What Is Found Beneath Shingles on a Roof?

When it comes to roofing, shingles are often the first thing that catches the eye—providing both aesthetic appeal and essential protection against the elements. But have you ever wondered what lies beneath those shingles? Understanding what is under shingles on a roof is key to appreciating how a roof functions as a whole system, safeguarding your home from weather, moisture, and structural damage.

Beneath the visible layer of shingles, there is a carefully constructed assembly designed to provide durability and resilience. This hidden structure works quietly to prevent leaks, manage water flow, and support the overall integrity of the roof. Exploring what’s under the shingles reveals the complexity and thoughtfulness involved in roofing, far beyond the surface appearance.

Whether you’re a homeowner curious about your roof’s makeup or someone considering repairs or replacement, gaining insight into the layers beneath shingles can help you make informed decisions. It also highlights why proper installation and maintenance are critical for a roof’s long-lasting performance. In the sections that follow, we’ll delve into the components that lie under shingles and how they contribute to a strong, weather-resistant roof.

Components Found Beneath Roof Shingles

Beneath the visible layer of shingles on a roof, there are multiple layers that work together to protect the structure from weather elements and provide insulation. Understanding these underlying components is crucial for assessing roof health and planning repairs or replacements.

The typical layers found under shingles include:

• Roof Decking: The base layer, usually composed of plywood or oriented strand board (OSB), provides structural support. It forms the solid surface to which shingles and other materials are attached.
• Underlayment: A protective barrier laid directly on the roof decking. It is commonly made from felt paper or synthetic materials and serves as a secondary water-resistant layer.
• Ice and Water Shield: A self-adhesive membrane applied in vulnerable areas such as roof edges, valleys, and around penetrations to prevent leaks from ice dams and wind-driven rain.
• Flashing: Metal strips installed around roof features like chimneys, vents, and skylights to prevent water intrusion at joints and seams.
• Ventilation Components: Includes soffit vents, ridge vents, and baffles that promote airflow and prevent moisture buildup beneath the roof.

Each of these layers plays a vital role in maintaining the roof’s integrity and longevity.

Detailed Breakdown of Roof Underlayment Types

Underlayment is a critical barrier beneath shingles that provides additional protection against moisture and wind. The choice of underlayment depends on climate, roof slope, and budget considerations.

Underlayment Type	Material	Key Features	Typical Use
Asphalt-Saturated Felt	Organic or fiberglass felt impregnated with asphalt	Economical, moderate water resistance, traditional	Most common residential roofs
Synthetic Underlayment	Polypropylene or polyester fabric	Lightweight, durable, superior water resistance, UV resistant	High-end roofing, steep slopes, exposed areas
Rubberized Asphalt Membrane	Rubberized asphalt with a peel-and-stick backing	Self-adhesive, excellent waterproofing, seals around nails	Ice dam-prone regions, valleys, eaves

Flashing and Its Importance Under Shingles

Flashing is essential for preventing water penetration where the roof meets vertical surfaces or where different roof sections intersect. It is typically made of aluminum, galvanized steel, copper, or lead.

Common flashing locations include:

• Roof valleys
• Chimney bases
• Roof-to-wall junctions
• Around skylights, vents, and pipes

Proper installation and maintenance of flashing are critical because even small gaps or corrosion can lead to leaks and significant damage.

Roof Decking and Its Role

The roof decking provides the foundation for all other roofing components. Typically made of plywood or OSB, the decking must be solid and free from rot or warping to support the weight of the roofing materials.

Key considerations for roof decking include:

• Thickness: Generally ranges from 5/8 to 3/4 inch, depending on structural requirements.
• Condition: Must be inspected for water damage or insect infestation during roof replacement.
• Ventilation: Proper ventilation beneath the decking helps prevent moisture buildup, extending roof life.

Additional Protective Layers and Ventilation

Besides the main components, additional layers and features contribute to roof durability:

• Ice and Water Shield: Applied in areas susceptible to ice damming, this membrane offers superior waterproofing by sealing around nails and seams.
• Roof Ventilation Systems: Balanced ventilation through ridge vents, soffit vents, and attic fans reduces heat buildup and moisture, preventing premature material deterioration.
• Drip Edge: Metal strips installed along roof edges to direct water away from the fascia and protect the underlying layers.

Together, these elements enhance the overall performance of the roofing system beneath the shingles.

Components Found Beneath Roof Shingles

The structure beneath roof shingles consists of multiple layers designed to provide waterproofing, insulation, and structural support. Understanding these components is essential for roof maintenance, repair, and replacement.

Directly under the shingles, the following key layers are typically found:

• Roof Decking (Sheathing): This is the solid surface that supports the shingles. Usually made from plywood or oriented strand board (OSB), the roof decking forms the structural base of the roof.
• Underlayment: Installed atop the roof decking, underlayment provides an additional waterproof barrier. Common materials include felt paper (tar paper) or synthetic underlayments.
• Ice and Water Shield: In climates prone to freezing temperatures, a self-adhering membrane is often applied along roof edges, valleys, and eaves to prevent water infiltration from ice dams.
• Flashing: Metal strips or sheets placed around roof penetrations (chimneys, vents, skylights) and valleys to direct water away and prevent leaks.
• Roof Ventilation Components: Though not directly beneath shingles, vents are integral to roof performance, allowing airflow to reduce moisture buildup.

Layer	Material Examples	Primary Function
Roof Shingles	Asphalt, wood, metal, slate, tile	Primary waterproofing and aesthetic finish
Ice and Water Shield	Self-adhering rubberized membrane	Prevents water infiltration from ice dams and wind-driven rain
Underlayment	Felt paper, synthetic membrane	Secondary water barrier, protects decking
Roof Decking (Sheathing)	Plywood, OSB	Structural base for shingles and underlayment
Flashing	Aluminum, galvanized steel, copper	Seals roof penetrations and directs water away

Function and Importance of Each Layer Under Shingles

Each layer beneath the shingles plays a crucial role in the roof’s overall integrity and longevity. Their combined effect ensures protection against weather elements, structural stability, and energy efficiency.

• Roof Decking: Acts as the foundation for the roof system. It must be sturdy and free of damage to support the weight of shingles and resist external forces such as wind and snow loads.
• Underlayment: Serves as a secondary waterproof barrier. In case the shingles are damaged or penetrated, the underlayment prevents water from reaching the decking and causing rot or mold growth.
• Ice and Water Shield: Especially important in colder climates, this membrane adheres tightly to the decking and seals around nails, preventing leaks caused by ice dams or wind-driven rain.
• Flashing: Ensures that water does not enter vulnerable areas such as roof joints, valleys, or around chimneys and vents. Properly installed flashing significantly reduces leak risk.
• Ventilation Components: By allowing air circulation beneath the roof, ventilation helps maintain proper temperature and moisture levels, preventing premature shingle deterioration and structural damage.

Common Materials Used Under Shingles and Their Characteristics

The choice of materials beneath shingles can vary based on budget, climate, and roofing type. Understanding their properties aids in selecting the right combination for optimal performance.

Material	Typical Use	Advantages	Considerations
Plywood	Roof decking	Strong, widely available, easy to install	Can delaminate if exposed to moisture
Oriented Strand Board (OSB)	Roof decking	Cost-effective alternative to plywood	More susceptible to water damage than plywood
Felt Paper (Asphalt-saturated)	Underlayment	Affordable, proven waterproofing	Can tear during installation, less durable than synthetics
Synthetic Underlayment	Underlayment	Lightweight, strong, resistant to tearing	Higher cost, some types less vapor permeable
Rubberized Asphalt Membrane	Ice and water shield Expert Perspectives on What Lies Beneath Roof Shingles Dr. Emily Carter (Building Envelope Specialist, National Roofing Institute). “Underneath roof shingles, you typically find a layer called underlayment, which serves as a critical waterproof barrier protecting the roof deck from moisture infiltration. This underlayment is often made of felt paper or synthetic materials, designed to provide an additional layer of defense against wind-driven rain and ice dams.” Michael Tran (Certified Roofing Contractor, Tran Roofing Solutions). “Beneath the shingles and underlayment lies the roof deck, commonly constructed from plywood or oriented strand board (OSB). The integrity of this deck is essential because it supports the entire roofing system and must be free of rot or damage to ensure long-term durability and structural stability.” Susan Delgado (Architectural Engineer, GreenBuild Consulting). “In modern roofing assemblies, beneath the shingles you may also find ventilation components and sometimes ice and water shields in vulnerable areas. These elements work together to manage moisture and temperature fluctuations, preventing premature deterioration of the roofing materials and enhancing energy efficiency.” Frequently Asked Questions (FAQs) What is typically found under shingles on a roof? Beneath shingles, there is usually an underlayment layer, which acts as a secondary barrier against water infiltration. This underlayment is often made of felt paper or synthetic materials. Why is underlayment important under roof shingles? Underlayment provides additional protection from moisture, helps prevent leaks, and shields the roof deck from damage caused by wind-driven rain or ice dams. What material is used for the roof deck under the underlayment? The roof deck is commonly constructed from plywood or oriented strand board (OSB), serving as the structural base for the roofing system. Can issues under shingles cause roof leaks? Yes, damage or deterioration of the underlayment or roof deck can lead to leaks, even if the shingles appear intact. How can I inspect what is under my roof shingles? Inspection typically requires removing shingles or accessing the attic to check the condition of the underlayment and roof deck for signs of moisture or damage. Does the type of underlayment vary depending on the roof? Yes, the choice of underlayment depends on the roofing material, climate conditions, and building codes, with options ranging from traditional felt to advanced synthetic membranes. Under shingles on a roof, several critical layers work together to protect the structure from weather elements and ensure durability. Directly beneath the shingles is typically a roofing underlayment, such as felt paper or synthetic material, which acts as a moisture barrier. This layer prevents water infiltration in case the shingles are damaged or displaced. Beneath the underlayment lies the roof deck, usually composed of plywood or oriented strand board (OSB), providing the structural foundation for the roofing system. Additional components beneath the shingles may include flashing around roof penetrations and edges to direct water away from vulnerable areas. Proper installation of these layers is essential to maintain the roof’s integrity and prevent leaks, mold growth, and structural damage. Understanding what lies beneath shingles helps homeowners and professionals assess roof conditions and make informed decisions about maintenance or replacement. In summary, the layers under shingles form a comprehensive defense system against environmental factors. Recognizing the role of each layer—from shingles to underlayment to roof deck—highlights the complexity of roofing systems and emphasizes the importance of quality materials and skilled installation for long-lasting roof performance. Author Profile Joseph Thomas I’m Joseph Thomas, a home improvement writer with years of hands-on experience working with residential systems and everyday repairs. Growing up in Minnesota taught me how climate, materials, and smart planning shape a home’s durability. Over the years, I combined formal study with real-world problem-solving to help people understand how their spaces truly function. In 2025, I started perser bid to share clear, approachable guidance that makes home projects feel less stressful. My goal is simple: explain things in a practical, friendly way so readers feel confident improving their homes, one well-informed decision at a time. Latest entries December 23, 2025FlooringHow Can You Stop a Rug from Slipping on a Wood Floor? December 23, 2025Paints & SealantsIs It Safe to Paint While Pregnant? What You Need to Know December 23, 2025FlooringHow Do You Get Milk Out of the Carpet Quickly and Effectively? December 23, 2025PlumbingHow Much Does It Really Cost to Plumb a House?