Age is a weak signal
The first question most people ask is how old the roof is. It is the wrong starting point. A twenty-two-year-old roof over a dry, well-vented attic on a north-facing slope can have years left; a twelve-year-old roof over a sealed soffit and a bathroom fan venting into the attic can be finished. What decides the answer is whether the failure sits in one place or shows up everywhere.
Localized failure: repair
A repair makes sense when you can draw a circle around the problem and the rest of the roof outside that circle looks healthy. Typical candidates:
- A handful of shingles torn off in a windstorm, with the surrounding field still flexible and holding its granules.
- Flashing that has pulled away or rusted at a chimney, a sidewall or a plumbing stack boot that has cracked. Boots are a common failure and usually the first thing to go.
- A valley that was detailed poorly and is leaking in one spot.
- Damage from a branch, a satellite dish mount or a previous trade walking where they should not have.
Matching colour on a repair is a lost cause after a few years of weathering. That is cosmetic, and it should not drive a decision to replace an otherwise sound roof.
Systemic failure: replace
When the same symptom appears in unrelated places, you are looking at the material reaching the end of its service life, not at an event. Signs that the whole plane has gone:
- Granules collecting in the gutters and at the bottom of downspouts every time it rains, with shiny dark patches visible on the slope.
- Shingles curling at the corners or cupping in the middle across a whole elevation.
- Tabs that crack when flexed instead of bending, meaning the asphalt has lost its oils.
- Repairs that keep moving: fix one leak and another appears a metre away the following season.
- Daylight visible through the sheathing from inside the attic, or decking that feels springy underfoot.
What is under the shingles matters more
Two structural facts change the calculation regardless of surface condition.
The first is layer count. Many provinces and municipalities permit a limited number of roofing layers; a second layer over the first is common, a third is generally not allowed and in any case hides the deck and loads the structure. If the roof already carries two layers, the next job is a tear-off, and patching into it is throwing money at a surface you will remove anyway.
The second is the deck. Soft, delaminated or water-stained sheathing has to be replaced, which can only happen with the covering off. A roof with a compromised deck is never a repair, no matter how good the shingles look.
When a storm is involved
Hail and wind damage follow their own process. Photograph everything from the ground before any work is done, including the date, and look at soft metals such as gutters, vents and flashing, where hail impacts are easiest to read. Call your insurer and let them set the sequence of inspection. Emergency measures to prevent further damage are normally expected of you; a full replacement authorised by a contractor before the adjuster has looked is a good way to end up arguing about it.
A reasonable way to decide
Ask the person on the roof three questions and listen to how specific the answers are. How many layers are up there. What condition is the sheathing in where it has been opened. Is the attic ventilation adequate, and what did they see when they went in. Someone who answers those three from direct observation is giving you information. Someone who answers from the driveway is giving you an opinion.
If the answers point to a surface that is worn out across the board, replacing the whole plane at once is both simpler and less disruptive than staging it. If they point to one bad detail, fix the detail and get the remaining years you paid for.