Exterior installations in sheet metal
Which screw to use is the best choice?

Source: Celofixings.es
Choosing the right screw for exterior installations in sheet metal and sandwich panel
Screws play a fundamental role in fixing components on sheet metal roofs, from simple accessories to structure for solar panels. However, not all bolts are created equal, and using the wrong type can lead to corrosion problems, weakening of the fastener, and ultimately property damage.
The bimetal screw
An increasingly popular option for exterior sheet metal installations are bimetal screws. These screws offer a number of significant advantages over traditional steel ones. For example, its durability against the weather is exceptional.
Stainless screws are perfect for outdoor use, but they are not capable of drilling into sheet steel, only soft metals such as aluminum. To be able to drill through steel sheets, these self-tapping screws are not stainless.
In contrast, bimetal screws are specifically designed to meet both requirements:
– The tip is cemented steel, to be able to drill through the sheet.
– The part that will be exposed to the outside is stainless, which makes them highly resistant to corrosion caused by adverse weather conditions.

Our bimetal screw for solar
Our bimetal screw comes with an EPDM washer to ensure total tightness.
CELO’s bimetal screw offers greater tensile strength compared to self-tapping screws, due to its fine thread pitch. This means more load capacity and a more secure installation, achieving a robust and durable attachment. It should be noted that, in addition, the design of its thread is specially designed to avoid maintenance and retightening of the screw.
Another notable advantage of our bimetal screw is the chip-free fastening design. Unlike self-tapping screws, which can leave shavings during installation, bimetal screws provide a solid fix without this problem. This maximizes thread utilization and ensures reliable clamping over time.
Weather durability
Total tightness
Higher tensile strength
Chip-free fastening
Common problems with exterior steel self-tapping screws
Using common self-tapping screws in outdoor installations comes with certain risks and potential problems, including:
- Corrosion: Exposure to the weather can cause corrosion of conventional steel screws, as they are not stainless steel, which can eventually weaken the attachment and cause damage.
- Low tensile strength: Self-tapping screws have a lower tensile strength in thin sheets since most of the time the sheet is thinner than the thread pitch, so the sheet vibrates between two threads.
- Ease of threading: As a consequence of the previous point, the conventional self-tapping screw is threaded earlier than our bimetal screw for thin sheets.
Common problems with exterior steel self-tapping screws

Another crucial aspect to consider is efficiency during the installation process. CELO’s bimetal screw stands out not only for its strength and durability, but also for its ability to facilitate the installer’s work. By leaving no shavings during the fastening process, this screw minimizes errors during installation, which significantly reduces material waste and optimizes time spent on the project.
On large-scale projects, where speed and accuracy are critical, this efficiency in installation can make a big difference in terms of costs and delivery times. Additionally, by simplifying the installation process, the bimetal screw allows work crews to be more productive and able to tackle multiple projects more effectively, resulting in a benefit for both contractors and end customers .
Conclusion
In short, choosing the right screw is essential to ensure the durability and safety of exterior sheet metal installations. While self-tapping screws are a common choice, our bimetal screw offers an innovative alternative with significant advantages in terms of corrosion resistance, tensile strength and long-term reliability.
By keeping these factors in mind when selecting screws for your next outdoor project, you can ensure a sturdy and durable installation that will withstand the elements and the passage of time.
Source: Celofixings.es