Did you know that while metal roofing offers exceptional durability, weather resistance, and longevity, there’s more to its installation than simply fastening panels to your roof? Many homeowners wonder, "Can you put metal roofing directly on plywood?" The straightforward answer is no, but the reasons why might surprise you. This blog will guide you through the essential considerations and steps for installing metal roofing over plywood, ensuring your home remains protected and looks great for years to come. Let’s dive in!

Metal Roofing Directly on Plywood - A Big NO!

Installing metal roofing directly on bare plywood is not recommended. While plywood provides a solid foundation, it lacks the necessary elements to support a metal roof’s long-term performance without additional layers. Let’s explore why:

• Moisture Management: Metal roofs excel at repelling water, but condensation can form underneath the panels. Without an underlayment, moisture trapped between the metal and plywood can lead to rot, mold growth, and even structural damage to your roof and home.
• Thermal Expansion and Contraction: Metal roofing materials expand and contract with temperature changes. If the metal panels are attached directly to plywood, this movement can cause stress, potentially leading to warping, buckling, or damage to the metal itself over time.

The Essential Layers for Installing Metal Roofing on Plywood

To ensure your metal roof performs optimally, a layered installation approach is crucial. Here’s a breakdown of the necessary layers to protect your home:

1. Plywood Sheathing: Start with a solid base of plywood sheathing. Ensure the plywood is in excellent condition, free from any rot or warping. The minimum plywood thickness typically required is 1/2 inch (12.7 mm), but thicker plywood might be necessary depending on your local building codes and the specific metal roofing system you select.
2. Ice and Water Barrier: This layer is a waterproof membrane installed directly over the plywood. It serves as the first line of defense against moisture infiltration, protecting against ice dams, wind-driven rain, and snowmelt.
3. Underlayment: Placed on top of the ice and water barrier, the underlayment (roof felt or synthetic material) acts as a secondary barrier against moisture. It also facilitates thermal movement between the metal panels and the roof deck, which is vital for preventing damage from expansion and contraction.
4. Metal Roof Slip Sheet: A slip sheet, typically made of non-woven fabric or polypropylene, is laid over the underlayment. It allows the metal panels to slide smoothly during thermal expansion and contraction, reducing stress on the panels and preventing scratches or abrasions.
5. Metal Roofing Panels: Finally, the metal roofing panels are installed. These come in various materials (like steel, aluminum, zinc) and styles (such as standing seam, shingles, or panels). Choose a reputable manufacturer and ensure the panels are suitable for your climate’s exposure durability classification or EDC (It refers to a rating that indicates how well roofing materials can withstand various weather conditions and environmental factors.).

How to Install Metal Roofing Over Plywood: A Step-by-Step Overview

Installing metal roofing is a complex task that requires expertise and precision. While DIY installations are possible, it’s often best to hire a licensed roofing contractor to ensure proper installation and avoid costly mistakes. Here’s an overview of what a professional installation involves:

• Proper Ventilation: Adequate ventilation is crucial for preventing moisture buildup under the metal roof, especially in attic spaces. A professional will install vent pipes, soffit vents, or ridge vents to ensure balanced airflow.
• Flashing Installation: Metal flashing is installed around chimneys, vents, pipes, and other roof penetrations to create watertight seals. Proper flashing techniques are essential to prevent leaks.
• Seaming and Fastening: Metal panels are secured using specialized techniques like seaming or mechanical fasteners. A skilled roofer ensures that the panels are securely attached and that the roof has an aesthetically pleasing finish.

Metal Roof on Plywood or OSB: Which is Better?

You might wonder whether plywood or Oriented Strand Board (OSB) is the better choice for roof sheathing. Both materials can serve as a base for metal roofing, but there are differences:

• Plywood is generally more moisture-resistant and durable than OSB, making it the preferred choice for most roofing applications. It’s more resistant to warping and holds up better under long-term exposure to moisture.
• OSB is a cost-effective alternative and can work well if it’s labeled for roof sheathing and properly installed. However, it’s typically less moisture-resistant than plywood, so it’s essential to use high-quality underlayment and other protective layers.

Discuss these options with your roofing contractor to determine the best choice for your specific needs and local climate conditions.

Can You Have a Metal Roof Without Plywood?

While it’s technically possible to install metal roofing without plywood (using solid wood purlins or prefabricated roof panels), this method is less common and typically reserved for specific building types or climates. For most residential applications, plywood sheathing remains the preferred base due to its stability and compatibility with various roofing systems.

Conclusion: Trust the Experts at Astro Roofing for Your Metal Roofing Needs!

When it comes to installing metal roofing, ensuring a proper foundation and following the correct installation steps are crucial for achieving a durable and weather-resistant roof. While metal roofing over plywood is a popular choice for many homeowners, it’s essential to consider all the necessary layers and professional installation techniques to protect your home.

At Astro Roofing, we specialize in comprehensive roofing solutions, including expert metal roof installations over plywood. Our experienced team is here to help you select the best roofing materials and ensure a flawless, long-lasting installation. Contact us today at (253)-459-9703  or visit our website to learn more about our services and schedule a consultation. 

Let us help you protect your home with a roof that offers both beauty and resilience!