope roofs and can be installed as a self-sealing or unsealed layer, depending on the product and installation method. Homeowners may encounter 90 lb felt in older or higher-end residential projects, as well as in some commercial applications that require robust underlayment performance.
Why Builders Choose 90 Lb Felt
The primary advantages of 90 lb felt include enhanced durability, improved resistance to wind uplift, and extended protection during construction. Compared with lighter felts, it resists tearing and provides extra protection during roof deck exposure before shingles are installed. It also tends to perform well in cooler temperatures, where lighter felts can become brittle. In coastal or storm-prone regions, the extra thickness helps reduce the risk of moisture intrusion from wind-driven rain. Additionally, some 90 lb felts are designed for use with self-adhesive systems, offering easier installation and better wind resistance in certain formats.
Installation Basics
Proper installation is essential to maximize the performance of 90 lb felt. Here are core practices to follow:
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- Surface Preparation: Ensure the roof deck is dry, clean, and free of protrusions or sharp edges that could compromise the felt.
- Overlap and Alignment: Install rolls starting at the eave, with typical horizontal overlaps of 19 inches for self-adhesive systems or conforming to product instructions. Vertical seams should be offset to reduce potential leaks.
- Fastening or Adherence: If using a non-self-adhesive 90 lb felt, fasten per manufacturer guidance, typically with corrosion-resistant nails or staples. Self-adhesive varieties require a protective release film and may need a primer on certain decks.
- Weather Considerations: Do not install in rain or snow. Temperature affects adhesion and lay-flat behavior; hot or cold extremes can impact performance.
- Roofing Material Compatibility: Ensure compatibility with the final roofing layer (asphalt shingles, metal, tile, etc.) and verify any warranty requirements from the shingle or roofing system manufacturer.
Durability, Weather Resistance, And Codes
90 lb felt offers notable durability, including improved tear resistance and puncture tolerance during installation and while the roof is exposed. It provides a secondary moisture barrier in case the primary roofing layer is compromised. In terms of codes, building requirements vary by jurisdiction. Several regions mandate asphalt-saturated felt or an approved equivalent as the underlayment for steep-slope roofs, sometimes specifying wind-driven rain zones and installation patterns. Hydrophobic performance, UV resistance, and compatibility with self-adhering systems are important considerations that can influence code compliance and warranty terms. Always verify local code adoption and the roofing manufacturer’s guidelines before choosing 90 lb felt for a given project.
Comparing 90 Lb Felt With Other Underlayments
When evaluating underlayments, the weight category is a key differentiator. Here is a concise comparison to help decision-making:
- Lightweight Felts (e.g., 15-30 lb): Easier to handle and cheaper, but less tear and puncture resistance; may require more care in wind-prone areas.
- 90 Lb Felt: Heavier, tougher, better wind resistance and durability; typically used in regions with harsh weather or higher-quality installations. Can be self-adhesive in some products for easier installation and improved seal.
- Self-Adhering Underlayment: Provides immediate adhesion, excellent wind resistance, and faster installation in some climates; can come in high weight formulations but is often marketed as 60-90 lb equivalent in performance.
- Synthetic Underlayments: Lightweight, tear-resistant, and quick-drying; often used for modern roof systems and lasting performance with fewer moisture issues, though price and compatibility vary.
Practical Considerations And Maintenance
For long-term performance, consider these practical factors:
- Climate Alignment: In regions with heavy rainfall, snow, or wind, a heavier underlayment like 90 lb felt may offer additional protection during construction and in wet seasons.
- Ventilation And Condensation: Underlayment cannot compensate for poor attic ventilation. Ensure proper ventilation to minimize condensation risks that could affect roof deck integrity.
- Warranty And Manufacturer Requirements: Some roofing warranties specify specific underlayment types and installation methods. Align 90 lb felt selections with warranty terms to avoid coverage gaps.
- Repairability: If underlayment damage occurs, replace according to manufacturer guidelines to maintain system performance. Heavier felts may require careful removal and reapplication.
Costs, Availability, And Project Planning
90 lb felt generally costs more per square than lighter underlayments due to material density and durability. Availability varies by region and supplier, with larger home improvement centers and roofing distributors carrying compatible products. For project planning, budget for the underlayment cost, potential labor differences in handling heavier rolls, and any added disposal or recycling considerations. When evaluating total roof costs, factor in how the underlayment choice affects warranty terms, installation speed, and the expected lifespan of the roof system.
Choosing The Right Underlayment For Your Roof
Selecting between 90 lb felt and other underlayments depends on climate, roof design, budget, and warranty terms. For steeper, high-wind projects in regions with severe weather, 90 lb felt can provide an extra margin of protection during construction and exposure. In milder climates or modern installations favoring fast, synthetic solutions, lighter or synthetic underlayments may be preferable. Consulting with a licensed roofing contractor can help determine the optimal underlayment based on local codes, roof design, and the chosen roofing materials.
Installation Summary For 90 Lb Felt
To summarize the practical steps:
- Prepare the deck and ensure dryness.
- Lay the underlayment with correct overlaps as per product instructions.
- Use the appropriate fasteners or adhesive for the selected variant.
- Proceed with the final roofing material installation following manufacturer recommendations.