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What Is Under Shingles on a Roof? Layers Explained | SRS
by Liubomyr Lukaniuk October 17, 2024

What Is Under Shingles on a Roof? Layers Explained | SRS

The shingles you see on a roof are just the outer layer of protection. But have you ever wondered, what is under shingles on a roof? Beneath the shingles lie several crucial layers that help keep your home safe from weather damage, moisture, and extreme temperatures. These layers work together to extend the life of your roof and improve your home's energy efficiency.

In this guide, we’ll explain what is under shingles on a roof, the materials used, and why they matter. Whether you are replacing your roof or just curious, understanding these layers helps you make informed decisions about roofing maintenance and upgrades.

1. What Is Under Shingles on a Roof? An Overview

So, what is under shingles on a roof? There are multiple layers under the shingles, each designed to protect and support the structure. Key materials like the roof deck, underlayment, and flashing all serve unique purposes. Together, they ensure your roof stands strong against rain, wind, and heat. These materials also keep your home dry and help manage heat buildup in the attic.

Understanding these layers will help you appreciate the complexity of a roof and why proper installation is critical.

2. The Roof Deck: The Foundation Beneath Shingles

The roof deck is the first layer to consider when thinking about what is under shingles on a roof. This deck forms the base of your roof, holding up all the layers above it. Usually made from plywood or oriented strand board (OSB), it provides the structure upon which all other roofing materials rest.

a. Types of Roof Decking

  • Plywood: A popular choice for its strength and durability, plywood consists of thin layers of wood veneer glued together.
  • Oriented Strand Board (OSB): OSB is a less expensive alternative to plywood but still strong enough to support the roofing system.

b. Why the Roof Deck Matters

The roof deck supports the weight of the shingles and other roofing materials. It also resists weather-related stresses, like heavy snow or wind. A weak or damaged deck can cause serious problems like sagging or roof leaks, which is why this layer is so important.

3. Roofing Underlayment: A Vital Moisture Barrier

Another key element under shingles on a roof is the roofing underlayment. It acts as a secondary barrier that protects the roof deck from moisture, especially when shingles fail.

a. Types of Roofing Underlayment

  • Asphalt-Saturated Felt: This is one of the oldest and most traditional underlayment options. It provides basic moisture protection and is often used in residential roofing.
  • Synthetic Underlayment: Made from lightweight materials like polypropylene or polyethylene, synthetic underlayment is stronger and more durable than felt.
  • Rubberized Asphalt Underlayment: This waterproof underlayment works well in areas prone to leaks, such as valleys and around chimneys.

b. Importance of Roofing Underlayment

Underlayment provides extra moisture protection. It keeps water from reaching the roof deck if it penetrates the shingles. This layer is essential in protecting your roof from leaks, especially during heavy rain or snow.

4. Ice and Water Shield: Extra Protection in Key Areas

Next on the list of what is under shingles on a roof is the ice and water shield. This sticky, waterproof membrane is applied to areas prone to leaks, such as valleys, eaves, and edges.

a. What Is Ice and Water Shield?

Ice and water shield consists of a rubberized asphalt material. It creates a watertight barrier to prevent leaks, particularly in places where ice dams can form or water tends to pool.

b. Where Is Ice and Water Shield Used?

  • Roof Valleys: Water naturally collects in roof valleys, making them vulnerable to leaks.
  • Eaves: Ice dams can form along the roof’s edge during winter, causing water to back up under shingles. Ice and water shields stop this water from reaching the deck.
  • Chimneys and Skylights: Areas around chimneys and skylights are weak spots where water can easily enter. Adding this shield helps keep these areas dry.

5. Flashing: Sealing the Gaps

Flashing is another crucial component found under shingles on a roof. It seals areas where the roofing material meets other structures, like chimneys, skylights, or walls. Typically made from metal, flashing directs water away from these vulnerable areas, preventing leaks.

a. Types of Flashing

  • Step Flashing: Used where the roof meets a vertical wall, step flashing directs water away from the joint.
  • Vent Flashing: This flashing surrounds pipes or vents that pass through the roof, sealing the gap and keeping water out.
  • Continuous Flashing: Installed along roof edges, it channels water away to prevent pooling and leaks.

b. Why Flashing Is Important

Flashing prevents water from seeping into places where shingles can’t provide full coverage. Without it, these areas would easily develop leaks, which could lead to water damage inside your home.

6. Roof Ventilation: Regulating Temperature and Moisture

When thinking about what is under shingles on a roof, proper ventilation plays a big role. Roof ventilation helps regulate air circulation in the attic, preventing heat buildup and reducing moisture.

a. Types of Roof Ventilation

  • Ridge Vents: Located at the peak of the roof, ridge vents allow warm air to escape from the attic.
  • Soffit Vents: Positioned under the eaves, soffit vents allow cool air to enter the attic.
  • Gable Vents: These vents are installed in the gable ends of the roof to improve airflow.

b. Why Ventilation Is Crucial

Without proper ventilation, heat can build up in the attic, making your home hotter in the summer and causing moisture to accumulate in the winter. This can lead to mold growth and weaken your roof structure.

7. Drip Edge: Directing Water Away

Another element often overlooked when discussing what is under shingles on a roof is the drip edge. The drip edge is a metal strip installed along the edges of the roof. It directs water into the gutters, protecting the roof structure and fascia.

a. What Does the Drip Edge Do?

The drip edge helps prevent water from seeping back under the shingles and into the fascia. It ensures that water flows directly into the gutters, keeping the edges of the roof dry.

b. Drip Edge Materials

Most drip edges are made from aluminum or galvanized steel, both of which resist rust and corrosion.

8. Roofing Insulation: Improving Energy Efficiency

Roofing insulation plays an indirect role in what is under shingles on a roof but is still important. Proper insulation helps regulate the temperature in your home and prevents heat loss or heat buildup in the attic.

a. Types of Insulation

  • Batt Insulation: Fiberglass batts are installed between the rafters in the attic to reduce heat transfer.
  • Spray Foam Insulation: Applied as a liquid that expands, spray foam fills gaps and provides superior insulation.
  • Blown-In Insulation: This loose insulation is spread evenly in the attic, offering excellent coverage.

b. Why Insulation Matters

Good insulation reduces energy costs by maintaining a stable temperature in your home. It also prevents excessive heat in the attic, which can damage the roof structure over time.

9. Conclusion: Understanding What Is Under Shingles on a Roof

To sum up, what is under shingles on a roof consists of multiple layers that protect your home. From the roof deck to the underlayment, flashing, and ice and water shields, each layer serves a specific purpose. Together, these components keep your roof durable, energy-efficient, and resistant to weather-related damage.

By understanding these elements, you can better maintain your roof and make informed decisions about repairs or upgrades. Whether you're looking to replace your roof or just ensure it’s in good shape, knowing what is under shingles on a roof helps you take the right steps for long-term protection.


FAQs

  1. What is under shingles on a roof that supports the shingles?
    The roof deck, usually made of plywood or OSB, supports the shingles and other layers.

  2. What is under shingles on a roof to prevent water damage?
    Roofing underlayment acts as a secondary moisture barrier, protecting the roof deck from water.

  3. What is under shingles on a roof in areas prone to ice dams?
    Ice and water shield is installed in vulnerable areas like valleys and eaves to prevent leaks from ice dams.

  4. What is under shingles on a roof around chimneys and vents?
    Flashing is used around chimneys, skylights, and vents to seal gaps and prevent leaks.

  5. What is under shingles on a roof to control attic temperature?
    Roof ventilation systems, like ridge and soffit vents, help regulate temperature and moisture in the attic.

  6. What is under shingles on a roof that protects the edges?
    The drip edge directs water into the gutters, preventing damage to the roof’s edge and fascia.

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