How to tell a roof is past repairing

Shingles that curl, cup or go brittle

A roof near the end goes hard. Shingles that were pliable enough to seal down in the sun no longer bond, and the first serious wind takes them.

Sagging along a line

A ridge or a plane that dips is a structural signal rather than a covering one. It usually means decking that has been wet long enough to lose strength, and occasionally framing. This is the one symptom that should not wait.

Repeated repairs in different places

One leak is an event. Three leaks in three different areas inside two years is a pattern, and the pattern means the covering has reached the end of its service life rather than suffered a specific failure.

The age on the paperwork

If the roof is over twenty years old and made of asphalt, an inspection is worth doing whether or not it is leaking. The failure modes above are much cheaper to catch before the water arrives than after.

Granules in the gutter

Asphalt shingles are protected by a granular surface. When that surface starts washing off in quantity, the mat underneath is exposed to ultraviolet and the clock speeds up sharply. A handful of granules after a new roof is normal shedding. Cupfuls, years later, is not.

Daylight or damp in the attic

The attic tells the truth earlier than the ceiling does. Staining on the underside of the deck predates any stain you will see downstairs by a long way.

In short

If two or more of these apply, get somebody to look at it and give you a remaining-life number in years. That single number turns the decision from a worry into arithmetic.