If a supplier’s quote lists AZ60, AZ100, or AZ150 without explanation, it’s easy to assume a bigger number means better roofing. That assumption isn’t wrong. But it’s incomplete. It can lead you to overpay for protection a project doesn’t need. Or it can leave you underspecified where it matters most.
This guide explains what these numbers mean. It compares the three grades side by side. It shows how to match the right one to your project, instead of guessing. It also covers a mistake that trips up even experienced buyers: confusing AZ coating numbers with a different, similar-looking coating system.
Getting this right protects your margin and your reputation with customers. Overspecifying wastes money on protection nobody needs. Underspecifying creates warranty claims and damaged trust down the line.
What the “AZ” Number Actually Means
AZ coating: an aluminum-zinc alloy coating on steel sheet, typically around 55% aluminum and 43-45% zinc. The number after “AZ” refers to the coating mass. That’s the weight of alloy per square meter of steel, counting both sides of the sheet combined.
A higher number means the mill applied more coating material. More coating generally means a longer service life before corrosion reaches the steel underneath.
One detail catches many buyers off guard. Suppliers don’t always measure the number the same way. Some markets, mostly in North America, use an older ASTM system based on ounces per square foot. Designations like AZ50, AZ55, and AZ60 come from that system. Most suppliers exporting stone coated roofing tiles use a metric system instead. They express coating mass directly in grams per square meter, using tiers like AZ70, AZ100, AZ150, and AZ200. Always confirm which system a quoted AZ number belongs to. Two numbers that look similar can represent very different actual coating weights.
This distinction rarely comes up in casual sales conversations. Both systems use the same “AZ” prefix, and both show up as a plain number. The confusion usually surfaces only once a buyer compares two quotes side by side and the numbers don’t line up. Asking about the underlying standard upfront avoids that confusion later, once a purchase order is already close to signing.
This is especially relevant for distributors sourcing from multiple factories at once. A single spreadsheet comparing “AZ” numbers across five suppliers means nothing unless every row confirms the same measurement system underneath it.
AZ60 vs AZ100 vs AZ150 — Side-by-Side Comparison
The table below uses the metric grams-per-square-meter convention. That’s the system most stone coated tile manufacturers reference internationally.
| Grade | Coating mass | Approx. total coating thickness | Typical use case |
|---|---|---|---|
| AZ60 | ~60 g/m² | ~0.015-0.02 mm | Inland, low-humidity climates with minimal corrosion exposure |
| AZ100 | ~100 g/m² | ~0.03 mm | General residential and commercial use in moderate climates |
| AZ150 | ~150 g/m² | ~0.04-0.05 mm | Coastal, high-humidity, or industrial environments with elevated corrosion risk |
These figures are approximate. The exact number can shift slightly depending on which national standard a supplier certifies against, such as AS 1397, JIS G3321, or ASTM A792. Ask which standard applies to the specific coating mass they’ve quoted, and request the certificate that confirms it.
Salt spray test results generally track this pattern too. Lighter coatings like AZ60 typically hold up for a few hundred hours before visible corrosion appears. AZ150 coatings commonly reach 1,000 hours or more under the same test conditions. Ask your supplier for their own test results rather than treating this as a fixed rule, since coating quality and application consistency affect the outcome too.
It’s also worth asking whether the listed coating mass applies uniformly across the sheet, or represents an average. Hot-dip coating can vary slightly between the center and edges of a coil. A “minimum” coating mass specification protects you against thin spots better than an “average” specification does. This detail rarely appears on a basic spec sheet, but it’s a fair question to raise with any supplier.
Some suppliers can also provide a coating cross-section image from a lab report, showing the actual layer thickness under magnification. This level of documentation isn’t always necessary for smaller orders, but it’s worth requesting for large or repeat contracts where consistency matters most.
Why a Higher Number Isn’t Automatically the Right Choice
It’s tempting to default to the highest coating grade available, assuming more protection is always worth it. In practice, that’s not the most efficient way to specify a project.
Heavier coating adds cost, and that cost passes down the supply chain to your customer. It can also change how the sheet forms during the tile-pressing process, since thicker coatings behave a little differently under the same tooling. For a dry, inland project with minimal humidity, AZ150 doesn’t add meaningful value over AZ100. The extra cost buys protection against a corrosion risk that barely exists at that site.
The right approach matches coating grade to actual environmental exposure. Think of it the same way you’d match tile weight or wind rating to local building conditions. Basing your spec on the project’s real environment, rather than defaulting to the highest number on the price list, keeps your quotes competitive without leaving your customer underprotected.
This also shapes how you position pricing with your own customers. A buyer who understands why an inland warehouse doesn’t need AZ150 coating trusts your recommendation more. Explaining the reasoning, not just quoting a grade, becomes a real advantage as buyers increasingly compare suppliers on technical merit, not price alone.
Matching AZ Grade to Your Project’s Environment
Coating grade should track how close a project sits to the coast. Salt exposure is the single biggest factor driving corrosion speed. This lines up directly with the distance bands covered in our guide to roofing solutions for coastal and high-salinity environments.
As a general starting point:
- Beyond 15 km from the coast: AZ60 to AZ100 is typically sufficient for most inland projects.
- 5 to 15 km from the coast: AZ100 to AZ150, depending on local humidity and wind exposure.
- Within 5 km of the coast: AZ150 or higher is the safer choice, especially facing directly into onshore wind.
Local humidity matters here too, separate from distance from the coast. A humid inland climate can accelerate corrosion faster than a dry coastal one. Treat distance as a strong indicator, not the only variable worth considering. Industrial areas add another factor entirely. Airborne pollutants and chemical emissions can accelerate coating breakdown with no salt involved at all. A project near a factory zone may need a heavier coating grade, even sitting well inland.
A Common Mistake: Comparing AZ Numbers to Z (Zinc) Coating Numbers
Q: Is AZ100 the same coating weight as Z100? A: No. AZ and Z (pure zinc, galvanized) coatings use different alloys and different corrosion mechanisms. Their coating mass numbers aren’t directly comparable. An AZ coating generally outperforms a Z coating at the same numeric weight, since aluminum adds a barrier-style protection zinc alone doesn’t have.
Q: Why does this confusion happen so often? A: Both systems use a similar number-after-letter format. Both get quoted in grams per square meter in most international markets. It’s an easy detail to miss when comparing quotes from different suppliers under time pressure.
Q: What should I do to avoid this mistake? A: Ask suppliers to name the coating type explicitly, not just the number. “AZ150” and “Z150” are not interchangeable specifications, even though they look similar on a spec sheet.
What to Ask Your Supplier Before Confirming a Coating Grade
Before finalizing a purchase order, get direct answers on these points. This builds on the broader due-diligence approach in our buyer’s checklist for stone coated roofing tiles.
- Which national standard does this AZ grade certify against?
- Can you provide a salt spray test report for this specific coating class?
- Does the coating mass apply to the finished tile, or the raw coil before forming?
- Do the warranty terms change based on the AZ grade selected?
Suppliers who answer these clearly, with documentation, are worth specifying for projects where corrosion resistance genuinely matters. A supplier who can only quote the AZ number, with no standard reference or test report, is handing you a marketing figure, not a verifiable spec.
JCROOF offers multiple AZ coating grades across its tile profiles, including the Bond Tile and Shingle Tile lines. JCROOF matches the grade to project environment on request. Its project gallery includes completed installations across both inland and coastal markets.
Quick Reference: Choosing Between AZ60, AZ100, and AZ150
For a fast gut-check when reviewing a quote, three questions cover most of what matters:
- How far is the project from the coast, and which way does the prevailing wind blow? A:This sets your baseline exposure level before anything else.
- What standard is the supplier’s AZ number measured against? A:Confirm it’s the metric g/m² system common to stone coated tile exports, not the North American ASTM oz/ft² system.
- Does the supplier have a salt spray test report for that specific grade?A: A number without documentation isn’t a specification. It’s a claim.
Get these three answers before you approve a purchase order. Doing so removes most of the guesswork between AZ60, AZ100, and AZ150, and gives you a defensible reason for whichever grade you specify.
