When patching stops being worth it

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

When the leaks stop clustering and start appearing anywhere, you are not fixing a fault any more. You are paying for a replacement in instalments, at a worse rate.

Granules in the gutter

The granules are the sunscreen. Losing them in volume means the asphalt beneath is being cooked directly, and from that point the roof ages in years rather than decades.

The age on the paperwork

Age alone is not a reason to replace. Age plus any one of the symptoms above usually is.

Daylight or damp in the attic

Go up on a bright day with the lights off. Pinpoints of daylight through the deck, dark staining on the sheathing, damp insulation or rust running down a nail shank all say water is getting in and has been for a while.

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.