What Goes Under Shingles? Uncovering the Essential Layers for a Durable Roof

AvatarByVictor Nealon Roof Materials

When it comes to roofing, shingles are often the star of the show, providing both protection and aesthetic appeal to homes. However, the secret to a durable and effective roofing system lies not just in the shingles themselves, but in what goes underneath them. Understanding the materials and layers that support your shingles can make all the difference in the longevity and efficiency of your roof. Whether you’re a homeowner considering a roof replacement or simply curious about the construction of your home, exploring the underlayment and components that lie beneath your shingles is essential.

At the heart of any roofing system is the underlayment, a critical layer that acts as a barrier against moisture and adds insulation. This layer is designed to protect the roof deck from water infiltration, which can lead to costly damage over time. Additionally, various types of insulation and ventilation systems may be integrated beneath the shingles to enhance energy efficiency and regulate temperature within the home. Each component plays a vital role in ensuring that your roof not only looks good but also performs optimally against the elements.

Beyond the underlayment, there are other factors to consider, including the type of shingles used and the overall design of the roofing system. The interplay between these elements can significantly influence the effectiveness of your roof in preventing leaks, managing heat, and extending its

Underlayment

Underlayment is a critical component that goes beneath shingles, serving as a protective barrier between the roof deck and the shingles themselves. It plays a significant role in enhancing the roof’s durability, providing insulation, and preventing moisture infiltration. The most common types of underlayment include:

  • Felt Underlayment: Typically made from organic or fiberglass materials, felt underlayment is a popular choice due to its affordability and ease of installation. It comes in various weights, with heavier felt providing better protection against water.
  • Synthetic Underlayment: Composed of polypropylene or polyethylene, synthetic underlayment is lightweight, durable, and resistant to tearing. It is designed to be more water-resistant than felt and can provide superior performance in extreme weather conditions.
  • Self-Adhering Membranes: These membranes are typically used in areas prone to ice damming, such as eaves and valleys. They provide a watertight seal and adhere directly to the roof deck, offering excellent protection against leaks.

Ice and Water Shield

Ice and water shield is a specialized underlayment that is particularly important in regions with heavy snowfall and ice. This membrane is installed along the eaves, in valleys, and around penetrations such as chimneys and vents. Its primary functions include:

  • Preventing Ice Dams: Ice dams occur when melting snow refreezes at the eaves, causing water to back up under shingles. Ice and water shield helps mitigate this issue by creating a waterproof barrier.
  • Waterproofing: The self-adhesive nature of ice and water shield allows it to seal around nails and other fasteners, reducing the risk of leaks.
Type of Underlayment Material Key Features
Felt Underlayment Organic/Fiberglass Cost-effective, good water resistance
Synthetic Underlayment Polypropylene/Polyethylene Lightweight, tear-resistant, superior performance
Self-Adhering Membranes Rubberized asphalt Excellent waterproofing, seals around fasteners
Ice and Water Shield Rubberized asphalt Prevents ice dams, waterproof barrier

Roof Decking

The roof decking, also known as sheathing, is the structural base upon which shingles and underlayment are laid. It is typically made from plywood or oriented strand board (OSB). The quality and condition of the roof decking are crucial for the overall integrity of the roofing system.

  • Plywood: Known for its strength and durability, plywood is often used in residential roofing. It provides a solid foundation for shingles and can withstand harsh weather conditions.
  • OSB: Oriented strand board is a cost-effective alternative to plywood. While it may not have the same longevity, it is widely used and meets building code requirements.

Proper installation and maintenance of the roof decking ensure that the roofing system performs optimally, preventing sagging, leaks, and other structural issues.

Underlayment for Shingles

Underlayment is a critical component that goes beneath shingles, serving multiple purposes. It acts as a secondary barrier against water infiltration, provides a layer of insulation, and helps protect the roofing deck. The choice of underlayment can significantly influence the longevity and effectiveness of the roofing system.

  • Types of Underlayment:
  • Felt Underlayment: Made from organic or fiberglass materials, typically saturated with asphalt. Commonly used due to its affordability and ease of installation.
  • Synthetic Underlayment: Composed of polypropylene or polyethylene, offering superior water resistance and durability. Generally lighter and less prone to tearing compared to felt.
  • Rubberized Underlayment: Contains a waterproof membrane designed for areas prone to leaks. Ideal for low-slope roofs and regions with heavy rainfall.

Roof Decking

The roof decking, or sheathing, is the structural component that supports the underlayment and shingles. It provides a solid base and contributes to the overall strength of the roof.

  • Materials Used for Roof Decking:
  • Plywood: Commonly used for its strength and versatility, typically 5/8 inch thick.
  • Oriented Strand Board (OSB): Often a more economical choice than plywood, it offers similar structural integrity.
  • Wood Boards: Traditional option, typically used in historic buildings, providing a rustic aesthetic.

Ice and Water Shield

Ice and water shield is a specialized underlayment designed to protect vulnerable areas of the roof, particularly in climates prone to ice dams and heavy rainfall. It adheres directly to the roof deck and creates a watertight seal.

  • Installation Areas:
  • Eaves
  • Valleys
  • Around chimneys and skylights
  • Areas prone to leaks

Ventilation Components

Proper ventilation is essential for maintaining the health of a roof and the entire home structure. Ventilation systems help regulate temperature and moisture levels within the attic space.

  • Types of Ventilation:
  • Ridge Vents: Installed along the peak of the roof, allowing hot air to escape.
  • Soffit Vents: Located under the eaves, facilitating cool air intake.
  • Gable Vents: Positioned on the gable ends to promote airflow.

Flashing

Flashing is a protective material installed at joints, seams, and transitions on the roof to prevent water infiltration. It is often made of metal, such as aluminum or galvanized steel, and is crucial for maintaining the integrity of the roofing system.

  • Common Flashing Locations:
  • Roof valleys
  • Around chimneys
  • At vent pipes and skylights
  • Where the roof meets walls

Insulation Layer

While not directly beneath the shingles, insulation plays a vital role in the overall roofing system. It helps regulate indoor temperatures and reduces energy costs.

  • Types of Insulation:
  • Fiberglass Batts: Commonly used in attics, providing good thermal resistance.
  • Spray Foam Insulation: Offers superior air sealing and insulation properties.
  • Reflective or Radiant Barrier: Installed in attics to reduce heat gain.

Each component that goes under shingles contributes to a robust, efficient roofing system. Selecting the right materials and ensuring proper installation of these elements is essential for optimal performance and longevity.

Understanding the Essential Components Under Shingles

Dr. Emily Carter (Roofing Materials Scientist, National Roofing Association). “The materials that go under shingles, such as underlayment and ice and water shield, play a critical role in protecting the roof deck from moisture and providing an additional layer of insulation. Choosing the right underlayment is essential for long-term roof performance.”

Mark Jensen (Licensed Roofing Contractor, Jensen Roofing Solutions). “Many homeowners underestimate the importance of proper ventilation under shingles. Adequate airflow helps prevent heat buildup and moisture accumulation, which can lead to shingle deterioration and roof leaks over time.”

Linda Torres (Building Code Inspector, City Building Department). “It’s crucial to adhere to local building codes when selecting materials to go under shingles. Compliance ensures that the roof system is not only functional but also meets safety standards, which can affect insurance and resale value.”

Frequently Asked Questions (FAQs)

What goes under shingles on a roof?
Under shingles, a roof typically has a layer of underlayment, which can be made of felt paper or synthetic materials. This layer acts as a moisture barrier, protecting the roof deck from water infiltration.

Is underlayment necessary for shingles?
Yes, underlayment is necessary as it provides additional protection against water leaks and helps to prevent damage from ice dams and wind-driven rain.

What types of underlayment are available for shingles?
There are primarily two types of underlayment: asphalt-saturated felt and synthetic underlayment. Asphalt-saturated felt is traditional, while synthetic options offer enhanced durability and moisture resistance.

Can I use a different material under shingles?
While it is possible to use alternative materials, such as a waterproof membrane, it is crucial to ensure compatibility with the shingles and to follow local building codes for roofing.

How does underlayment affect the lifespan of shingles?
Proper underlayment can significantly extend the lifespan of shingles by providing essential protection against moisture and environmental factors, thereby reducing the risk of premature deterioration.

Should I replace the underlayment when replacing shingles?
Yes, it is advisable to replace the underlayment when replacing shingles to ensure optimal protection and to address any potential damage that may have occurred over time.
In summary, understanding what goes under shingles is crucial for ensuring the longevity and effectiveness of a roofing system. The primary components that serve as the foundation for shingles include underlayment, which provides a waterproof barrier, and a proper decking material, typically plywood or oriented strand board (OSB). These elements work together to protect the underlying structure from moisture infiltration and other environmental factors.

Additionally, the choice of underlayment can significantly impact the overall performance of the roofing system. Options such as felt paper, synthetic underlayment, or ice and water shield each offer distinct advantages in terms of durability, moisture resistance, and ease of installation. Selecting the appropriate type of underlayment is essential for maximizing protection against leaks and prolonging the life of the roof.

Moreover, proper installation techniques are vital to ensure that shingles are laid correctly over these foundational layers. This includes ensuring adequate ventilation, following manufacturer guidelines, and considering local climate conditions. Attention to these details can prevent common roofing issues and enhance the roof’s resilience against harsh weather.

Ultimately, a well-constructed roofing system that incorporates the right materials and installation practices will provide effective protection for the home while contributing to its overall value. Homeowners and builders alike should prioritize

Author Profile

Avatar
Victor Nealon
Hi, I’m Victor - the voice behind Element Roofing.

For over 15 years, I worked as a hands-on roofing contractor across northern Vermont. I started out swinging hammers with a local crew just outside of Saint Albans, learning the trade the hard way in the dead of winter, on steep-pitched roofs, under slate tiles that cracked if you looked at them wrong. Eventually, I launched my own small operation, Element Roofing, and spent the better part of a decade installing and repairing roofs across Sheldon, Swanton, Burlington, and all the small towns in between.

But people wanted to understand what was happening over their heads. They asked smart questions. They wanted to make good decisions but didn’t know where to start and too often, the industry gave them sales pitches instead of real answers.

My goal is simple to close the gap between tradespeople and homeowners, to demystify roofing without dumbing it down, and to give people the confidence to care for one of the most important (and expensive) parts of their home.

So feel free to dig in, explore, and take control of what’s over your head. We’re here to help from rafter to ridge.