Why the damage is never evenly spread
Hail does not damage a roof uniformly, even though it falls on it uniformly. What decides the outcome of any single impact is what sits directly underneath the point of contact.
A hit over a soft cover board is absorbed. The same hit over a fastener plate has something hard behind it, and the sheet is broken against the plate rather than pushed into the board. A hit on the vertical face of a curb or a parapet that happened to be looking into the storm takes the force at an angle the flat of the roof never sees. A hit on a sheet that was already brittle behaves differently again.
That is why a hail survey is a mapping job rather than a sampling job. The damage clusters, and the clusters tell you something: along one elevation, over a fastener row, on every curb face pointing the same way. A handful of photographs taken from wherever the hatch happens to be tells you none of that, and it is the format most owners are handed.
It is also why the size of the stones is a poor guide on its own. Two buildings on the same street, hit by the same storm, can come out of it with completely different roofs, because one has a soft board under a thick sheet and the other has a thin sheet over plates.
What we will not tell you
We will not tell you that every dent on the roof is damage. Some are and some are not, and the difference is decided by cutting rather than by conviction.
We will not tell you the roof is fine because it is not leaking. A fractured sheet with a sound ply under it holds water out for a while, and the bill for that is deferred rather than avoided.
And we will not survey a roof for hail without first establishing that hail fell on it. That sounds obvious. It gets skipped more often than it gets done, usually by somebody who has already decided what the survey will find.
When owners call about hail
Days after a storm, when the soft metal around the building is visibly marked and somebody wants to know whether the roof took the same. Months later, after a contractor has knocked. And years later, when a roof nobody ever looked at starts leaking in a pattern that finally makes sense to a surveyor.
The cheapest of those three is the first. Nothing about a hail impact improves with time, and the record of what happened is never clearer than it is in the week afterward.
Common questions
How can hail damage a roof without causing a leak?
Because it breaks things that only leak later. Hail rarely punches a hole you can see water through on the day, and a roof that came through the next rainstorm can still be damaged.
- A fracture can run through the top plies with the bottom one still holding
- A hit over a fastener plate breaks the sheet against the plate beneath it
- Insulation can be crushed under a membrane that is still whole
- Crushed board stops carrying load and stops insulating long before it leaks
Those failures open later, when heat, cold and foot traffic work the fractured sheet until it lets go. A roof looked at after the storm gives you a list of small repairs. The same roof two summers later gives you leaks that nobody can connect to anything.
What is hail bruising, and does it always need repairing?
A bruise is a dent you can feel more easily than see, where an impact crushed what was under the membrane without visibly breaking the surface. Some need repair and some do not.
- The word came from steep slope shingles and travels badly to a membrane
- Feeling a dent proves an impact, not a breach
- What matters is whether the sheet is fractured and whether the board is crushed
- Neither is settled from the surface, so the honest test is a cut
You will be told confidently, by people who have cut nothing, that every bruise on your roof is damage. Sometimes it is. A dent with a sound sheet over it and board that has recovered is a mark, not a repair. We would rather cut a few test squares and be able to tell you which of the two you have.
Is granule loss on a modified bitumen roof hail damage?
Not by itself. Granules come off a cap sheet with age, sun, foot traffic and every heavy rain, and a roof with bare patches has usually been losing them for years.
- Hail loss is clustered, roughly circular and sharply defined
- Weathering is even and gradual, and worst where water always runs
- The test is what lies under the granules, not how many are missing
- A hit that fractures the ply felts beneath is damage, granules or no granules
The other clue is direction. Hail arrives on a slant, so its marks concentrate on the elevation it came from and on the faces of curbs and parapets that were looking into it. Loss spread evenly over the whole roof, including the sheltered parts, is telling you about the roof's age rather than about one afternoon.
Does hail damage a metal roof, or is it only cosmetic?
Both happen, and they need separating. A dent in the middle of a panel is usually cosmetic. Damage at the fixings, the flashings and the accessories is not.
- Panels dent and carry on shedding water, which is what they are there to do
- An impact that fractures the coating starts corrosion at that point
- Dents around a fastener can break the seal at the washer
- Gutters, vent caps, rooflight domes and condenser fins take the real harm
So a metal roof after hail is inspected at its details rather than photographed from a distance. Where the coating is broken, the options run from spot treatment to coating the whole roof, depending on how widespread it is. An owner should be told which of those the roof needs rather than which one is easier to sell.
Someone knocked and told us our roof has hail damage. How do we check that?
Ask them to show you, on the roof, and to say what they cut. An assertion from a driveway about a roof nobody walked is worth nothing either way.
- Ask when the hail fell, and check that against your own record
- Ask what the soft metal on the building shows, because that is cheap evidence
- Ask which findings a cut confirmed and which are surface opinion
- Be equally wary of a flat no from somebody who also did not go up
They may be right. Genuine hail damage is often invisible from the ground, and owners are also told nothing is wrong when something is. Either way the answer is a survey you can read, with locations, photographs and a note of what was confirmed. If this looks like a matter for your insurer, that record is what helps, and the next conversation is with your carrier.