Class 4 Impact Rated Roofing in Illinois: Which Product, and Whether It Is Worth It
Class 4 is the most quoted and least understood line on a roofing estimate in Illinois. Three very different materials all carry it, they earn it by different mechanisms, and the insurance credit behind it is real but voluntary. Here is how to decide which one belongs on your house.
What Class 4 is, exactly
Class 4 is the top rating in UL 2218, a laboratory test in which a two inch steel ball is dropped onto the material from twenty feet and the back of the sample is examined for cracking or splitting. A related standard, FM 4473, uses launched ice balls instead. Both are controlled impact tests on a single sample under known conditions. Neither one is a field performance guarantee, and no honest roofer or manufacturer will tell you a Class 4 roof is hail proof. What the rating reliably tells you is that the material resisted a defined impact without fracturing, which is a meaningful thing to know in a market that gets hail every few years. It is not the same thing as knowing how your roof will look after a storm.
The part almost nobody explains: two ways to pass
This is the judgment that matters, and it is the reason a comparison chart will mislead you. A Class 4 asphalt shingle generally passes by being flexible. Manufacturers add SBS modifiers, a rubberized polymer, to the asphalt so the mat absorbs an impact and deforms instead of cracking. A Class 4 composite tile passes by being tough through its thickness, a molded polymer that resists fracture outright. Metal passes by denting rather than breaking. Those are three different failure modes, and they matter after a storm. A flexible asphalt shingle can survive the test and still lose granules in a hailstorm, and granule loss is something an adjuster can and does write up. A composite tile that resists cracking does not shed granules because it has none. A metal panel that does not leak can still be cosmetically dented, and some policies specifically exclude cosmetic damage to metal. Same rating, three very different conversations with a carrier.
Class 4 asphalt: the practical default for most houses
For the large majority of homes in Arlington Heights, Mount Prospect, Palatine, Glenview and the rest of the northwest suburbs, an SBS-modified Class 4 architectural shingle is the right answer. It costs modestly more than a standard architectural shingle, it goes on with the same crew and the same details, it is repairable with materials anyone can source, and it is the version of impact resistance that pays for itself fastest. Every major manufacturer makes one. Confirm the rating by the specific product name and the specific SKU in writing, because a manufacturer's impact-rated line and its standard line often share a family name and look nearly identical on a brochure. The upgrade from standard architectural is one of the few premium decisions in roofing we recommend almost universally in this market.
Class 4 composite: what the premium actually buys
Premium composite slate and shake products from Brava, DaVinci and EcoStar carry Class 4 ratings and can be installed as part of a Class A fire-rated system, and the manufacturers publish 50-year limited warranties. The impact rating is genuinely better in character than asphalt's, because there is nothing to lose: no granules, no mat to bruise, and color carried through the tile so a chip does not show. But almost nobody buys composite for the impact rating. They buy it for the cedar or slate look without the maintenance, and the Class 4 rating is a benefit that arrives with the decision rather than the reason for it. If impact resistance is your only goal, composite is an expensive way to get it. Our head to head on the two we install most is in Brava vs DaVinci.
Metal, and the gauge footnote
Standing seam metal can carry a Class 4 rating, and whether a given system does depends on the panel gauge, the substrate and the assembly rather than on the word metal. Twenty-four gauge steel behaves differently from twenty-six. The thing to understand before specifying metal in a hail market is that the common failure after a storm is cosmetic denting rather than a leak, and cosmetic damage to metal roofing is a frequent policy exclusion. That is not a reason to avoid metal. It is a reason to read the cosmetic damage language in your policy before you commit, and to ask your agent about it in writing. Our broader comparison is in metal roof vs asphalt shingles and our standing seam guide.
What cannot be Class 4, and what that means
Cedar shake is not an impact-rated product. Wood bruises, cracks and splits under hail, and the damage from several ordinary storms accumulates in a way that shortens the roof's life without necessarily producing a leak anyone notices that season. Natural slate is extremely durable in most respects and is brittle under a point impact, so it is not where you go for impact resistance either. Neither of those is a reason not to own a cedar or slate roof, and we install both. It is a reason to know that the Class 4 conversation is one of the arguments pushing North Shore owners toward composite when a wood roof reaches the end of its life, which we covered in insuring a cedar roof on the North Shore.
What the credit is worth in Illinois, honestly
Many Illinois carriers offer a credit on the wind and hail portion of a homeowners premium for an impact-rated roof. In this market that credit has ranged roughly from the low single digits to around a quarter of the wind and hail portion, which is only part of your total premium, not all of it. It is voluntary. It varies by carrier, by policy form and sometimes by county. It can change at renewal. We are roofers and not insurance agents, and we will not promise you a discount on behalf of a company we do not work for. What we will tell you is that the credit is real often enough to be worth one phone call before you choose a shingle, and that the call is free.
What your carrier will ask you for
Plan on documentation. Carriers typically want the manufacturer's product name, the UL 2218 class, and proof the product was actually installed, which usually means the final invoice naming the specific product plus a manufacturer certificate or specification sheet. Some want photographs of the installed roof or of the product wrapper. Get all of it at the end of the job and keep it with your policy documents, because the person who asks for it may not be the person you spoke to at purchase. We provide the product documentation and a scope of work naming the specific product on every impact-rated roof we install, for exactly this reason.
When Class 4 is the wrong spend
Three situations. If you are selling within a couple of years, the credit will not accumulate to much and the buyer gets the benefit. If your carrier offers no credit at all, and some do not, then you are paying purely for durability, which may still be worth it but should be a conscious choice rather than an assumption. And if your roof has an underlying problem the upgrade does not address, which is the most common one we see, then the money belongs in the ventilation, the flashing or the deck first. A Class 4 shingle over inadequate attic ventilation still cooks from underneath. Our post on ventilation options is where that decision lives.
What it costs
For standard residential work, replacement in this market runs roughly $15,000 to $40,000 depending on size, pitch, complexity, tear-off layers and what the deck looks like underneath, with larger or more complex homes running $40,000 to $70,000. Moving from a standard architectural shingle to an SBS-modified Class 4 shingle is a modest step inside that range rather than a different category of spend, which is why we quote it as an option on nearly every proposal. For premium composite we do not publish a job total at all, because the spread across the homes we work on is too wide for a number to help. We publish the delta against the base scope on the proposal so you can see what the upgrade actually costs on your roof rather than on an average one.
Make one call before you choose
Call your agent with a specific product name and ask, in writing, what the credit is on your policy. Then decide. We will put the impact-rated option on the proposal as a priced line next to the base scope, with the documentation you will need afterward, and we will tell you if we think the money belongs somewhere else on your roof first. Leaders Roofing is family-owned, working on residential and commercial roofs across the north and northwest suburbs since 1996. Call 708-847-5418 or request a free estimate. See also our hail damage page and our roof replacement page.