Did the June Hail Damage Your Flat Roof? What to Check Before Winter

The storm, briefly

On the evening of June 9, 2026, a severe storm crossed southern Manitoba under a tornado warning that covered west Winnipeg and nearby municipalities. Hail the size of tennis balls fell in Winnipeg and Sanford. Catastrophe Indices and Quantification Inc. (CatIQ) estimates the June 9–10 storms across Saskatchewan and Manitoba caused about $923 million in insured damage, and says commercial property losses drove the rise in its latest estimate.

Our post on hail and home insurance claims covers the storm and the claim deadlines in detail. This one is about flat roofs.

How hail damages each kind of flat roof

Flat roofs are not all built the same, and hail treats them differently. Here is what roofing researchers and forensic engineers report for the common types:

• Modified bitumen (SBS). Hail can knock granules loose and puncture, tear or bruise the membrane. In industry field studies after major hailstorms, modified bitumen laid directly over soft insulation was the system most prone to damage that leaks.
• Built-up and tar-and-gravel roofs. Gravel gives real protection — the more and larger the stone, the better. Where hail knocks the gravel aside, it exposes the asphalt underneath, and on insulated roofs lab tests have found fractured felts at the impact points.
• TPO and PVC. These plastic sheets generally held up well in field studies, but hail can leave circular or star-shaped fractures in the top layer, or tear the reinforcing fabric inside.
• EPDM (rubber). EPDM stretches and springs back, so it tends to shrug off hail. One manufacturer reports a 60-mil adhered membrane resisting simulated hail up to 3 inches without fracture. It is not hail-proof, though: forensic engineers find small tears that are hard to see, and dents in the insulation boards beneath.

Age matters for every type. The more weathered the roofing, the more brittle it gets and the less impact it can take. Two roofs of the same type can come out of the same storm very differently.

If a roof does need replacing, ask about hail resistance. Labs rate roof coverings by striking them with steel balls (UL 2218) or ice balls (FM 4473), and FM Approvals rates flat-roof assemblies for moderate, severe and very severe hail. A firm cover board under the membrane can make a big difference to how the roof stands up.

The damage you can’t see from above

A flat roof can look fine and still be hurt. Under the membrane on many flat roofs is rigid insulation and, often, a harder cover board. The force of a hailstone passes through the membrane into those boards.

In lab tests by Lehigh University researchers working with a manufacturer, simulated hail cracked a gypsum cover board from the inside — often on its bottom face — while the TPO membrane on top stayed undamaged. FM Approvals’ very-severe-hail test judges the whole assembly, not just the membrane, for the same reason: cover boards and insulation can be damaged by hail too.

Not every dent is a failure. Research on dented polyiso insulation found that dents alone barely changed how well it insulates. The concern is fractures — in the membrane, the felts or the boards — because fractures let water in.

Water that gets in does not always drip right away. It can spread into the insulation first. Then fall and winter do the rest: water in a crack freezes, expands by up to 9%, and widens the crack, and the next thaw lets more in. That is how hail damage on a flat roof can turn into a leak months after the storm.

Dents on the roof are evidence

The metal on a flat roof is often the best record of what fell. Soft metal is usually the first thing to show hail marks, and forensic engineers read the dents for hailstone size and direction — keeping in mind that a dent can be up to twice the size of the stone that made it.

Things worth noting from the ground, or from windows that look over the roof:

• Dented metal flashings, parapet caps and roof edges.
• Dented vent caps, exhaust hoods and scuppers.
• Flattened or pocked fins on rooftop condensers and air-conditioning units.
• Cracked skylights.
• Dents in eavestroughs, downspouts, and vehicles or equipment that were outside that night.

On commercial roofs, hail damage often develops at seams, drains, roof edges, penetrations and rooftop equipment — not just in the open field of the roof. Those are the places an inspection should look hardest.

How hail damage gets documented

A proper hail inspection on a flat roof goes past a quick walk-over. Expect some combination of:

• Photos of the whole roof and close-ups of each damaged area, with written notes on what was found and where.
• Sample cuts. Hail fractures start on the underside of the membrane, so an inspector may cut out a small piece to look at the back, then patch the cut. Samples can go to a lab to be examined under magnification.
• Moisture checks. Infrared scans and moisture meters can show whether water has already got into the insulation.
• The metal record: dents on flashings, caps, vents and rooftop units, which show how big the hail was and which way it came from.

Get it done soon. An inspection close to the storm makes a stronger record, before repairs, cleanup or more weather change what can be seen. Once snow covers a flat roof, nobody can inspect the membrane until it melts.

Reporting, deadlines and temporary repairs

Standard business insurance policies cover hail damage, including water that gets in through openings the hail made. Damage that was already there is not covered — one more reason to get the June damage on record before winter adds its own.

Manitoba’s Insurance Act writes a set of statutory conditions into property insurance policies in the province. They are not limited to home policies; commercial property policies carry them too. The short version:

1. Report the damage right away. The Act requires written notice to your insurer “immediately” after a loss, then a proof of loss as soon as practicable.
2. Two years is the deadline to sue, not to report. If a claim is denied or underpaid, you have two years from when you knew — or should have known — about the damage to start a lawsuit.
3. Stop it from getting worse. You must take reasonable steps to prevent further damage, and your insurer must contribute toward the reasonable cost. On a flat roof, that can mean a temporary repair over a known opening. Keep every receipt.

Whoever holds the building’s policy — the owner, the property manager or the condo board — should make the report. Your broker can confirm the notice clause in your own policy.

What to do this week

1. If you have not already, report hail damage from June 9, 2026 to your insurer or broker in writing. Write down the claim number, the date and who you spoke to.
2. Photograph what you can see safely from the ground or from windows: dented caps and flashings, damaged rooftop units, cracked skylights. Date the photos.
3. Walk the top floor and note any new ceiling stains or drips, with dates.
4. Book a flat-roof inspection before snow covers the roof, and ask for photos and written findings you can pass to your insurer. Call us at 204-237-8361 or send a request through our quote request form.
5. If water is coming in, call 204-237-8361 — our emergency leak response runs 24/7 — for a temporary repair, and keep the receipts.