Windshield Rock Chips: What Alberta's Glass Endorsement Deletes

A stone comes off the truck ahead of you somewhere on Stoney Trail in February, and there is a sound like a knuckle on a window. By the time you are parked there is a star in the glass the size of a shirt button, sitting just high enough to be in your eyeline. The question every Calgary driver asks next is whether this is an insurance problem or a wallet problem, and the answers available to them are remarkably poor: American blogs about states that legislate free glass repair, brokers describing what “most policies” do, and a great deal of confident advice from people who have never opened the form.

The form is free. Alberta does not leave auto policy wording to the market. The Superintendent of Insurance approves the standard policy and every endorsement, each form is footed with that approval, and all of them are published as PDFs anybody can download. That is why this article can quote the words themselves rather than describe what policies generally say. On 14 September 2026 we read six of those documents end to end: the policy, both editions of the glass endorsement, both of the province's vehicle inspection manuals, and the Vehicle Equipment Regulation. What they describe is not a vague grey area. It is a very specific piece of drafting, and once you have seen it you cannot unsee it.

The base policy already names the thing that breaks your windshield

Comprehensive cover in Alberta is defined in Section C, Subsection 3 of the Standard Owner's Automobile Policy as cover “from any peril other than by collision with another object or by upset”. That is broad on its own, and the policy then goes further. It lists a set of causes that “shall be deemed loss or damage caused by perils for which insurance is provided under this subsection 3”, and among them sits the phrase that settles the argument: “missiles, falling or flying objects”.

A stone thrown up by a passing truck is a flying object in the plain sense of the words, and the drafters put the phrase there so that nobody would need to litigate it. This is worth stating clearly because the folklore runs the other way. The baseline position in this province is not that windshield damage is an awkward exclusion an owner has to fight about. On the approved form, with Comprehensive purchased and nothing else attached, a rock chip is inside the coverage. Everything interesting happens because of a separate document.

Fourteen listed causes, and a stone is not one of them

Alberta approves an endorsement called AB-S.E.F. No. 13(D), the Limitation of Glass Coverage Endorsement. It is one page. Its operative sentence reads: “The Insurer shall not be liable under Subsection 3 - Comprehensive of Section C - Loss of or Damage to Insured Automobile for loss or damage to glass unless such loss or damage is caused by:” — and then it enumerates. The list is closed, and it is short enough to reproduce in full:

Read it once for what is there and the list looks generous. Read it again for what is missing and the shape of the thing appears. Hail is covered. Earthquake is covered. The forced landing of an aircraft is covered, and so is the derailment of the train your car was riding on. The phrase the base policy went out of its way to include — missiles, falling or flying objects — is the one that does not come across. In the province where a stone off a gravel-treated highway is the ordinary way a windshield gets damaged, that is the single cause the endorsement does not carry.

One item in that list deserves separate attention, because it cuts the other way from how people usually read a vandalism clause. The fourteenth item preserves cover for “vandalism to windows other than the front window”. So where the endorsement is attached, your side glass is still protected from a vandal and your windshield, specifically, is not — even though base Comprehensive deems malicious mischief a covered peril for the whole car.

The list is Specified Perils wearing a different name

The fourteen causes are not a bespoke standard somebody wrote to describe glass risk. Put them beside Subsection 4 of the same policy — Specified Perils, the cheapest tier of physical damage cover Alberta sells — and they line up almost exactly. Specified Perils names eleven causes. The endorsement is those same eleven, plus the vandalism carve-out, plus two more added in 2022.

That is the clearest way to describe what the endorsement actually does. It does not invent a special regime for windows. It quietly moves your glass down from Comprehensive to something very close to Specified Perils while the rest of the car stays where it was. Specified Perils is built around discrete catastrophic events rather than the ordinary attrition of driving, which is exactly why hail survives the transition and the stone does not. We should be careful not to overreach here: no document in this set explains the drafting, so this is an account of where the words came from rather than a claim about anyone's intentions.

They revised it in 2022, and the stone still did not make the list

Alberta publishes the superseded edition of this endorsement next to the current one, which makes the revision visible. The older S.E.F. No. 13d — headed “COMPREHENSIVE COVER - LIMITED GLASS (FOR ALTA., NUNAVUT, N.W.T. AND YUKON)” — lists twelve causes. The current form, footed (06/2022), lists fourteen. The two additions are impact with a live undomesticated animal, and another automobile striking your car while it is not in use or operation.

Both were already handled by the base Comprehensive wording, and the revision brought them across so that glass would keep them as well. Which is to say the list was deliberately widened. That is what makes the omission worth dwelling on. Somebody opened this endorsement, concluded its list was too narrow, widened it by two, and did not add the falling or flying object. After 2022 it is difficult to characterise the gap as something nobody had got around to looking at.

Each chip is its own claim

There is a clause in the policy that reshapes glass damage even for drivers with no glass limitation at all, and almost nobody does the arithmetic on it. The Deductible Clause provides that each occurrence “shall give rise to a separate claim in respect of which the Insurer's liability shall be limited to the amount of loss or damage in excess of the amount deductible, if any, stated in the applicable subsection”.

A storm is ordinarily treated as a single occurrence: however many panels and however much glass it damages, it happened once, and one deductible applies. The policy never defines the word occurrence, so that treatment is ordinary practice rather than something the text settles. Three stones picked up on three different drives across a winter are three occurrences, and each is a separate claim with the deductible applied to each. This is why chip damage behaves so unlike every other kind of damage a Calgary car accumulates: the economics are driven by how the damage arrives rather than by how much of it there is. For a great many owners it means small glass damage was always going to be self-funded, endorsement or no endorsement — which is a different and more useful thing to know than whether you are technically covered. The same single-event logic is why hail, the common Calgary peril the endorsement does keep on its list, sits in a completely different financial category from the gravel that hits you all winter.

Alberta's two inspection manuals disagree by one millimetre

Separately from insurance, the province publishes standards for when a windshield is bad enough to fail an inspection — and it publishes two of them, which do not agree. The Automotive & Light Truck Vehicle Inspection Manual, the one covering cars and light trucks, rejects a windshield with “cracks, or blemishes more than 12 mm (1/2 in) in diameter in the area swept by the wipers, excluding the area under the inside mirror and a strip 75 mm (3 in) in the upper and lower parts of the windshield”. The Commercial Vehicle Inspection Manual rejects “a chip that is larger than 13 mm in diameter within the area swept by OEM windshield wipers”.

Two things to take from this rather than one. The obvious one is that the province maintains two standards for the same defect on the same highways, one millimetre apart, one measuring “blemishes” and the other measuring “chips” — and machine-checked, the word chip does not appear anywhere in the passenger manual. The more useful one is that both measure inside the area swept by the wipers, so where the damage sits does as much work as how big it is. A substantial chip out at the edge of the glass can pass a standard that a smaller one directly in front of the driver fails.

Neither figure is a repair-versus-replace rule, and neither is an insurance threshold. They answer only whether a windshield passes when somebody is required to inspect it, which for an ordinary registered passenger car in Alberta is not a routine annual event. It is worth being precise about this because millimetre figures travel badly. The ones published by lease-end lenders are a different domain again: as we found reading six lenders each drawing the glass line at a different millimetre, those are contractual wear-and-tear standards set by whoever financed the car, not Alberta inspection criteria, and the two sets of numbers should never be read as one scale.

Calgary manufactures this exact damage

The City is unusually open about what it puts on the road. Between 0 and -14 degrees Celsius it uses rock salt and salt brines. Below -15 degrees with colder weather forecast, it switches to what it calls Pickle — a sanding chip mixture that is 3 per cent salt and 97 per cent gravel — together with liquid calcium chloride. Separately, and across the whole season rather than that temperature band, it applies roughly 40,000 to 50,000 tonnes of road salts a year.

Ninety-seven per cent gravel is the number to sit with, and it is worth being precise about what it describes: it is the composition of the mixture described above, not a description of the road surface once that mixture is down. What it establishes is simply that Calgary's cold-weather answer to ice is to put loose stone on the road on purpose. That is the mechanism behind the endorsement's omission mattering here more than it would almost anywhere else: the cause the form declines to carry across is the cause this city generates industrially. We are not going to put a rate on it. No document publishes how quickly a windshield accumulates chips and we have not measured one.

What to actually do

Find your Certificate of Automobile Insurance, not the policy booklet, and look for AB-S.E.F. No. 13(D) or the older S.E.F. No. 13d by form number. The booklet is the standard wording everybody receives; the certificate records what was sold to you. Check it per vehicle rather than per policy, because the endorsement contains a blank reading “this endorsement applies only to the automobile(s) described under item(s) number” — on a household with a daily driver and a weekend car, the two can sit on different footings.

Two limits on what we have told you, both of which matter. The endorsement operates on Subsection 3 by its own words, and SPF No. 1 separately sells Subsection 1 - All Perils; no document we read addresses how the two interact, so we are not going to guess on your behalf. And Comprehensive is optional to begin with, so a policy that never carried it was never going to respond to a stone regardless of any endorsement. Both are questions for the party that will actually pay or decline the claim, and both are better asked before the next stone than after it.

Then, separately, decide what to do about the glass itself. If your windshield sits outside Comprehensive, the cost of the next one is entirely yours, and that changes the arithmetic on prevention far more than anything we could say about the product. That is the honest case for the film that keeps the loss from happening in the first place — it does not alter a word of what an approved endorsement says, it does not repair glass that is already chipped, and it only addresses the impact. If you want the numbers behind a modern replacement before deciding, our guide to what a HUD-and-ADAS windshield actually costs to replace sets them out. And if it is the paintwork rather than the glass you were worried about, the same policy treats the two quite differently — we covered how the same policy treats the paint rather than the glass separately, and the conclusions do not transfer.