GAF Timberline AS II: The Class 4 Timberline, Reviewed

There are two ways an impact rated shingle lands on a proposal. Either the homeowner asked for it, usually after a hailstorm made the subject personal, or a salesperson raised it alongside a story about insurance discounts and roofs that shrug off hail. The first is a fair question. The second is where this page earns its keep, because most of what gets said about Class 4 in a driveway is half true, and the parts that are true are more interesting than the pitch.

01 /What this page will and will not tell you

Impact ratings attract more marketing than any other shingle attribute we get asked about, so the boundary between what is documented and what is sales atmosphere matters more here than usual.

It will explain the test behind the Class 4 label in plain language, including what that test measures and what it deliberately ignores. It will give you a way to decide whether the upgrade makes sense on a house in this county, and it will hand you the exact question to put to your insurer before an impact rated roof becomes part of your budget.

It will not quote you a wind speed, a warranty length, a weight, or a dimension for AS II. Those figures belong to the current data sheet and warranty document for the exact product on your proposal, they get revised between product cycles, and a roofing website repeating a stale number is how wrong numbers survive for a decade. Where AS II may differ from its mainstream sibling, we will say the data sheet governs rather than guess either way. It also will not tell you that any insurer discounts an impact rated roof, because that is a fact about your policy and nobody here has read your policy.

02 /Where AS II sits in the Timberline family

Timberline is a family rather than a single product. The mainstream architectural shingle in it is HDZ, which is what most Macomb County proposals name by default and which we take apart in the Timberline HDZ review. AS II sits beside HDZ rather than above it. Same family, different job: the AS is the armor shield idea, and it is the impact rated member of the line.

The engineering difference, as GAF publishes it, is in the asphalt itself. A conventional architectural shingle uses standard asphalt over a fiberglass mat. An impact rated product uses a modified asphalt, rubberized with SBS polymer, which stays more pliable and absorbs a strike instead of transmitting it into a crack. That is where the rating comes from, described at the level GAF's own literature describes it. Confirm the current formulation on the data sheet for the product you are actually quoted.

03 /What Class 4 actually measures

UL 2218 is the standard sitting behind the class numbers, and the procedure underneath it is blunt in a way that is useful to picture. Steel balls are dropped onto a sample of the roof covering from a set height, in four sizes matching four classes, running from the smallest at Class 1 up to a two inch ball at Class 4, the top of the scale. Each location takes two strikes in the same spot, and that repetition is what gives the result its weight, because surviving one hit is a far easier question than surviving a second in the same place.

Then comes the part that decides everything. After the drops, the sample is examined for cracking, tearing, or rupture. The pass condition is about the mat, the structural layer that holds the shingle together and keeps water out. The standard asks one question only: did that layer fail. It has nothing to say about whether the surface still looks new.

Assessing real damage in the field is its own discipline for exactly that reason, with engineering methodologies built to separate a genuine impact bruise from the ordinary things that resemble one. The homeowner version of that skill is in what size hail damages a roof, and the most common misread we run into is in hail damage versus blistering.

04 /What the rating does not buy

• It is not hail proof. A Class 4 shingle can still be damaged, and hail large enough damages anything on a roof. The rating raises the threshold. It does not remove it.
• It is not a cosmetic guarantee. Since the test reads the mat rather than the surface, a Class 4 roof that comes out of a storm dented but uncracked has performed exactly as rated. If the look of dents would bother you, that is a conversation with your insurer, not with the shingle.
• It does nothing for the soft metals. Gutters, downspouts, vent caps, and flashing dent no matter what class the shingles carry, and on plenty of roofs those are the first thing an adjuster reads.
• It does not repair an installation. An impact rated shingle nailed above the fastening zone, or laid over reused flashing, fails in all the ordinary ways. On the same roof, correct fastening is worth more than the upgrade.
• It is not a guaranteed discount. That has its own section below, because it is where most of these conversations go sideways.

05 /The insurance credit, asked properly

The discount tends to get presented as a property of the shingle. It is not. It is a property of your policy, and the two get confused constantly.

Some insurers offer a premium credit for a documented impact rated roof and some offer nothing. Where one exists it is generally tied to documentation of the rating rather than to a brand name, and its size is set by the insurer. None of that is knowable to a roofing company, and a contractor quoting you a specific percentage off your premium is quoting a number they made up. So turn it into questions, and ask them before the tear off.

1. Do you offer a credit for a Class 4 impact rated roof, and how much is it on my policy? The answer that matters is the one for your policy, not the one in the company's brochure.
2. What documentation do you need to apply it? Usually proof of the product's rating plus an invoice. Find out what form they want it in while the job is still being planned.
3. Does the credit come attached to a cosmetic damage exclusion? This is the question nobody asks. Some policies pair an impact rated credit with an exclusion for cosmetic damage, which can mean dents that do not leak stop being claimable. That may be a perfectly fair trade, but it should be a trade you knowingly made.
4. Send it to me in writing. An agent's recollection on a phone call is not a policy term, and the endorsement is what governs.

06 /Does it pay for itself in Macomb County

The honest answer is a framework rather than a figure, because the figure depends on four things we cannot know about your house. Work through the rows and the decision usually makes itself.

WHAT IT TURNS ON	WHAT TO ACTUALLY LOOK AT	WHICH WAY IT POINTS
Local hail frequencyhow often this county really takes a hit	A record of what has actually come through, not a storm chaser's map	More real events strengthen the case
Your insurance creditif one exists, in writing	The answers to the four questions in section 05	A real credit compounds every year you own the house
Your ownership horizonforever house, or the next five years	How long you expect to be paying for this roof	A short horizon rarely recovers an upgrade premium
The rest of the scopeflashing, ventilation, decking	Whether the base proposal is already correct	Fix the base scope first, every single time

On the first row, use evidence instead of atmosphere. Our hail history field notes track what has genuinely come through this area over time, which is a better input than a flyer left in your door after a storm. Macomb County gets hail, often enough to take seriously. It is also not the hail belt, and anybody selling an upgrade on the premise that it is has told you something about their sales process.

On the last row we will be repetitive on purpose, because it is what we say about every premium option: a standard architectural shingle installed with all new flashing and working ventilation will outlast a premium shingle laid over reused metal. If the budget stretches to only one of those, the choice is not close. Choosing AS II does not move you out of the published band either. Asphalt replacement runs $9,000 to $18,000, with most homes landing between $12,000 and $16,000, and where a house lands inside it is set mostly by area, complexity, existing layers, and what the decking looks like once it is open. The wider picture is on our roof replacement page, the numbers are on the published price table, and the cost calculator runs the same bands.

07 /Certification, and where the real numbers live

Two things get promised in AS II conversations that we would rather you verify than believe.

The first is the warranty tier. GAF's enhanced coverage is not a product a homeowner can buy; it is something a manufacturer certified contractor delivers, with a qualifying accessory package on the roof and registration after the job, and the top tier is restricted further to the Master Elite level. That structure is the same for the impact rated line as for the mainstream one, and the mechanics are in the Timberline HDZ review and the GAF versus Owens Corning comparison.

The second is the fine print. You will notice no warranty duration, wind rating, step down schedule, or coverage period for AS II anywhere on this page. Not because any of it is secret, but because those figures get revised between product cycles and the internet is full of numbers that were accurate several years ago. The non prorated period, the wind terms, and the accessory requirements all sit in the current warranty document and data sheet for the specific line on your proposal. Ask your contractor for both as files before you sign. Anyone who cannot produce them has told you something useful.

A shingle rated to survive two hits from a steel ball is still relying on the person holding the nail gun. That has never once been the other way around.