When patching stops being worth it

Shingles that curl, cup or go brittle

Look along the roof from the ground at a low angle rather than straight on. Edges that lift, corners that curl upward and a surface that no longer lies flat all mean the material has lost its flexibility. Brittle shingles crack when walked on, which is why contractors stop wanting to walk them.

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.

Sagging along a line

Straight lines going wavy means something underneath has softened. That is no longer a roofing question with a cheap answer.

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.

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.

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.