G90 Galvanized Steel Roofing — 2026 Technical Guide (ROOFNOW™ Pillar Post)

This technical guide explains G90 galvanized steel, the industry standard for Canadian metal roofing. Metallurgy, zinc protection, corrosion resistance, and winter durability are covered in detail. This guide supports Ontario homeowners by linking the ROOFNOW™ service site at roofnow.ca and the educational Knowledge Center at new.roofnow.ca/blog.

1. Overview

G90 galvanized steel is the premier substrate for Canadian metal roofing systems due to its corrosion resistance, zinc coating thickness, and ability to withstand harsh winter cycles. ROOFNOW™ uses G90 exclusively for Ontario installations. More metallurgy resources are available at new.roofnow.ca/blog.

2. What Is G90 Galvanized Steel?

G90 steel is carbon steel coated with 0.90 ounces of zinc per square foot (both sides). This zinc layer protects the steel substrate from rust, oxidation, and environmental exposure.

3. Zinc Coating Thickness & Protection

Zinc provides three layers of defense:

• Barrier protection — isolates steel from moisture
• Cathodic protection — zinc sacrifices itself to protect exposed steel
• Self-healing edge protection — slows rust formation on cuts and scratches

4. Manufacturing Process

G90 steel is produced using a hot-dip galvanization method where steel is submerged in molten zinc. It passes through air knives that regulate coating thickness, then receives primer and topcoat layers such as SMP Crinkle Finish.

5. Corrosion Resistance in Canada

Canada’s climate presents:

• High snow load moisture
• Freeze-thaw cycling
• Spring humidity
• Acidic rainfall

G90’s zinc layer provides the required corrosion resistance for long-term roof performance.

6. Winter Performance

G90 steel does not crack, delaminate, or become brittle during extreme winter temperature shifts. Snow-shedding behaviour improves roof safety and prevents load stress.

7. Salt & Ice-Melt Resistance

Ontario roads use heavy chloride salts, which can accelerate corrosion in lower-grade metals. G90 withstands chloride exposure far better than G40 or G60 steel.

8. G60 vs G90 vs Galvalume®

G60 Steel

• 0.60 oz zinc per ft²
• Not recommended for Canadian climates

G90 Steel

• 0.90 oz zinc per ft²
• Industry standard in Ontario

Galvalume®

• Aluminum-zinc alloy
• Good corrosion resistance but scratches show more visibly

9. Canadian Building Standards

G90 steel meets or exceeds structural and exterior exposure requirements in Canadian building codes and CSA standards.

10. Why G90 Steel Is Used for Roofing

Benefits include:

• Long-term durability
• Corrosion resistance
• Strong winter performance
• Edge protection on cuts
• Compatibility with premium coatings like SMP Crinkle

11. SMP Crinkle Finish on G90

SMP Crinkle Finish adds:

• Scratch resistance
• Improved snow shedding
• Better UV protection
• Long-term colour retention

12. Lifespan Expectations

A G90 steel roofing system typically lasts 50–75 years, depending on installation quality and weather exposure. More installation guidelines can be found at roofnow.ca.

13. Maintenance

G90 metal roofs require minimal maintenance:

• Clear debris annually
• Inspect flashing
• Maintain clean gutters

14. Environmental Benefits

G90 steel is recyclable, reduces landfill waste, and requires fewer replacements compared to asphalt shingles.

15. ROOFNOW™ Crosslink Summary

This guide supports Ontario homeowners by connecting technical roofing science on the Knowledge Center with practical installation insights on the main ROOFNOW™ site:

Main Website (Installation & Estimates): https://roofnow.ca

Knowledge Center (Guides, Research & Encyclopedia): https://new.roofnow.ca/blog