Hail Damage on a Roof in Gilroy, CA: What Is Real and What Only Looks Like It

Hail damage to a shingle is a fracture in the mat. Everything else — lost granules, dark round marks, raised bubbles — is a different problem wearing the same clothes. That one distinction decides claims, and it is why two people can stand on the same roof and honestly disagree.

Both directions of that disagreement cost money. Real damage gets waved off as cosmetic. Cosmetic conditions get sold as damage by crews who arrived the same week as the storm and leave the same month.

What hail damage on a roof actually looks like

Haag Engineering, whose assessment protocol most adjusters were trained against, defines functional hail damage to asphalt shingles narrowly: punctures, tears, or fractures in the shingle mat. Not marks. Not color. A fracture.

On the surface that reads as an indentation with granules knocked out of it, exposing the asphalt beneath. Some are unmistakable. Many are not, and those get found by hand: press a thumb on the mark and a bruised shingle gives, softly and only there. Haag's papers describe the feel as a bruise in an apple — exactly accurate, and useless until the first time you feel one.

Why it feels soft is the part worth carrying. The fracture begins on the underside, where the impact puts the mat in maximum tension, and propagates upward toward the granules. The definitive evidence therefore sits on the side facing the deck — which is why no hail argument is ever settled by a photograph of the top of a shingle, and lifting one is the only honest way to end it.

One more tell: recently exposed asphalt is black, while asphalt exposed for months oxidizes gray. That difference is how the same protocol separates this storm from one three years ago.

Hail damage shingles: what breaks, and what only looks broken

Granule loss is the most misunderstood item here, and the correction comes from a study rather than a louder opinion.

Haag brushed measured amounts of granules off new three-tab shingles — 6, 15, 45 and 70 percent, plus one laid bare — nailed them to a south-facing 4:12 deck in Dallas and left them out for ten years. The shingle stripped of 70 percent was still shedding water at the end. Only the fully bare one eroded noticeably.

Two numbers from the same work reframe the argument. About a third of a shingle's weight is granules, and 12 to 15 percent of them had to come off before the mat was exposed at all, because manufacturers apply more than are needed to cover it. Granules are a wearing surface with slack built in.

The consequence is sharper than it sounds. If a stone stripped granules to bare asphalt but the mat underneath is intact, that shingle was already defective or already at the end of its life — a sound one struck that hard would have fractured. Hail did not take that roof's life. It found a roof that had already spent it.

Shingles are weakest where the deck does not support them — ridges, rakes, eaves, valleys — so a roof with no bruises in the field can still have broken edges along a rake.

Roof blistering vs hail damage

Start off the roof. This is the part a homeowner can settle without a ladder.

Hail comes from a direction. It dents everything soft on that side of the house at once — gutters and gutter aprons, downspouts, vent caps, fascia wrap, mailbox, the aluminum fins on the condenser. Haag's protocol treats exactly that material as evidence: spatter marks on faded metal such as condenser housings, electrical boxes and window frames, scuffs on wood fences, dents in condenser fins. Those items record the size and direction of the hailfall, and the roof's story is expected to agree with them. Concentrated, direct impacts land on the windward slope; leeward slopes get fewer, glancing ones.

Blistering dents nothing, because it never came from outside. It is gas and moisture in the asphalt expanding under heat, pushing the granule crust outward from within.

So the first question is not what the mark looks like. It is whether anything else on the property was hit, and whether the marked slopes face the storm. Clean soft metal plus marks spread evenly across every slope is a thin case for hail.

On the roof itself, the two separate cleanly.

	Hail bruise	Blister
Profile	Indented into the shingle	Raised, until the crust breaks open
Feel	Soft spot underfoot or under a thumb	Firm; a steep-sided void once open
Size	Varies with stone size	Typically a quarter inch across or less
Mat underneath	Fractured, visible from the underside	Intact
Distribution	Directional, concentrated on storm-facing slopes	Wherever the shingle ran hot, any slope
Cause	A specific dated storm	Poor-quality asphalt and heat, often within the first year

Blistering is a manufacturing condition or a heat condition, and the two are hard to separate from the roof. Haag attributes blisters to poor-quality asphalt combined with heat. The trade explanation for the heat half — widely taught, not a code position — is a poorly vented deck cooking the shingles from below, which is why blistering and inadequate roof ventilation turn up on the same houses.

Neither route is sudden and neither is accidental, which is the language a hail claim turns on. And there is a nastier interaction hiding in it: an open blister is a crust of granules over a void, so even small hail can break the crust away and expose bitumen without ever fracturing the mat. That leaves a roof covered in fresh-looking round marks after a storm that did not, in the technical sense, damage it.

Signs of hail damage on a roof, checked from the ground

None of this requires a ladder, and all of it is worth doing before you call anyone.

Look at the soft metal first. Gutters, downspouts, the gutter apron under the first course, vent caps, chimney caps, window wraps, garage doors, the condenser. Dented aluminum is the cheapest hail record you own.

Check for a direction. Walk all four sides. Hail that dented the north and west and left the south and east alone is behaving normally. Damage on every elevation equally is behaving suspiciously. Wood fences and deck rails hold hail scuffs too.

Scan the ridge and rake lines with binoculars. Unsupported edges break first, and a broken edge is visible from the ground when a field bruise is not.

Ignore the ceiling. Hail bruises rarely leak straight away. A fractured mat is a shortened life, not an open hole, and a roof can be genuinely hail-damaged over a bone-dry attic. Waiting for a stain finds storm damage two policies too late.

The four things most often mistaken for hail

Haag's inspectors, having looked at thousands of these roofs, list the same misidentifications repeatedly.

Foot traffic. Walking a hot roof pushes softened asphalt aside with the granules, leaving a raised ridge along the outer edge of the mark. Hail does not build a rim.

Adhesive spots. Sealant that dripped or bonded where it should not, then tore a round patch of granules off when the shingles separated. Dark, round, entirely innocent.

Manufacturing deficiencies. Bands or spots of missing granules or asphalt off the production line. They run in lines, which hail never does.

Age. Cupping, clawing, crazing and flaking all come from asphalt shrinking. They are frequently discovered after a hailstorm, which is not the same as being caused by one — worth remembering when someone finds them the week the storm passed.

A fifth category exists: marks made deliberately, with a hammer, screwdriver or coin. It is caught by pattern — grouped or lined up, centered on the shingle, one per shingle, high on the slope away from the edges, struck perpendicular to whatever plane the person stood on. Hail is random and does not aim.

How big the hail has to be

Small stones do less than the internet implies. In Haag's ice-impact testing, aged organic-mat shingles were damaged about half the time by one-inch stones; aged glass-fiber mat shingles took about 1.25 inches; thicker aged laminates took about 1.5 inches.

Set that against the National Weather Service threshold: a thunderstorm is severe at one inch of hail, a bar lowered from three-quarters of an inch in 2010. A severe thunderstorm warning is not a damaged-roof warning, and the two are read as one sentence in every storm-market sales pitch.

Stone density, impact angle, deck support and how brittle the shingles already were all move those numbers. Hail size sets the probability; the roof it lands on sets the outcome.

What California does and does not let you undo

Hail work moves faster than any other kind of roofing, by design. Contracts get signed in driveways within days of a storm, often before anyone has established that a single mat is fractured. What you can get out of afterward is state law, not paperwork.

California ties every cancellation window to the day you sign, not to what your insurer decides - so a denial three weeks later leaves you with no statutory way out. You get three days normally, five if you are a senior citizen, and seven only where a disaster has actually been declared by the President, the Governor or your local executive officer. The notice must be twelve-point boldface, immediately next to where you sign.

The free-roof offer, read against California law

The pitch is always a version of the same thing: sign now, insurance covers it, your deductible is handled. Notice the assumption — that the claim will pay, before anyone has lifted a shingle to look at the underside of the mat.

California has no contractor-specific rule against a roofer eating your deductible, which is unusual for a big storm state - the section listing prohibited acts in home improvement contracts says nothing about it. That is not permission. A roofer who quietly covers your share while billing the carrier the full amount is assembling a false claim, and that is a crime under Penal Code section 550 for the roofer and for you.

Bottom line

Fractured mat, or not. Everything else — granule loss, dark round spots, blisters, ridged scuffs — belongs to a different cause with a different owner. Check the soft metal for direction and stone size before you look at a shingle, expect blisters raised and bruises indented, and treat any diagnosis made from the driveway with the seriousness it earned. What insurance then does with the answer is covered in whether insurance covers a roof replacement; what a documented inspection should contain is in roof inspection cost.

Fractured mat is something you can be shown, and a slope-by-slope report that shows it settles the argument before an adjuster ever arrives. Gilroy Roof Pros produces one in Gilroy and the South Santa Clara Valley, alongside storm damage restoration, roof inspections and roof replacement. Call (888) 897-2774 — and we will also tell you when it is blistering and there is no claim to make.