Bundling the wrong fastener with metal panels puts your reputation and revenue at risk. If the fasteners aren’t right for the job, contractors make it known through returns and lost reorders. Distributors and retailers pass that dissatisfaction back up the chain, and eventually you’ll feel it on your bottom line.
Two factors should influence your choice of a construction fastener:
- Substrate compatibility
- Engineered longevity and installation performance
In this article, we’ll explore the differences between metal-to-wood and metal-to-metal roofing screws, what a quality fastener looks like, and common ordering mistakes to avoid.
What Are Metal-to-Wood Screws?
Metal-to-wood screws fasten metal panels to wood substrates like lumber purlins and roof decking. They’re the standard fastener in post-frame and residential metal roofing, as well as for light commercial buildings with wood framing.
Metal-to-wood fasteners commonly use a Type-17 point, a notched tip that cuts into wood fibers rather than forcing them apart. The notched design reduces splitting and makes the screw easier to start. The point pierces the metal panel first, then bites into the wood beneath.
The thread design is coarse and deep. Wood is a softer, more fibrous material than steel, so the threads need to be wider and more aggressive to develop adequate pull-out resistance.
What Are Metal-to-Metal Screws?
Metal-to-metal fasteners use a self-drilling point rather than a self-tapping one. The tip is shaped like a small drill bit that cuts its own hole through steel, eliminating the need for a pre-drilling step.
The drill point capacity needs to match the gauge of steel being fastened. A point rated for light-gauge steel won’t penetrate heavy-gauge purlins, and an overly aggressive point on thin steel can over-drill the steel and fail to develop thread engagement. Thread design is finer than on wood screws, because steel requires tighter thread engagement to hold.
Why Fastener Longevity Matters
Building owners expect a metal roof to last 40 years or more. Standard painted fasteners will perform adequately in many situations, but paint can chip during installation or degrade from UV exposure. For projects where longevity is a priority, zinc-cast heads offer a meaningful step up.
Atlas’ Wood Ultimate and Metal Ultimate fasteners feature a Zamak-5 zinc alloy cast head, warranted against red rust for the life of the building. That’s the kind of spec to look for when the goal is a fastener that lasts as long as the panels.
Common Mistakes When Ordering Metal Roofing Fasteners
Specifying the Wrong Screw for the Substrate
The most common ordering mistake is failing to confirm what the panels will be fastened to. Metal-to-wood and metal-to-metal screws are engineered for fundamentally different substrates. Ship the wrong type, and your buyers are stuck with fasteners that don’t perform as expected.
Mismatching Fastener Life to Panel Life
If the panels are rated for a multi-decade lifespan, the fasteners should be too. Instead of commodity screws, choose premium construction fasteners engineered to match the service life of the panels they’re securing.
Ordering the Wrong Fastener Length
Fastener length has to account for everything the screw passes through: panel thickness, insulation, and the substrate itself. Total stack-up thickness varies from job to job, and it’s easy to get wrong when panel profiles, underlayment, or decking thickness change between projects.
Read our guide to screw length and thread engagement to learn more.
Choose the Right Roofing Fasteners for the Job
Selecting the right fastener isn’t complicated: match the screw to the substrate and the roof’s expected service life. For projects where longevity matters, Atlas’ Long-Life Fastener line is engineered to last.
Explore Atlas’ full range of metal-to-wood and metal-to-metal fasteners to find the right fit for your application.
