You’ve just spent a small fortune on a new metal roof for your house. It’s supposed to last decades, so you want to make sure it’s installed properly. One thing that’s often overlooked is the screws - they may seem insignificant, but the wrong screws can lead to rust and corrosion, compromising your roof way before its time.

Many metal roofing screws only offer class 4 corrosion resistance, but that’s not going to cut it. With all the rain, sun and pollution, your roof is exposed to some harsh elements. You need screws with a superior corrosion resistance rating to handle whatever is thrown at them. Otherwise, those tiny screws become your roof’s weak point, rusting out from underneath the panels and jeopardising the whole structure.

Don’t get screwed over by skimping on the screws - for a metal roof that lasts, class 4 screws just won’t do.

Understanding Corrosion Resistance Ratings for Metal Roofing Screws

When it comes to metal roofing screws, a class 4 corrosion resistance rating just won't cut it. These screws may seem fine at first, but over time, they'll start to rust and corrode, jeopardising the integrity of your roof.

For metal roofs, you need screws with a class 5 corrosion resistance rating or higher. Class 5 screws are made of high-quality stainless steel or similar alloy designed specifically for use with metal roofing. They can withstand decades of exposure to rain, sun and weather without corroding.

Some key things to know about corrosion resistance ratings:

  • Class 1-3 offer minimal protection and will corrode quickly. Avoid these.
  • Class 4 screws use a basic coating that helps for a few years but will eventually break down. Not ideal for permanent roof installation.
  • Class 5 or higher (the higher the better) use special alloys and coatings to prevent rust and corrosion even after long-term exposure. These are best for metal roofs.
  • The rating is based on salt spray chamber testing. The higher the class, the more hours of exposure without significant corrosion. Class 5 is typically 500-1,500 hours.
  • Higher corrosion resistance means a higher upfront cost, but it will save you money, time and hassle down the road. It's a worthwhile investment for your roof.

Don't make the mistake of skimping on corrosion resistance for your metal roof screws. For the best long-term performance, choose class 5 or higher screws. Your roof will stay securely in place and looking its best for decades to come.

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Why Class 4 Corrosion Resistance Is Not Enough for Metal Roofs

If you're installing a metal roof, don't settle for Class 4 corrosion resistance screws. While Class 4 may seem durable enough, the truth is they won't stand up to the elements in the long run. Here's why you should opt for higher grade, longer-lasting screws:

  • Class 4 screws only have a zinc coating, which provides basic protection but will eventually corrode, especially if exposed to moisture. Once the zinc coating is compromised, the screw will rust from the inside out.
  • Metal roofs can last 40-70 years, so the screws need to be equally durable. Class 4 screws will start rusting in 3-5 years, meaning you'll have to pay for replacement and repairs long before your roof's lifetime is up.
  • Higher grade screws like Class 5 or stainless steel offer superior rust resistance through specialised coatings and alloys. Stainless steel screws are ideal for metal roofs in coastal areas or places with high humidity.
  • It may cost slightly more upfront, but using highly corrosion-resistant screws will save you money, time and hassle in the long run. Your roof will perform better, last longer, and avoid premature failure.

Don't cut corners and regret it later. For metal roofs, only highly durable, rust-proof screws will do. Your roof is a big investment, so take the time to choose proper fixings that will stand the test of time. The minimal added cost will be worth the peace of mind and longevity. Use screws with at least Class 5 level corrosion resistance, or stainless steel for the best protection. Your roof will thank you!

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Opting for Class 5 Roofing Screws: The Importance of Superior Corrosion Resistance

Opting for Class 5 Roofing Screws: The Importance of Superior Corrosion Resistance

When it comes to metal roofing, the screws you use are just as important as the panels themselves. Cheaper screws may seem like a good way to save a few quid, but they often lack the corrosion resistance needed for long-lasting roof performance.

Class 4 screws, while common, offer only basic protection against rust and corrosion. Over time, exposure to moisture and weather will cause them to deteriorate, damaging your roof panels and shortening the life of your metal roof.

Instead, choose screws with a Class 5 rating or higher. These screws have special coatings like ceramic or polymer that create an impenetrable barrier against the elements. They can last as long as your metal roof panels, ensuring your roof stays securely fastened for decades.

Spending a bit more upfront on high quality, corrosion-resistant screws will save you money, time and hassle down the road. Class 5 screws prevent rust streaks and leaks, and avoid the need for difficult screw replacement. Your roof will maintain its sleek, uniform appearance for longer.

When installing a metal roof, durability and longevity are key. Don’t get screwed over by choosing inferior fasteners. For the best protection, specify roofing screws with a Class 5 corrosion resistance rating or better. Your metal roof—and your wallet—will thank you in the long run.


You've now seen why it's so important not to cut corners when it comes to the screws and fasteners on your metal roof. Class 4 corrosion resistance may seem like it offers decent protection, but as you've learned, it won't withstand the test of time and weather. For a roof expected to last 40-50 years, you need screws with a higher corrosion resistance rating to avoid premature rusting and failure. Spend a little extra upfront for class 5 or even stainless steel screws and you'll save yourself the headache and cost of repairs down the road.

Your roof is a big investment, so don't get screwed over by skimping on the details. Do it right the first time and choose screws as durable and long-lasting as your metal roof panels. You'll be glad you did.