When investing in a stone coated metal roof, understanding the quality grades is crucial for making an informed decision that balances performance, longevity, and cost. The quality is primarily defined by three core parameters: the colored sand, the adhesive, and the aluminum-zinc-coated substrate. At Cosmos Metal, we provide transparent information to help you choose the perfect roof for your project.

1. Core Parameters: The Foundation of Quality

The durability, safety, and environmental friendliness of stone coated metal roofing tiles are directly determined by the quality of their core components. Adhering to standards like China's JC/T 2470-2018 and international ISO/ASTM regulations, products are generally classified into three grades: A (Top Standard), B (Medium Standard), and C (Qualified Standard).

Colored Sand: The surface layer must resist UV rays and weathering. High-grade, high-temperature sintered ceramic sand offers permanent color stability, while lower-grade dyed sand is prone to fading.

Adhesive: This binds the sand to the metal substrate. Premium pure acrylic resin can withstand extreme temperatures (-40°C to 200°C), whereas inferior adhesives risk sand loss and cracking.

Aluminum-Zinc Coating: This is the primary corrosion barrier. The weight of the zinc layer is a key indicator of lifespan, with Grade A requiring ≥100g/㎡ and Grade C often having ≤40g/㎡.

The following table summarizes the core parameter requirements for the three grades:

2. Grade A: The Top-Tier Standard

Raw Materials & Characteristics:

Substrate: Features a fingerprint-resistant aluminum-zinc steel sheet with a zinc coating ≥100g/㎡. The optimal 55% Al-43.4% Zn-1.6% Si alloy composition provides exceptional corrosion resistance, passing 1000 hours of salt spray testing (ISO 9227).

Colored Sand: Utilizes high-temperature sintered ceramic sand (e.g., French Berre stone), ensuring permanent color stability (ΔE ≤3 per ASTM G154-16). It also offers excellent noise reduction (≥30 dB) and is environmentally safe (RoHS compliant).

Adhesive: High-viscosity pure acrylic resin withstands extreme temperatures (-40°C to 200°C) and demonstrates superior wear resistance (Taber abrasion loss ≤50mg), preventing sand loss even in harsh climates. It is low in VOC emissions.

Technical Standards & Certs:
Grade A products meet the highest international and domestic benchmarks, including JC/T 2470-2018 Grade I, ISO 9227:2017 salt spray test, ASTM G154-16 UV aging, and GB 8624-2012 Class A non-combustible rating.

Application & Cost:

Ideal for: High-end villas, landmark buildings, and corrosive environments (coastal, high-UV areas).

Life-Cycle Cost: With minimal maintenance, the annual cost is less than $0.5 per square meter, offering superior long-term value.

3. Grade B: The Balanced, Cost-Effective Standard

Raw Materials & Characteristics:

Substrate: Zinc coating weight between 40-100g/㎡, meeting basic JC/T 2470-2018 standards. Corrosion resistance is moderate, with no obvious corrosion in 500-hour salt spray tests.

Colored Sand: A blend of sintered and dyed sand. Color fastness (ΔE ≤5) is good, though slight fading may be visible after about 5 years.

Adhesive: Modified acrylic resin with a temperature resistance of -30°C to 150°C. It performs well in most conditions but may be prone to local cracking in persistently hot and humid climates.

Technical Standards & Certs:
Compliant with JC/T 2470-2018 qualified product standards, passing GB/T 1771 salt spray test (≥7 grade) and 100 hours of artificial weathering (GB/T 1766).

Application & Cost:

Ideal for: Ordinary residential and commercial buildings in non-harsh environments.

Economic Balance: Over a 30-year period, the average annual cost is approximately $0.8-$1.0 per square meter, representing excellent cost-effectiveness.

4. Grade C: The Qualified, Budget-Conscious Standard

Raw Materials & Characteristics:

Substrate: Zinc coating is typically ≤40g/㎡, offering basic corrosion resistance. Rust spots may appear in salt spray tests within 240 hours.

Colored Sand: Primarily uses non-baked, dyed sand, which is prone to significant fading (ΔE >8) within 1-2 years and algae growth.

Adhesive: Often uses lower-grade resins that can crystallize at -20°C and are prone to bubbling at high temperatures, with a high risk of sand shedding.

Technical Standards & Limitations:
Meets only the minimum threshold of JC/T 2470-2018. It has limitations in water resistance and fire rating (typically B1), and may carry higher environmental risks regarding VOC emissions.

Application & Cost:

Usage Risks: Higher maintenance costs, with a potential need for partial replacement after 5 years. The total life-cycle cost can exceed that of higher-grade products.

Ideal for: Temporary buildings or low-budget renovation projects where long-term performance is not the primary concern.

5. Cost Comparison & Selection Guide

The following table compares the overall cost differences:

Our Selection Recommendations:

For Harsh Environments, Choose Grade A: In coastal, high-altitude, or industrial areas, the high initial investment in Grade A pays off with a 50-year, maintenance-free service life, offering the lowest total cost of ownership.

For Best Value, Choose Grade B: For most standard residential and commercial applications, Grade B provides an excellent balance of quality, performance, and cost, fully complying with national standards.

Consider Grade C for Short-Term Needs: We only recommend Grade C for temporary projects or where the budget is the absolute primary constraint, with a clear understanding of its performance limitations.

You Get What You Pay For
The principle of "you get what you pay for" in stone coated metal roofing is evident in the corrosion resistance of the substrate, the color longevity of the sand, and the weather resistance of the adhesive.

Cosmos Metal is Your Trusted Partner
At Cosmos Metal, we can supply high-quality stone coated metal roofing products across these grades to meet your specific market demands and project requirements. Customization is our most flexible service—contact us today to find the perfect roofing solution.