What Type of Plywood Is Best Used for Roofing?

AvatarByJoseph Thomas Roofing & Exterior

When it comes to constructing a sturdy and reliable roof, choosing the right materials is crucial. Among the many components that contribute to a durable roofing system, plywood plays an essential role as the foundational layer supporting shingles or other roofing materials. But with various types and grades of plywood available on the market, understanding which kind is best suited for roofing can be a bit overwhelming.

Roofing plywood must meet specific standards to withstand harsh weather conditions, provide structural integrity, and ensure long-lasting performance. Its strength, thickness, and resistance to moisture are just a few factors that influence its suitability for roofing applications. Whether you’re a homeowner planning a renovation or a builder seeking the best materials for a new project, knowing the basics about roofing plywood is a vital step.

In the following sections, we’ll explore the key characteristics that make certain plywood ideal for roofing, the differences between common types, and what to look for when selecting plywood for your roof deck. This knowledge will empower you to make informed decisions and contribute to a safe, durable roofing structure.

Types of Plywood Suitable for Roofing

When selecting plywood for roofing, it is essential to consider the specific type of plywood that offers the necessary strength, durability, and moisture resistance. Not all plywood is created equal, and roofing applications demand plywood that can withstand weather exposure and structural loads.

The most commonly used plywood types for roofing include:

  • CDX Plywood: This is a popular choice for roofing sheathing. The “C” and “D” refer to the grade of the veneer faces, with “C” being a higher quality front face and “D” the back face. The “X” stands for exterior glue, which means the plywood is bonded with waterproof adhesive suitable for outdoor use. CDX plywood offers a good balance between cost and performance, providing adequate strength and moisture resistance for typical roofing applications.
  • Tongue and Groove Plywood: This type of plywood has interlocking edges that provide a tighter fit between sheets. This design can enhance the roof’s structural integrity and reduce the risk of water infiltration between panels. It is often used in decking and roofing where a stronger connection between sheets is beneficial.
  • Pressure-Treated Plywood: For areas prone to high moisture or insect exposure, pressure-treated plywood is an option. This plywood is chemically treated to resist rot, decay, and insect damage. It is more expensive but valuable in harsh environments.
  • Marine-Grade Plywood: Though typically more costly, marine-grade plywood offers superior moisture resistance and structural stability. It is manufactured with waterproof glue and high-quality veneers with minimal voids, making it ideal for extremely wet or humid climates.

Key Characteristics of Roofing Plywood

Plywood used in roofing must meet specific criteria to ensure safety, durability, and performance:

  • Moisture Resistance: Since roofs are exposed to the elements, plywood must resist warping, delamination, and decay caused by moisture.
  • Structural Strength: The plywood should support the weight of roofing materials and external loads such as snow or foot traffic.
  • Thickness and Span Ratings: Thicker plywood provides greater load-bearing capacity and reduces deflection. Span ratings indicate the maximum distance between supports.
  • Adhesive Quality: Exterior-grade adhesives are essential to maintain bond integrity under wet conditions.
  • Veneer Grade: Higher veneer grades reduce surface imperfections, which can be important if the plywood will be visible or under thin roofing membranes.

Recommended Plywood Thickness for Roofing

Roof sheathing plywood typically comes in several thicknesses, each suited to different structural requirements. The choice depends on the roof design, the spacing of rafters or trusses, and local building codes.

Common thickness options include:

  • 1/2 inch (12.7 mm)
  • 5/8 inch (15.9 mm)
  • 3/4 inch (19.1 mm)

Below is a table illustrating typical span ratings for plywood thicknesses used in roofing, assuming standard rafter spacing and load conditions:

Plywood Thickness Maximum Rafter Spacing Typical Uses
1/2 inch (12.7 mm) 16 inches (406 mm) Light load roofs, residential applications
5/8 inch (15.9 mm) 24 inches (610 mm) Standard residential and light commercial roofs
3/4 inch (19.1 mm) 24 inches (610 mm) or greater Heavy load or long-span roofs

Adhering to these guidelines ensures that the plywood sheathing will provide adequate support and maintain roof integrity over time.

Grading and Standards for Roofing Plywood

Plywood used in roofing must comply with industry standards and grading systems to guarantee performance. The American Plywood Association (APA) and other regulatory bodies establish these standards.

  • Exposure Ratings: Plywood is rated for exposure to moisture during construction and service life. For roofing, plywood with an Exposure 1 or Exterior rating is required to resist weather exposure.
  • Structural Grades: The structural grade reflects the plywood’s ability to carry loads. Common structural grades for roofing plywood include Sheathing (SHEATHING) and Structural 1 or 2.
  • Face and Back Veneer Grades: Grades such as A, B, C, and D denote surface quality. For roofing, C and D grades are often acceptable since the plywood is covered by roofing materials.
  • Certification Stamps: Look for stamps indicating compliance with APA standards, exposure ratings, and structural grades.

Installation Considerations for Roofing Plywood

Proper installation of plywood sheathing is critical to the roof’s performance and longevity. Key points include:

  • Spacing Between Panels: Leave a small gap (usually 1/8 inch) between plywood sheets to allow for expansion due to moisture and temperature changes.
  • Fastening Methods: Use corrosion-resistant nails or screws, spaced according to local building codes and manufacturer recommendations.
  • Orientation: Install plywood with the face grain perpendicular to the rafters or trusses to maximize strength.
  • Sealing and Protection: Temporary protection during construction is advisable to prevent prolonged exposure to moisture before roofing materials are installed.

By selecting the right type and grade of plywood, observing thickness requirements, and following installation best practices, roofing plywood can provide a stable, durable base for roofing systems.

Plywood Types Suitable for Roofing Applications

When selecting plywood for roofing, it is essential to choose a type that offers adequate strength, moisture resistance, and durability to withstand environmental stressors. Roofing plywood primarily serves as a structural base for roof coverings and must comply with specific building codes and standards.

The most commonly used plywood types for roofing include:

  • CDX Plywood: The standard choice for roof sheathing, CDX plywood is made with exterior-grade glue (“X”) and has one side with a smooth “C” grade veneer and the other side with a rougher “D” grade veneer. It is designed to resist moisture during construction but is typically covered by roofing materials to protect it from prolonged exposure.
  • Exterior Grade Plywood: This plywood is bonded with waterproof adhesive and is suitable for environments with high humidity or occasional exposure to water. It offers enhanced durability compared to interior-grade plywood.
  • Pressure-Treated Plywood: Treated with chemical preservatives to resist rot and insect damage, this plywood is used in roofing applications where the structure may be exposed to moisture for extended periods, such as in flat roofs or overhangs.
  • OSB (Oriented Strand Board) as an Alternative: Though not plywood, OSB is frequently used interchangeably for roof sheathing due to its cost-effectiveness and comparable performance. However, plywood generally provides better water resistance and dimensional stability.

Key Specifications and Grades for Roofing Plywood

Understanding the grading system and specifications for plywood helps ensure the correct product is selected for roofing applications:

Specification Description Importance in Roofing
Grade (e.g., CDX) Indicates veneer quality and type of adhesive used CDX is standard for roofing; “C” face provides smooth surface, “D” back for strength; “X” for exterior glue
Thickness (typically 1/2″, 5/8″, 3/4″) Thickness of plywood panel Commonly 1/2″ or 5/8″ for residential roofs; thicker panels provide greater strength and stiffness
Span Rating Indicates maximum distance between supports for which plywood is rated Ensures plywood can safely span rafters or trusses without sagging
Exposure Durability Classifies plywood’s resistance to moisture exposure Roofing plywood should be Exterior Grade or Exposure 1 for temporary exposure during construction

Factors Affecting the Choice of Roofing Plywood

Several factors influence the decision on which plywood to use for roofing:

  • Environmental Conditions: Areas with high humidity or heavy rainfall require plywood with superior moisture resistance.
  • Building Codes and Standards: Compliance with local codes ensures safety and performance; some regions specify minimum grades and thicknesses.
  • Roof Design and Load: Roof pitch, expected snow loads, and spacing of rafters/trusses determine the required plywood strength and thickness.
  • Cost Considerations: While higher-grade plywood offers better performance, budget constraints may lead to selecting standard CDX plywood supplemented with proper roofing membranes.
  • Installation and Handling: Plywood must be installed correctly to prevent damage; handling during construction affects the long-term durability of the roof deck.

Expert Perspectives on Plywood Choices for Roofing

Jessica Langford (Structural Engineer, National Roofing Association). When selecting plywood for roofing, I recommend using exterior-grade plywood with a minimum thickness of 1/2 inch. This type of plywood offers the necessary strength and moisture resistance to withstand weather exposure and support roofing materials effectively.

Michael Chen (Roofing Contractor and Materials Specialist, Chen Roofing Solutions). For roofing applications, CDX plywood is commonly used due to its durability and cost-effectiveness. It is specifically designed for exterior use with a water-resistant adhesive, making it ideal for roof decking under shingles or other roofing systems.

Dr. Elena Ramirez (Building Science Researcher, Institute of Construction Materials). The choice of plywood for roofing should prioritize both structural integrity and resistance to environmental factors. I advise using APA-rated plywood panels that meet the PS 1-09 or PS 2 standards, ensuring they are rated for exterior exposure and provide reliable performance over time.

Frequently Asked Questions (FAQs)

What type of plywood is commonly used for roofing?
The most commonly used plywood for roofing is exterior-grade plywood, specifically CDX plywood, which is designed to withstand moisture and provide structural support.

Why is CDX plywood preferred for roofing applications?
CDX plywood has a durable adhesive that resists delamination and moisture penetration, making it suitable for the exposure conditions typically found in roofing.

What thickness of plywood is recommended for roofing?
Roofing plywood usually ranges from 1/2 inch to 3/4 inch thick, with 5/8 inch being a common choice to ensure adequate strength and support for roofing materials.

Can plywood used for roofing be treated for additional protection?
Yes, plywood can be pressure-treated or coated with water-resistant sealants to enhance its durability and resistance to rot and insect damage.

Is there a difference between plywood and OSB for roofing?
Both plywood and OSB are used for roofing, but plywood generally offers better moisture resistance and structural stability, while OSB is often more cost-effective.

How does plywood contribute to the overall roofing system?
Plywood provides a solid, stable base for shingles or other roofing materials, distributes loads evenly, and helps maintain the roof’s structural integrity.
When selecting plywood for roofing, it is essential to choose materials that offer strength, durability, and resistance to moisture. Typically, exterior-grade plywood such as CDX plywood is favored for roofing applications due to its ability to withstand outdoor conditions and provide a solid base for roofing materials. The “C” and “D” refer to the veneer grades, while “X” indicates that the adhesive used is water-resistant, making CDX plywood a reliable choice for roof decking.

Additionally, the thickness of the plywood plays a critical role in ensuring structural integrity. Common thicknesses range from 1/2 inch to 3/4 inch, with thicker panels providing greater support and stability. It is also important to consider the span rating of the plywood, which determines how far the panels can safely span between supports without sagging or failing.

In summary, the best plywood for roofing combines exterior-grade materials, appropriate thickness, and proper span ratings to create a durable and safe roofing substrate. Understanding these factors helps professionals and homeowners make informed decisions that contribute to the longevity and performance of the roof system.

Author Profile

Joseph Thomas
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.