You should replace your roof when the damage is spread across the roof rather than confined to one area, when the shingles have reached the end of their service life, or when a hailstorm has stripped enough granules that the asphalt underneath is exposed. Age alone is not the deciding factor. The Roofing Contractors Association of British Columbia puts it directly in its consumer guide: “Age alone though, is not necessarily the best way to decide what is required. Some roofs last longer than estimated and some fail prematurely.” In Alberta the accelerating factor is almost always hail, followed by freeze-thaw cycling.
The practical test is condition, not calendar. Here is how to read the condition of your roof, and what to specify when it does need replacing.
What are the signs that a roof needs replacing?
The clearest signs are visible from the ground and from the eavestrough.
Granule loss is the first one. Asphalt shingles are protected by a mineral granule layer, and when you find granules accumulating in your gutters or at the bottom of downspouts, the shingles are shedding their UV protection. Once the asphalt below is exposed, deterioration accelerates quickly.
Curling, cupping, and cracked shingles indicate the shingle has lost flexibility. Missing shingles after a wind event, especially in clusters rather than isolated singles, point to a fastening or sealing problem across the whole roof rather than a one-off.
Bruising from hail is the Alberta-specific one and it is easy to miss. Hail damage on asphalt shingles often looks like dark circular spots where granules have been knocked away. Those spots may not leak this year, but they are the start of failure.
Sagging along a roof line, and any staining on interior ceilings or in the attic, mean water has already been getting through. At that point the question is no longer whether to replace but how much decking has to be replaced along with the roofing.
Should you repair or replace?
The RCABC consumer guide frames the decision around two factors: condition and intent.
On condition, its guidance is that if the material is still within its serviceable range, repairs may extend the useful life of the existing roof, and that “an inspection by a qualified roofing contractor or roof inspector/consultant is the best way to determine the condition of your roof.” It notes that independent inspectors charge for their service but generally produce an unbiased assessment.
On intent, the guide is equally direct: “If you intend to stay in a house until after retirement, re-roofing using a long life material such as steel panel would be reasonable. However if you intend to sell soon, it may be more cost-effective to have a good, but less expensive roof installed, or even to repair the roof if possible.”
The practical dividing line most contractors use: isolated damage on an otherwise sound roof is a repair. Damage across multiple slopes, or damage on a roof already past two-thirds of its expected life, is a replacement. Patching a failing roof buys a season and complicates the eventual tear-off.
How does Alberta hail change the calculation?
Hail is the single largest driver of roof replacement in this province, and it changes what you should install, not just when.
The City of Calgary launched its Resilient Roofing Rebate Program after the June 2020 hailstorm, one of the costliest storms in Canadian history, in which damaged roofs accounted for a large share of the loss. The program pays homeowners to upgrade to Class 4 impact-resistant roofing rather than replacing like for like.
The evidence behind that policy is quantified. A 2024 study in the International Journal of Disaster Risk Reduction, co-authored by a researcher at the Institute for Catastrophic Loss Reduction, modelled hail damage probability across five roof types: an unrated roof and impact-resistant roofs rated UL 2218 Class 1 through Class 4. Its finding: “an impact-resistant roof (impact-resistant rating classes 1 to 4) is associated with lower hail risks, with 60 % to 98 % reduction on average compared to unrated roofs.”
That is the argument for treating a hail-driven replacement as an upgrade opportunity. If you are already paying for a full tear-off, the incremental step to a Class 4 product changes the risk profile of the next storm substantially.
What is a Class 4 impact-resistant roof?
Class 4 is the top rating in the UL 2218 impact resistance standard. The equivalent Factory Mutual standard is FM 4473.
The City of Calgary’s eligibility criteria require a Class 4 rated system meeting either UL 2218 or FM 4473, and its Resilient Roofing Installation Checklist specifies what a compliant installation looks like:
- Remove the old roof covering, repair or replace damaged roof sheathing as required
- Install new material on a clean, dry, fully sealed sheathed deck, with taped seams or a fully adhered membrane
- Use continuous underlayment throughout
- Starter shingles at eave and rake edges to provide a double seal against wind
- Six nails per shingle, or as specified by the manufacturer
- Remove and replace damaged drip edges
- Install valley flashings as required
- Install ice and water shield at lower drip edges
Acceptable Class 4 materials are not limited to asphalt. The City’s list includes asphalt shingle, clay tile, concrete tile, metal, plastic and polymer composites, and recycled rubber.
Two things worth noting from that checklist. First, it mandates a full tear-off, which rules out installing over existing shingles. Second, six nails per shingle rather than the common four is a wind-resistance detail that also matters in a chinook.
How long should an asphalt roof last here?
Manufacturers rate asphalt shingles across a wide range, and the RCABC guide recommends evaluating roofing by life cycle costing, comparing the cost of the roof against the life expectancy of the material to calculate an annual cost. That framing is more useful than the headline warranty number.
What actually shortens the life of a roof in Alberta, as the guide lists, is the combination of weather (rain, wind, hail, snow, heat, freeze-thaw cycling), debris, UV exposure, and foot traffic. Southern and central Alberta deliver all of those at once. A roof that would perform to its rated life in a milder climate will typically fall short here, and hail can end it early regardless of age.
The second variable is installation quality. A correctly installed roof with proper underlayment, flashing, and ventilation reaches its rated life. A roof installed over unrepaired decking, with insufficient nails or missing ice and water shield at the eaves, does not.
What should you ask a contractor before replacing?
The RCABC guide is blunt about the risk of hiring informally: “Homeowners may be tempted to hire a ‘friend of a friend’. However well meaning the friend is, the homeowner may be left with a roof of unknown installation quality and no recourse in case of accident or future problems.”
Its checklist of what to verify: a licensed company, how long it has been in business, whether the contractor is experienced with your specific roofing material, a fixed address rather than just a cell phone, liability insurance, workers’ compensation coverage, trained employees through apprenticeship and manufacturer training programs, and basic reliability.
In Alberta there is an additional layer. The City of Calgary’s rebate requires the work be done by a contractor who is a member of the Alberta Allied Roofing Association (AARA) or the Alberta Roofing Contractors Association (ARCA) at the time of installation, or that a roof inspection report be completed by an approved AARA or ARCA inspector confirming proper product and installation. Even outside the rebate, that is a useful benchmark.
Ask specifically what happens if damaged sheathing is found during tear-off, and get the allowance in writing. That is the most common source of mid-project cost disputes.
Does insurance cover a hail roof replacement?
Hail damage is typically covered under a standard homeowner policy, but the payout structure varies. Some policies pay replacement cost, others pay actual cash value, which deducts depreciation based on the age of the roof.
Two practical points. First, document the damage with dated photos before any work begins, and have the inspection done by someone independent of the contractor bidding the job. Second, ask your insurer directly whether upgrading to an impact-resistant Class 4 product affects your premium. Given the measured risk reduction from impact-resistant roofing, some carriers price for it.
If you are in Calgary, check whether the Resilient Roofing Rebate Program is currently open before you sign a contract. The program has opened and closed multiple times, and eligibility depends on the installation meeting the checklist above, which is easier to arrange before work starts than after.
Frequently asked questions
Can I put new shingles over the old ones? Not if you want a Class 4 installation to the City of Calgary standard, which requires removing the old roof covering and repairing or replacing damaged sheathing. Beyond the rebate requirement, going over existing shingles means nobody inspects the deck underneath, so any rot or previous water damage stays hidden.
How do I know if my roof has hail damage if it is not leaking? Hail damage on asphalt shingles usually appears as dark circular marks where granules have been knocked off, and it commonly does not leak immediately. Check the eavestrough for accumulated granules and look at soft metal surfaces like vents and flashing, which dent visibly and confirm the storm was strong enough to affect shingles.
Is Class 4 roofing worth the extra cost? The modelled risk reduction is 60% to 98% compared with an unrated roof, according to the 2024 hail risk study. Whether that justifies the price depends on how long you plan to own the home and whether your insurer prices for impact resistance, but the risk difference is measured, not marketing.
Does a metal roof count as impact resistant? Metal is on the City of Calgary’s list of acceptable Class 4 materials, but the rating applies to the specific tested product rather than to metal in general. Ask for the UL 2218 or FM 4473 documentation for the exact panel being quoted.
Should I replace my roof in winter? Emergency repairs happen year round. For a planned replacement, most contractors prefer temperatures above roughly minus ten for asphalt, because shingles become brittle and the sealant strips do not bond properly in deep cold. Booking in late summer means competing with everyone else who had hail damage.
Do I need a permit to replace my roof? Like-for-like replacement generally does not require a development permit, but changes to the structure, roof line, or building envelope may. Have your contractor confirm with the municipality before starting.
Sources
- City of Calgary, Resilient Roofing and Hail (Resilient Roofing Rebate Program brochure and installation checklist): https://www.calgary.ca/content/dam/www/pda/pd/documents/hail-roofing-rebate/Resilient-Roofing-and-Hail-Brochure.pdf
- Roofing Contractors Association of British Columbia, Consumer Guide to Roofing: https://www.rcabc.org/wp-content/uploads/2025/03/Consumer-Guide-to-Roofing.pdf
- Li Y., Porter K., Goda K., “Hail hazard modeling with uncertainty analysis and roof damage estimation of residential buildings in North America,” International Journal of Disaster Risk Reduction (2024): https://media.cocorahs.org/docs/Journal_Disaster_Risk_Reduction_2024_CoCoRaHS_Hail.pdf