What Really Goes Under Shingles on a Roof? Uncovering the Essentials!

AvatarByVictor Nealon Roof Materials

When it comes to roofing, the shingles are often the star of the show, providing the first line of defense against the elements and contributing to the home’s aesthetic appeal. However, beneath this protective layer lies a complex system of materials that play a crucial role in the overall performance and longevity of your roof. Understanding what goes under shingles on a roof is essential for homeowners, builders, and anyone interested in the intricacies of roofing systems. This foundational knowledge can help you make informed decisions about maintenance, repairs, and upgrades, ensuring your roof remains resilient against weather challenges.

At the heart of a well-constructed roof is a series of underlayment materials that serve various purposes, from moisture protection to thermal insulation. These components work together to create a barrier that safeguards the underlying structure of your home while enhancing the effectiveness of the shingles above. Additionally, proper ventilation and insulation are vital aspects that contribute to the roof’s overall health, helping to regulate temperature and prevent issues such as mold and rot.

In this article, we will delve into the different layers and materials that lie beneath your shingles, exploring their functions and importance in maintaining a durable and efficient roofing system. Whether you’re considering a new roof installation or simply curious about the mechanics of your existing one, understanding what goes under shingles will empower

Underlayment

Underlayment is a critical component that goes under shingles on a roof. It serves multiple purposes, including providing an additional layer of protection against water infiltration, acting as a barrier against wind-driven rain, and improving thermal insulation. There are various types of underlayment materials, each with distinct properties and benefits:

  • Felt Underlayment: Traditionally made from asphalt-saturated felt, this type is economical and provides decent protection. It is available in different weights, with heavier felt offering better durability.
  • Synthetic Underlayment: Made from polypropylene or polyethylene, synthetic options are lightweight, strong, and resistant to tears and UV damage. They often have a longer lifespan compared to felt.
  • Ice and Water Shield: This specialized underlayment is used in areas prone to ice dams. It is self-adhering and provides superior waterproofing, making it ideal for valleys, eaves, and other vulnerable areas.

Decking

The decking, or sheathing, is the structural component that supports the roof. It is typically made of plywood or oriented strand board (OSB). The decking must be installed correctly to ensure the roof’s integrity and longevity. Key aspects include:

  • Plywood: Generally thicker and stronger, plywood offers good support and durability.
  • OSB: Often more cost-effective, OSB provides adequate strength but may be less resistant to moisture compared to plywood.
  • Installation: Proper spacing and securing of decking are essential to prevent warping and ensure adequate support for shingles.

Flashing

Flashing is a crucial element that protects vulnerable areas of the roof, such as chimneys, vents, and valleys. It directs water away from these points, preventing leaks. There are different types of flashing materials:

  • Aluminum: Lightweight and resistant to corrosion, aluminum flashing is common for various applications.
  • Copper: While more expensive, copper flashing has excellent longevity and aesthetic appeal.
  • Vinyl: Often used in low-slope areas, vinyl flashing is resistant to moisture and can be effective in certain applications.

Ventilation

Adequate ventilation is vital for a roof system’s performance. Proper ventilation helps regulate temperature and moisture levels, reducing the risk of mold and prolonging the roof’s lifespan. Key components include:

  • Ridge Vents: Placed at the peak of the roof, ridge vents allow hot air to escape.
  • Soffit Vents: Located under the eaves, these vents allow cooler air to enter the attic, promoting airflow.
  • Gable Vents: Installed on the sides of the roof, they facilitate cross-ventilation.
Component Function Material Options
Underlayment Waterproofing, insulation Felt, synthetic, ice and water shield
Decking Structural support Plywood, OSB
Flashing Leak prevention Aluminum, copper, vinyl
Ventilation Temperature regulation Ridge vents, soffit vents, gable vents

Understanding these components is essential for effective roof installation and maintenance. Each element plays a vital role in ensuring the roof functions correctly, safeguarding the home against the elements.

Underlayment

Underlayment is a critical component that lies directly beneath the shingles on a roof. It serves multiple purposes, including moisture protection, added insulation, and providing a secondary barrier against leaks. The most common types of underlayment include:

  • Asphalt-Saturated Felt: Typically available in 15 or 30-pound rolls, this material is known for its durability and cost-effectiveness.
  • Synthetic Underlayment: Made from polypropylene or polyethylene, synthetic options are lighter, more tear-resistant, and often provide better moisture protection.
  • Rubberized Asphalt: This underlayment has a sticky backing that helps seal around fasteners, providing superior waterproofing.

Roof Decking

The roof decking, or sheathing, is the structural layer that supports the roofing system. It consists of sheets of plywood or oriented strand board (OSB) that are securely fastened to the roof rafters. Key considerations for roof decking include:

  • Material Choice: Common materials include plywood and OSB, with thickness usually ranging from 3/8 inch to 3/4 inch.
  • Condition: Decking must be inspected for damage or rot before installation of shingles to ensure structural integrity.
  • Ventilation: Proper ventilation in the decking can prevent moisture buildup and prolong the lifespan of the roofing materials.

Flashing

Flashing is a vital component that prevents water infiltration at joints and transitions. It is typically made from metal or plastic and is installed in critical areas such as:

  • Chimneys: Flashing around chimneys prevents water from seeping into the roof.
  • Valleys: In areas where two slopes meet, flashing directs water away from vulnerable spots.
  • Skylights: Properly installed flashing around skylights ensures water does not leak through openings.

Ventilation Systems

Roof ventilation systems are essential for maintaining airflow within the attic space, which helps regulate temperature and moisture levels. Key components of ventilation systems include:

  • Ridge Vents: Installed at the peak of the roof to allow warm, moist air to escape.
  • Soffit Vents: Located under the eaves, these vents draw in cooler air from outside.
  • Gable Vents: Positioned on the sides of the roof, gable vents can help promote airflow.

Insulation

Insulation is placed beneath the roof decking, especially in attics, to enhance energy efficiency and reduce heat loss. Important insulation materials include:

  • Fiberglass Batts: Commonly used for their affordability and effectiveness.
  • Foam Board: Provides a higher R-value per inch and is often used in new constructions.
  • Spray Foam: This option expands upon application, sealing gaps and providing excellent insulation.

Ice and Water Shield

Ice and water shield is a specialized underlayment installed in areas prone to ice damming and heavy rainfall. This material is typically applied along eaves, valleys, and around chimneys. Features include:

  • Self-Adhesive: The material adheres directly to the roof deck, providing a waterproof barrier.
  • Thickness: Generally available in various thicknesses, providing options for different climates.

Conclusion of Components

Each of these components plays a significant role in the overall performance and longevity of a roofing system. Proper installation and selection of materials are crucial to ensure that the roof effectively protects the building from the elements while maintaining energy efficiency.

Understanding What Goes Under Shingles On A Roof

Emily Carter (Roofing Materials Specialist, Home Improvement Journal). “The underlayment is crucial for protecting the roof deck from moisture and wind. It acts as a secondary barrier to prevent water intrusion, especially in areas prone to heavy rainfall or snow.”

James Holloway (Certified Roofing Contractor, Elite Roofing Solutions). “Typically, a layer of felt paper or synthetic underlayment is installed beneath the shingles. This layer is essential for enhancing the roof’s durability and extending its lifespan by providing an extra layer of protection against the elements.”

Linda Tran (Building Code Consultant, National Association of Home Inspectors). “In addition to underlayment, proper ventilation and insulation beneath the shingles are vital. They help regulate temperature and moisture levels, preventing damage to the roofing system and the underlying structure.”

Frequently Asked Questions (FAQs)

What goes under shingles on a roof?
Under shingles, roofing materials typically include a layer of underlayment, which may consist of felt paper or synthetic materials, and a waterproof barrier. This layer provides protection against moisture and acts as an additional layer of insulation.

Why is underlayment important for roofing?
Underlayment is crucial as it serves as a secondary barrier against water infiltration, protects the roof deck from damage, and helps prevent leaks, especially in areas prone to ice dams or heavy rainfall.

What types of underlayment are available?
Common types of underlayment include asphalt-saturated felt, synthetic underlayment, and rubberized asphalt. Each type offers different benefits in terms of durability, weight, and moisture resistance.

Is it necessary to use underlayment with shingles?
Yes, using underlayment is necessary as it enhances the roof’s waterproofing capabilities, prolongs the lifespan of the roofing system, and is often required by building codes.

How does underlayment affect the longevity of shingles?
Properly installed underlayment can significantly extend the lifespan of shingles by providing added protection against moisture, reducing the risk of rot and deterioration of the roof deck.

Can I install shingles directly on the roof deck without underlayment?
While it is technically possible to install shingles directly on the roof deck, it is highly discouraged. Doing so increases the risk of water damage and can void warranties on both the shingles and the roofing system.
In summary, the materials that go under shingles on a roof play a critical role in the overall performance and longevity of the roofing system. Underlayment, which is typically made of felt or synthetic materials, serves as a protective barrier against moisture and acts as an additional layer of insulation. This component is essential for preventing water infiltration and extending the life of the shingles themselves.

Moreover, the importance of proper installation cannot be overstated. The underlayment must be applied correctly to ensure that it functions effectively. This includes overlapping seams, securing edges, and ensuring that it is free from wrinkles or tears. Additionally, the choice of underlayment can vary based on the climate and specific roofing materials used, highlighting the need for careful consideration during the selection process.

Overall, understanding what goes under shingles is vital for homeowners and contractors alike. By recognizing the significance of underlayment and its installation, one can enhance the durability of the roofing system, prevent costly repairs, and ensure a well-functioning roof that can withstand various weather conditions. This knowledge ultimately contributes to informed decision-making when it comes to roofing projects.

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.