GAF Timberline AS II Review: Hail Performance in Minnesota Reroofs

The GAF Timberline AS II — short for Architectural Shingle II — has become one of the most-installed Class 4 impact-resistant asphalt shingles in the Twin Cities over the past several years. In our shop’s reroof tracking, AS II accounts for roughly 35% of the Class 4 installs on Minnesota homes that qualify for an insurance premium discount. The reasons: it’s available, it’s compatible with the rest of GAF’s system warranty, and it actually performs in real-world Minnesota hail events the way the lab testing predicts.

If you’re researching gaf timberline as ii review information because your insurance company is asking about Class 4 options, your contractor recommended it, or you saw it on a comparison shopping list, this guide covers what AS II actually is, how it differs from non-rated Timberline products, where it lands against competitor Class 4 options, and what it costs in our market.

At Owl Roofing in Shoreview we install Timberline AS II several times a month and have walked enough post-storm AS II roofs to have a clear opinion on its real-world performance. Noah Bergland heads our roofing division and reviews each Class 4 spec on premium reroofs personally. This guide reflects what we’ve actually seen on Minnesota roofs, not the manufacturer’s marketing brochure.

TL;DR

What AS II actually is

AS II is built on the same Timberline HDZ profile that GAF sells as their volume architectural shingle, but the asphalt mat is modified with a polymer (typically SBS — styrene-butadiene-styrene) that gives the shingle elastomeric properties. When hail impacts a standard architectural shingle, the asphalt mat fractures and granules fly off — eventually exposing the fiberglass scrim underneath. When hail impacts a polymer-modified mat, the rubber-like polymer absorbs the impact energy and the shingle bounces back rather than fracturing.

The visible difference between standard Timberline HDZ and AS II is minimal — same color palette, same shadow line, same install footprint. The functional difference shows up only under impact testing or in real-world hail events. GAF publishes the full product specs on their site.

Hail testing: what UL 2218 and FM 4473 actually mean

Test	What it measures	Class 4 threshold
UL 2218	Steel ball drop simulating hail impact	2″ diameter ball, 17 ft drop, no rupture
FM 4473	Ice ball impact at controlled velocity	2″ ice ball, 90 ft/sec, no penetration

AS II passes both. The UL 2218 Class 4 rating is what most insurance companies reference for premium discount eligibility in Minnesota. UL publishes the test methodology if you want the technical detail.

Critical caveat: lab testing uses ideal projectiles. Real hail varies in shape, density, velocity, and impact angle. Class 4-rated shingles handle most Minnesota hail events well but aren’t immune to severe storms. A 2.5″ hailstone hitting at 100 mph can damage any asphalt shingle, Class 4 or not. The rating is a meaningful upgrade in resistance, not a guarantee of immunity.

Real-world Minnesota performance

We’ve walked AS II roofs after the major Twin Cities hail events of the past few years. The pattern is consistent: AS II roofs typically show no functional damage from hail under 1.5 inches and limited cosmetic damage from hail 1.5–2 inches. Above 2 inches, all shingles take damage including Class 4, but AS II tends to keep more granules and resist more cracking than standard architectural products.

The most useful comparison is between adjacent homes that took the same storm. Standard architectural shingles often need full replacement after a moderate hail event; AS II on the next-door home usually shows enough wear to qualify for an insurance claim but rarely requires replacement. The marginal cost of AS II vs standard Timberline pays back the first time the home takes a hail event large enough to claim against.

Insurance discount eligibility in Minnesota

Most major Minnesota insurers offer a 10–25% discount on the homeowner’s insurance premium for installing Class 4 impact-resistant shingles. The exact discount varies by carrier and by region. Common Minnesota carriers offering the discount include State Farm, Allstate, American Family, Liberty Mutual, and several smaller regional companies.

To claim the discount you typically need:

• A copy of the manufacturer’s certification letter showing UL 2218 Class 4 rating
• A copy of the install contract specifying the product
• A photo of the manufacturer’s wrapper from the install (some carriers require this)

Our Class 4 insurance discount guide walks through the documentation process for the major Minnesota carriers.

Cost vs competitor Class 4 shingles

For a typical 25-square Twin Cities reroof:

• GAF Timberline AS II: $4.00–$5.50 per sq ft installed
• CertainTeed Northgate ClimateFlex: $4.20–$5.80 per sq ft installed
• Owens Corning Duration FLEX: $4.10–$5.60 per sq ft installed
• Malarkey Vista AR / Legacy: $4.30–$5.90 per sq ft installed

The cost spread between Class 4 brands is small — typically within $0.30 per sq ft of each other. The bigger variable is the warranty and system pairing. If your roof is going to use GAF underlayment, ridge cap, and starter, AS II makes sense as the field shingle. If you’re committed to CertainTeed or Owens Corning system warranties, their Class 4 product is the natural fit.

AS II vs Duration FLEX vs Northgate ClimateFlex vs Malarkey

Each of the four major Class 4 asphalt shingles in our market has a different design approach:

GAF AS II

SBS-modified asphalt mat. Lower granule weight than some competitors but consistent UL 2218 Class 4 performance. Best when paired with GAF’s Golden Pledge or Silver Pledge warranty system.

Owens Corning Duration FLEX

Polymer-modified mat with a slightly different polymer chemistry. Heavier shingle than AS II. Strong cold-weather flexibility, which matters in Minnesota. Compatible with Owens Corning’s lifetime warranty system. Our Duration FLEX vs AS II comparison covers the head-to-head.

CertainTeed Northgate ClimateFlex

Highest granule weight in the category. Strong UV resistance. Pairs with CertainTeed’s SureStart Plus warranty for full-system installations. Slightly higher install cost reflects the heavier shingle weight.

Malarkey Vista AR / Legacy

Uses recycled tire rubber as the polymer modifier. Strongest cold-weather performance in our experience because the rubber stays flexible at lower temperatures than synthetic polymers. Available in fewer colors than the GAF/CertainTeed/OC options. Our Malarkey vs GAF comparison covers the trade-offs.

When to choose AS II vs alternatives

Choose AS II when:

• You’re installing a complete GAF roofing system and want warranty consistency
• Your contractor is a GAF Master Elite installer with the strongest warranty pricing
• You want a balance between cost and performance — AS II is competitively priced
• Color or style preference aligns with GAF’s palette

Choose a competitor Class 4 when:

• Cold flexibility is your priority (Malarkey, Duration FLEX)
• You want maximum granule weight and UV resistance (Northgate ClimateFlex)
• You prefer the warranty terms of a different system (CertainTeed SureStart, OC lifetime)
• You’ve had positive results with a specific brand on a previous roof

Common AS II install issues to watch for

The Class 4 rating only holds if the install hits all the wind-zone details: hand-sealed starter strips on rakes and eaves, factory storm-tab adhesive on every shingle, and ring-shank nails driven flat. We see AS II roofs underperform when the installer ran the same crew rhythm they’d run for a basic three-tab. The shingles aren’t the problem — the install is.

Specific items to verify on a Class 4 install:

• Hand-sealed starter on rakes and eaves (manual sealant bead in addition to factory tab adhesive)
• Six-nail pattern in high-wind zones (vs. standard four-nail)
• Ring-shank nails driven flat — not over-driven or under-driven
• Manufacturer-spec underlayment system (GAF FeltBuster or Tiger Paw under AS II for system warranty)
• Manufacturer-spec ridge cap (TimberTex or Seal-A-Ridge for GAF system warranty)

What real homeowners say

“Owl installed AS II on our Edina home four years ago. We had a hail event last summer that hammered the neighborhood — every neighbor with standard shingles filed a claim. Our roof had minor granule loss, no functional damage. Insurance discount has saved us about $400 a year. The math on Class 4 has paid off.” — John Wharton

What Owl Roofing Customers Actually Say

Real, verified Google reviews from real customers Owl Roofing maintains a 5.0 Google rating with 30+ five-star reviews.

Noah is the real deal. After our insurance denied our roof claim and the first roofer walked away, Noah showed up the next day and said he thought he could get us a new roof. He delivered. He got us a roof covered by insurance after it had already been declined. We came up with a nickname for him: “The Roof Whisperer.”

— Tyler Moberg, verified Google review

I am an Independent Insurance Agency owner and have worked with Noah on several roof projects. The homeowners have been extremely satisfied with the quality of work and craftsmanship Noah and his crews have provided. From filing the claim to replacing the roof and cleaning up the job site, Noah and his crew are the best!

— Fred Zappa, Independent Insurance Agency Owner

We used Owl Roofing for a repair on our roof in Brooklyn Park, and I was blown away by how good they were. Every member of the team communicated well about the process. Their price transparency was super helpful. They got the work done very fast, and the team was professional and very kind.

— Matt Brown, Brooklyn Park (verified Google review)

Noah and his team are outstanding! His clear communication, professionalism, and workmanship are top-notch. I recommend Owl Roofing to all my clients, friends, and family.

— Christine Westlund, verified Google review

It didn’t feel like dealing with a big company — it felt like working with people who actually care about the homes and community in the North Oaks and Shoreview area. Great people, great communication, and really solid work.

— Cody Warren, verified Google review

Frequently asked questions

What is GAF Timberline AS II?

It’s GAF’s Class 4 impact-resistant version of their Timberline architectural shingle. Uses polymer-modified asphalt for hail resistance. Carries UL 2218 Class 4 and FM 4473 ratings.

Does AS II qualify for the Minnesota insurance discount?

Yes, with most major insurers. Discount typically 10–25% on the homeowner’s insurance premium. Your contractor provides the manufacturer certification letter as documentation.

How much does Timberline AS II cost?

$4.00–$5.50 per sq ft installed in our market for a typical reroof. Premium colors and complex roofs run higher. The marginal cost over standard Timberline HDZ is roughly $0.40–$0.80 per sq ft.

Is AS II better than Duration FLEX or Northgate ClimateFlex?

All three perform similarly in real-world Minnesota hail events. Choose based on system warranty preference, contractor specialization, and color/style fit. AS II is the right choice for a GAF system; the others fit their respective ecosystems.

Does AS II warranty include the impact-resistant performance?

Limited to manufacturer’s stated terms — GAF’s standard Timberline warranty applies, with additional impact-resistance coverage requirements specific to the AS II product. Read the certificate carefully.

Where to start

If you’re planning a Class 4 reroof in the Twin Cities and considering AS II, the right step is a contractor walk and a system spec. The Class 4 product is only as good as the install detail and the system pairing.

Request a free Owl Roofing quote and we’ll write a Class 4 spec including AS II as one option. You can also explore our Class 4 insurance discount guide, our Duration FLEX vs AS II comparison, our Malarkey vs GAF comparison, our roofing services, and our brand library.