SUPPORT

How to Choose the Suitable Material for Roofing Fasteners?

Time:2026-07-24

When it comes to metal roofing, the importance of fasteners cannot be overstated. While panels often receive the most attention, it is the screws and screw caps that bear the brunt of environmental exposure. Choosing the wrong material can lead to rust streaks, panel blow-offs, and costly leaks. To ensure longevity, you must match the fastener material to your specific climate and roof type.

Here is a guide to selecting between Alu-Zinc coated steel (55% Aluminum, 43.4% Zinc, 1.6% Silicon) and Stainless Steel (304 vs 316).

1. Alu-Zinc Coated Steel: The Balance of Cost and Protection

Alu-Zinc steel is a popular choice due to its excellent corrosion resistance and affordability. The aluminum provides a barrier protection, while the zinc offers sacrificial protection (galvanic action). The weight measurement (e.g., 80g, 120g, 150g) refers to the coating mass per square meter (g/m2); higher numbers mean thicker coatings and longer lifespans.

80g Alu-Zinc Steel:

Best for: Mild, dry inland climates with low pollution.

Pros: Most economical option.

Cons: Thinner coating wears out faster in harsh conditions.

Application: Ideal for interior projects or temporary agricultural structures where budget is the primary constraint.

120g Alu-Zinc Steel:

Best for: Standard residential and commercial roofing in moderate environments.

Pros: Offers a significant upgrade in durability over 80g without a major price jump. This is the industry standard for many pre-painted metal roofs.

Application: Perfect for barns, garages, and homes located away from coastal salt spray.

150g Alu-Zinc Steel:

Best for: High-humidity regions, industrial areas with mild chemical exposure, or roofs with poor drainage.

Pros: Superior corrosion resistance. The thicker coating acts as a robust shield against moisture and UV degradation.

Application: Recommended for high-end residential roofs and agricultural buildings requiring extended maintenance cycles.

2. Stainless Steel: Maximum Durability and Corrosion Resistance

Stainless steel fasteners contain chromium, which forms a passive layer of chromium oxide to prevent rust. They are significantly stronger and more expensive than coated steels but offer unmatched longevity.

304 Stainless Steel:

Best for: Coastal areas (within 5 miles of saltwater), food processing plants, and high-moisture environments.

Pros: Excellent general corrosion resistance. Resists oxidation and staining better than any Alu-Zinc variant.

Cons: Not recommended for direct contact with dissimilar metals (like aluminum panels) without isolation washers to prevent galvanic corrosion.

Application: Essential for roofs in humid southern states or near large bodies of freshwater.

316 Stainless Steel (Marine Grade):

Best for: Extreme marine environments, chemical plants, and pools.

Pros: Contains molybdenum, which dramatically increases resistance to pitting and crevice corrosion caused by chlorides (salt).

Cons: Highest cost.

Application: The gold standard for beachfront properties and critical infrastructure where.

Key Selection Tips:

Match the Panel: If your roof panels are Alu-Zinc coated, try to match the fastener coating weight to ensure both wear out at roughly the same rate.

Consider the Environment: If you live near the ocean, do not compromise on 316 stainless steel. Salt air will destroy lesser materials quickly.

Beware of Galvanic Reaction: When using stainless steel screws with aluminum panels, always use neoprene or EPDM washers to isolate the metals and prevent electrolysis.

Think Long-Term: Spending slightly more on 150g Alu-Zinc or 304 Stainless now can save thousands in future repair costs.

Conclusion:

For most standard projects in non-coastal areas, 120g Alu-Zinc coated steel offers the best value. For high-humidity or industrial zones, step up to 150g Alu-Zinc. However, if your property is near the coast, investing in 316 Stainless Steel is the only way to guarantee a roof that stands the test of time against salt corrosion.