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The difference between traditional roof underlayment and ice and water shield.

When it comes to roofing, the underlayment is a crucial element that often goes unseen but plays a significant role in protecting your home from the elements. Two common types of underlayment used in roofing are traditional roof underlayment and ice and water shield. In this article, we’ll delve into the key differences between these two materials, shedding light on their unique characteristics and the scenarios in which they are most beneficial.

  1. Traditional Roof Underlayment:
    • Composition: Traditional roof underlayment, often referred to as felt paper or asphalt-saturated felt, is made from a base of organic materials such as cellulose or fiberglass. It is then coated with asphalt to enhance water resistance.
    • Water Resistance: While traditional underlayment provides a level of water resistance, it is not completely impervious to water infiltration. Its primary purpose is to act as a secondary barrier, preventing water that may penetrate the outer roofing material (shingles or tiles) from reaching the roof deck.
    • Installation: Traditional underlayment is typically installed in overlapping layers, starting from the bottom of the roof and working upward. It is secured using staples or nails, creating a protective barrier between the roof deck and the roofing material.
    • Cost: Traditional underlayment is generally more budget-friendly compared to ice and water shield, making it a common choice for standard roofing projects.
  2. Ice and Water Shield:
    • Composition: Ice and water shield, also known as self-adhesive membrane or rubberized asphalt underlayment, is composed of a rubberized asphalt material that is highly flexible and self-adhering. It often has a peel-and-stick backing that adheres directly to the roof deck.
    • Water Resistance: The key advantage of ice and water shield lies in its exceptional water resistance. The self-adhesive nature of the material creates a watertight seal around roofing fasteners, providing superior protection against water infiltration, especially in vulnerable areas such as valleys, eaves, and around roof penetrations.
    • Installation: Ice and water shield is installed in specific areas of the roof that are prone to water penetration. It is commonly used in valleys, around chimneys, skylights, and other potential leak points. The material’s self-adhesive properties create a continuous and secure seal.
    • Cost: Ice and water shield is generally more expensive than traditional underlayment due to its advanced technology and enhanced water resistance. However, the added protection it offers may justify the higher cost, especially in regions prone to heavy rain, ice dams, or severe weather conditions.


Choosing between traditional roof underlayment and ice and water shield depends on various factors, including your budget, climate, and the specific vulnerabilities of your roof. While traditional underlayment serves as a reliable and cost-effective option for standard roofing projects, ice and water shield shines in areas where superior water resistance and protection are paramount. Consulting with a professional roofer and considering your regional climate conditions can help you make an informed decision, ensuring the long-term durability and resilience of your roofing system.

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