Metal Roof Screws On Rib Or Flat? (Homeowners Guide)

When it comes to installing a metal roof, one of the most debated topics among contractors and DIY enthusiasts alike is whether metal roof screws should go into the rib (the raised portion of the metal panel) or the flat (the lower section of the metal panel). This might seem like a simple question, but the placement of screws can significantly affect the:

• Performance
• Longevity
• Durability of your metal roofing system

We’re dedicated to providing the best advice and solutions for roofing projects, so we’ve prepared this thorough guide to help you make the right decision. We’ll explore the arguments for and against each option, discuss best practices, and offer trusted recommendations for securing screws in your metal roofing system.

The Basics of Metal Roofing Screws

Before we discuss whether screws should be fastened on the rib or the flat section, it’s helpful to understand the purpose of metal roof screws and their role in a metal roofing system.

What Do Metal Roof Screws Do?

Metal roof screws are essential components used to fasten metal panels to the underlying structure, ensuring that your roof is securely attached. Typically, screws used in metal roofing feature:

• A secure thread design for dependable grip
• Weather-resistant coatings for durability
• A rubber or neoprene washer to create a watertight seal around the screw

These screws are crucial to keeping your roof intact through wind, rain, and other weather conditions. Proper fastening is integral to maintaining a waterproof, secure, and long-lasting roofing system.

Importance of Correct Screw Placement

Incorrect screw placement can lead to several issues including:

• Roof leaks due to improper sealing
• Compromised structural integrity
• Increased chances of panel shifting
• Accelerated wear of components

That’s why understanding whether screws go on the rib or the flat surface is a topic worth exploring in depth.

Placement Options for Metal Roof Screws

When it comes to securing screws in metal roofing, there are two primary options:

1. On the Flat Area – Screws are fastened directly into the lower sections of the metal panel.
2. On the Rib Area – Screws are fastened into the raised ribs or ridges of the metal panel.

Each method has unique advantages and disadvantages, which we’ll explain in detail below.

Screws on the Flat Section

Many roofing system manufacturers and contractors recommend fastening screws on the flat section of the metal roofing panels. Here’s why.

✅ Advantages of Screws on the Flat

• Stronger Structural Grip: The flat section of a metal panel sits flush against the underlying roof decking or purlins. When screws are driven into the flat area, they have better contact with the solid backing, resulting in a stronger grip. This ensures the panels are securely attached, even during high winds or heavy rain.
• Prevent Panel Flexing: Metal roofing panels expand and contract with temperature changes. Screwing into the ribs can allow for more flexing, which may loosen screws over time. Fastening screws on the flat provides a firm anchor point, minimizing unwanted flexing.
• Easier to Achieve a Watertight Seal: Screws on the flat section press the panel directly against the neoprene washer and substrate, creating a consistent, watertight seal. This reduces the risk of leaks around fastener points.
• Improved Load Distribution: When screws are placed on the flat section, the load and stress on the panels are distributed evenly across the roof decking. This enhances the overall stability of the roof.

❌ Disadvantages of Screws on the Flat

• Higher Risk of Washer Wear: Neoprene washers can degrade over time due to UV rays and weather exposure. If the flat section is more exposed, these washers may experience faster wear and require replacement to maintain the seal.
• Shorter Fastener Lifespan on Low-Slope Roofs: On low-slope roofs, exposure to pooled water can accelerate rusting and corrosion around flat-section fasteners. Proper maintenance helps mitigate this issue.

Screws on the Rib Section

Although less common, some contractors and regions prefer to install screws on the ribs of metal roofing panels. This method focuses on driving screws into the high ridges or peaks of the panels. Here’s why this approach is sometimes used.

✅ Advantages of Screws on the Rib

• Better Water Drainage: Placing screws on the rib allows water to drain freely off the flat sections of the metal panels. This minimizes the risk of standing water pooling around fasteners, which can help prevent corrosion or leaks.
• Less Direct UV Exposure: Screws on the rib are less likely to be exposed to direct sunlight compared to fasteners on the flat. This can enhance the longevity of the washers.
• Reduced Penetration Points in Critical Areas: By avoiding screws on the flat surfaces—areas where water naturally collects—the chances of water infiltration can decrease.

❌ Disadvantages of Screws on the Rib

• Weaker Structural Grip: The ribs of a metal panel do not sit flush against the roof decking. Fasteners installed on the rib may not fully engage with the substrate, leading to a weaker hold.
• Larger Risk of Panel Shift: Over time, panel flexing during temperature changes or strong winds can loosen screws placed on the rib, causing the panels to shift or lift.
• Potential Seal Failure: Screws on the rib may not compress the washer as effectively due to the gap between the rib and the substrate, increasing the likelihood of leaks.

Industry Best Practices for Metal Roof Screw Placement

While both options have their merits, industry best practices generally favor placing screws on the flat section of the roof panels. The primary reason is improved structural stability and the ability to create a consistently watertight seal.

That said, it’s essential to consult the specific guidance provided by the manufacturer of your metal roofing system. Manufacturers may have recommendations based on the design, thickness, and type of roofing panels being used.

Tips for Proper Metal Roofing Screw Installation

Regardless of your chosen screw placement method, here are general tips to ensure a successful installation:

• Use the Right Screws: Always use screws designed for metal roofing. These screws include sealing washers that prevent leaks.
• Don’t Over-Tighten or Under-Tighten: Proper screw tension is critical. Over-tightening can damage or deform washers, while under-tightening may lead to leaks.
• Place Screws at Regular Intervals: Follow the manufacturer’s recommended screw spacing to ensure even weight distribution and prevent panel movement.
• Check for Alignment: Screws should be installed straight, not at an angle, to create a proper seal with the washer.
• Inspect Your Work: After installation, double-check fasteners to confirm they’re securely in place and that washers are properly compressed.
• Perform Regular Maintenance: Over time, check for loose screws, worn washers, and signs of rust or corrosion to maintain the integrity of your roof.

Get Your Standing Seam Metal Roof Installed Perfectly!

If you’re unsure whether to place screws on the rib or the flat, remember that most experts agree the flat section offers better overall performance. It provides stronger structural support, better watertight sealing, and reduces the risk of problems over time.

However, if you live in an area with unique weather conditions or specific manufacturer requirements, adjustments to this general rule may be necessary. Always consult a professional roofing contractor or the manufacturer for tailored advice.

At Whitt’s Quality Roofing, we specialize in metal roofing installations and repairs. If you have questions about the best practices for your roofing project or need help with installation, our team of experts is here to guide you every step of the way.

Get in touch with the team at Whitt’s Quality Roofing for reliable, high-quality service. Whether you have metal roof installation questions or need maintenance support, we’re ready to help your roof perform at its best. Contact us today!