What is Class 3 and Class 4?

Class 3 and Class 4 Roofing Fasteners

Class 3 and Class 4 are not brand names, they are coating performance requirements.

Knowing the importance, and correct use of Class 3 and Class 4 (and Class 5) fasteners, could help you choose the right fastener for your roofing projects. When the wrong class is used, it could negatively affect the lifespan of your roof.

Class 3:

The minimum grade of coating required for external applications for moderate levels of airborne pollution or coastal areas with low salt levels.

Class 4:

The minimum grade of coating required for external applications with discernible levels of airborne pollution or coastal areas with moderate to high salt levels.

ISO 9223 outlines the various corrosion categories (C1 through to C5-M) which is a determining factor for which Class of fastener to be used.

Rusted Roofing Fasteners

Corroded Roofing Screws Coming Out

Corrosion caused by using the wrong fasteners

Fasteners make up less than 3% of the cost of a building project.  But using the wrong fastener could have a significant effect on the durability of the completed project.