FORTIFIED vs. Class 4 Shingles: What's the Difference?

• Class 4 describes a shingle product's impact rating. FORTIFIED describes a whole-roof-system standard.
• A FORTIFIED roof can use asphalt, metal, tile, or other coverings. The base standard focuses on wind performance and installation quality, not shingle impact rating.
• Impact performance only becomes a requirement if you pursue FORTIFIED's optional Hail Supplement, which is highly relevant in Minnesota due to frequent hail exposure.
• Minnesota law requires insurers to offer a discount for a qualifying FORTIFIED roof that includes the Hail Supplement—not for a base FORTIFIED designation alone. Class 4 shingles may separately qualify for a carrier discount, but through a different mechanism.
• The related state grant program has been authorized for several years but has not yet released funding.
• Neither upgrade replaces sound Minnesota-specific building science. Cold-climate performance is a separate consideration.
  

Class 4 and FORTIFIED get lumped together because they're both marketed around the same promise: a roof that survives Minnesota's hail and wind better than a standard one.

But they're not two brands of the same thing.

One is a product rating. The other is a system-level construction standard.

Understanding which is which changes how you should evaluate a quote, a discount, or a contractor's claim.

Class 4 comes from a laboratory test called UL 2218. A 2-inch steel ball is dropped onto a shingle from 20 feet, roughly simulating a 2-inch hailstone, and the shingle is checked for cracking. Products that hold up earn the Class 4 rating, the highest level in the test.



That rating tells you something meaningful about one product: the shingle. It doesn't tell you anything about how the deck underneath is attached, how the edges are finished, or how the flashing details around a chimney or valley are handled—all places where real Minnesota storms tend to find their way in.

People occasionally ask me a surprising question:

"Why would you recommend impact-resistant shingles if they may reduce the likelihood of another roof replacement after the next hailstorm?"

My answer is simple.

Because my responsibility doesn't end when the project is complete.

If I can help a homeowner avoid another deductible, another insurance claim, and another roof replacement, that's a better outcome for everyone.

If that homeowner later tells a friend or neighbor, "Call Twin City Roofing," then we've done exactly what we set out to do.

FORTIFIED, as we covered in Part 1, looks at the roof as a system: deck attachment, a sealed deck as a secondary water barrier, reinforced edges, and detailed flashing at every penetration.

A FORTIFIED roof can use several different coverings, including asphalt, metal, or tile, as long as the covering meets the wind and installation requirements of the standard.

For asphalt shingles, the base standard focuses on wind performance ratings and how the overall system is built, not on an impact rating.



That's the core distinction: Class 4 is something a product carries. FORTIFIED is something a completed roof earns, and the designation itself is verified by an IBHS-certified evaluator inspecting the whole system, not a shingle wrapper.

This is where it changes.

FORTIFIED includes an optional add-on called the Hail Supplement, and it's highly relevant here given how often Minnesota roofs take a hail hit.

If you're pursuing the Hail Supplement, the roof covering has to meet specific impact-performance criteria:

• Asphalt shingles must earn an IBHS "Good" or "Excellent" Hail Impact Rating. Current FORTIFIED standards no longer rely solely on a UL 2218 Class 4 rating for this.
• Metal, tile, and low-slope systems must meet UL 2218 Class 4 or an equivalent impact-resistance standard.

In practice, that means many FORTIFIED roofs installed in hail-prone areas like Minnesota incorporate impact-resistant roofing products because the optional Hail Supplement requires enhanced impact performance to qualify.

The base FORTIFIED designation and Class 4 shingles are technically independent of each other, but here, they frequently go together

When homeowners ask us which option is "better," it helps to step back. Every roof, regardless of product or standard, has three jobs to do.

1. Resist Impact

This is where Class 4 shingles excel. In a hail-prone state like Minnesota, impact-resistant roofing materials are one of the most practical upgrades a homeowner can make.

2. Keep Water Out

This is where the roofing system matters. In our experience, the majority of roof leaks don't begin because the middle of a shingle suddenly fails. They usually begin where different building materials come together: roof-to-wall transitions, chimneys, valleys, skylights, plumbing vents, and other flashing details.

These areas require thoughtful design and skilled installation. A premium shingle cannot compensate for poor flashing.

3. Protect the Home

Once severe weather damages a roof, the next concern becomes protecting what's underneath: drywall, insulation, flooring, and everything else inside. This is where FORTIFIED's whole-system principles become most valuable, since they're intended to reduce secondary water intrusion after a roof covering has already been compromised.

Class 4 shingles primarily strengthen the roof's first line of defense against hail impacts. FORTIFIED builds on that foundation by strengthening how the entire roofing system performs during severe weather.

If you haven't already, Part 1 walks through what a FORTIFIED roof actually is, and Part 2 covers whether it lowers your insurance premium in Minnesota.

As we discussed in Part 2, Minnesota law requires participating insurers to offer a premium discount to homeowners with a qualifying FORTIFIED roof. What's worth repeating here: the statute defines a qualifying, or "insurable," property as one designated to FORTIFIED standards that include the Hail Supplement, not a base FORTIFIED designation on its own. The scope of the discount can also vary, and it may apply only to the wind or storm-related portion of a policy rather than the full premium.

Class 4 shingles are handled differently. Many Minnesota carriers offer their own discount for Class 4 roofs, commonly in the 10-30% range, but this is a separate program from the FORTIFIED requirement and isn't guaranteed by state law the same way. As always, the only way to know what applies to a specific policy is to ask the agent directly.

Over the past several years, we've seen impact-resistant shingles perform noticeably better during many Minnesota hail events. While no roofing material is hail-proof, reducing damage frequency has real value for homeowners facing higher deductibles and repeated storm claims.

On the grant side: the state's related program, which could eventually help offset the cost of a FORTIFIED upgrade, has been authorized for several years but has not yet begun releasing funds to homeowners. We'd encourage anyone

weighing this decision to check Minnesota's Strengthen Minnesota Homes page directly for current status rather than planning around an assumed timeline.

This is where the two paths diverge again.



A Class 4 rating only tells you how a shingle performs against impact. It says nothing about how that shingle handles sub-zero flexibility, ice-dam-driven water intrusion, or attic condensation; all real Minnesota concerns that a hail lab test in a controlled environment doesn't touch.

FORTIFIED's whole-system approach, including sealed deck, ventilation, and flashing detail, is closer to addressing those northern-climate realities, but even FORTIFIED's underlying research was built largely around coastal wind and hurricane data. Applying either standard well in Minnesota takes a contractor who understands where the national standard needs local judgment.

One lesson we've learned after decades of replacing roofs in Minnesota is that craftsmanship matters just as much as product selection. Manufacturers recognize that metal flashings are among the most important components of a roofing system because they direct water away from vulnerable areas. While some existing flashings may be reused under limited conditions, manufacturers generally recommend replacing them whenever practical, and note that damage resulting from reused flashings is not covered under their warranty.



That's consistent with how we approach a reroof. It isn't simply about installing new shingles. It's an opportunity to inspect the roof deck, replace worn flashing, and rebuild the home's first line of defense against water intrusion, whether the finished roof carries a Class 4 rating, a FORTIFIED designation, or both.

For homeowners, the practical takeaway is cost versus scope: Class 4 is a lower-cost, single-product upgrade with its own discount potential; FORTIFIED is a bigger investment in the whole roof system, and it's the Hail Supplement specifically, not the base designation, that triggers Minnesota's state-backed discount requirement.



For realtors, this is worth knowing before a listing goes up. "Impact-resistant shingles," "FORTIFIED roof," and "FORTIFIED with the Hail Supplement" are three different claims, and getting them right in a listing avoids a conversation that undercuts credibility during a showing or inspection.

For insurance agents and adjusters, the distinction affects how a claim or discount request should be documented. A Class 4 shingle invoice is not the same evidence as an IBHS FORTIFIED certificate, and for the Minnesota-mandated discount specifically, that certificate needs to reflect the Hail Supplement.

The strongest roof in Minnesota isn't created by choosing between Class 4 shingles and FORTIFIED.

It's created by combining impact-resistant materials, quality craftsmanship, and a properly designed roofing system.

In our hail-prone climate, Class 4 impact-resistant shingles provide an outstanding first line of defense against the storms we experience year after year.

FORTIFIED principles can add another layer of resilience by strengthening how the entire roofing system performs during severe weather.

The right solution isn't about choosing one over the other.



It's about understanding your home's risks, your long-term plans, and selecting the combination of improvements that provides the greatest value for your family.

Every home is different, and every homeowner is weighing something different: cost, resale timing, insurability, or simply wanting the roof to hold up next time a storm rolls through.

If you're trying to decide between Class 4 shingles, a full FORTIFIED designation, or a standard reroof, we can walk you through what actually applies to your home before you commit to either.

Contact Twin City Roofing Construction Specialists Inc

Serving homeowners, realtors, and insurance professionals throughout the Twin Cities metro and surrounding Minnesota communities.

Call us today: 651-636-9640

FORTIFIED Contractor ID: R012203

Coming in Part 4:

Why Ventilation May Matter More Than Shingles in Minnesota Roofing