A roof almost never fails without warning. It fails quietly for a year or two and then dramatically, and the quiet part is where a cheap fix lives.
Granules in the gutter. Asphalt shingles shed their mineral surface as they age. A few after a new install is normal. A gutter with a sandy layer in the bottom means the shingles are losing their UV protection, and the clock is running.
Shingles that look flat or shiny. That same granule loss leaves the asphalt exposed, and exposed asphalt goes glossy in the sun before it goes brittle.
Lifted or curled edges. Usually heat, sometimes poor attic ventilation cooking the deck from underneath. Either way, wind gets under a curled shingle and takes it.
Rubber boots around vent pipes. These are the shortest-lived part of most roofs — the rubber perishes and splits in under a decade, long before the shingles do. It is a cheap part and one of the most common leak sources there is.
Daylight in the attic, or a smell. Go up with a torch on a bright day and look at the underside of the deck. Any daylight is a hole. Any musty smell is moisture that has been there long enough to grow something.
Stains at the chimney or a wall junction. Flashing fails before the field does, because it moves. A rusty or lifting flashing is a repair today and a rotten deck in three years.
